IPAC2018 - List of Keywords (simulation)

Paper	Title	Other Keywords	Page
MOPMF006	Test of Stepwise Electron Bunch Replacement in eRHIC Using an Electron Lens in RHIC	electron, emittance, proton, experiment	95
	W. Fischer, M.R. Costanzo, A.V. Fedotov, X. Gu, A. Marusic, M.G. Minty, C. Montag, Y. Tan, P. Thieberger BNL, Upton, Long Island, New York, USA
	Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy. The electron-ion collider eRHIC requires an electron bunch replacement about every second to maintain both high luminosity and polarization. If the bunch can be replaced in several steps, the requirements for both the electron gun and the electron accelerator are greatly reduced due to the reduced bunch charge. However, a stepwise replacement of electron bunches in eRHIC will give rise to transient effects from the beam-beam interaction that will lead to emittance growth. Such a scheme was tested using one of the RHIC electron lenses with a multiple step increase of the electron current. The test provides an order-of-magnitude estimate of the effect without any further mitigating measures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF006
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MOPMF010	Measurement and Simulation of Betatron Coupling Beam Transfer Function in RHIC	coupling, betatron, experiment, quadrupole	99
	Y. Luo, W. Fischer, A. Marusic, M.G. Minty BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Transfer function measurements are important for characterizing betatron tunes, betatron coupling, and beam spectrum in the routine operation of the Relativistic Heavy Ion Collider (RHIC). To counteract the linear betatron coupling, we developed a technique to continuously measure the betatron coupling coefficient with a base band phase lock loop tune meter in 2006. Based on this technique, we demonstrated and built a robust tune/coupling feedback in RHIC. In this article, we revisit the BTF measurement with betatron coupling to benchmark our BTF simulation code. We also compared the values of eigenmode projection ratios from BTF with those calculated with the single particle model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF010
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MOPMF011	Beam-Beam Issues With Two Interaction Points in eRHIC	proton, electron, detector, luminosity	102
	Y. Luo, M. Blaskiewicz, A. He, C. Montag, V. Ptitsyn BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In this article, we study the beam-beam interaction related issues with two interaction points in the current eRHIC ring-ring design. We carried out strong-strong beam-beam simulation in a 2-d bunch intensity scan. We observed coherent beam-beam instability and emittance blowup with 2 collisions per turn at lower bunch intensities than the case with only 1 collision per turn. To deliver collisions to the two experiments simultaneously, we proposed a new bunch filling pattern to avoid 2 collisions per turn for any electron or proton bunch. We proved that the parasitic beam-beam effect with the new bunch filling pattern is negligible.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF011
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MOPMF012	Study of Crabbed Collision in eRHIC With a Combination of Strong-Strong and Weak-Strong Simulations	electron, proton, cavity, luminosity	105
	Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the present design of the future electron-ion collider eRHIC at the Brookhaven National Laboratory, a crossing angle of 22~mrad between the electron and proton orbits at the interaction region is adopted. To compensate the geometric luminosity loss, a local compensation scheme with two sets of crab cavities for each beam is considered. In this article, we first carry out strong-strong beam-beam simulation to study possible coherent beam-beam instability. Under the assumption of no coherent beam-beam motion, we then carry out a weak-strong beam-beam simulation to determine the long-term stability of the proton beam with the equilibrium electron beam sizes extracted from the strong-strong beam-beam simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF012
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MOPMF014	Polarization at eRHIC Electron Storage Ring, an Ergodic Approach	polarization, electron, lattice, storage-ring	112
	F. Méot BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Based on considerations of ergodicity of the dynamical system of an electron bunch at equilibrium, the preservation of polarization in an electron storage ring is estimated from the tracking of a very limited number of electrons. This has a substantial impact on required High Power Computing resources, in noticeable contrast with the method generally used that tracks tens of electron bunches, each comprised of thousands of particles, for several thousands of turns. It is also shown that a minimum number of tracking turns is required in order to ensure the numerical convergence of the linear regressions that yield depolarizing time constant values from tracking, in both methods.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF014
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MOPMF018	Numerical Simulation of Spin Dynamics with Spin Flipper in RHIC	resonance, dipole, polarization, injection	118
	P. Adams, H. Huang, J. Kewisch, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Spin flipper experiments during RHIC Run 17 were performed to study its effectiveness as a method for polarization sign reversal during stores. Numerical simulations are reported here, which were performed in accompaniment of these, and are being pursued with the aim of accurately reproducing the experimental conditions and providing thorough insight in the role of various key parameters participating in the dynamics of the spin flip, such as the sweep rate of the AC dipole, chromatic orbit control at RHIC snakes, RF parameters, possible effects of non-linear spin resonances, mirror resonance, tolerance on flipper magnet parameters, etc. The ultimate goal is for these simulations to serve as a guidance toward perfect flip to allow routine use during physics Runs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF018
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MOPMF022	Luminosity Reduction Caused by the Full-Detuning LLRF Scheme on the HL-LHC Crab Cavities	luminosity, cavity, proton, LLRF	129
	E. Yamakawa, R. Apsimon, A.C. Dexter Cockcroft Institute, Lancaster University, Lancaster, United Kingdom P. Baudrenghien, R. Calaga, F.J. Galindo Guarch CERN, Geneva, Switzerland
	The High-Luminosity LHC (HL-LHC) crab cavities (CCs) will be installed on both sides of IP1 (ATLAS) and IP5 (CMS) to compensate for the geometric luminosity reduction due to the crossing angle. To cope with the increased beam current (0.55 A DC for LHC, 1.1 A for HL-LHC), the operation of the LLRF system has been changed: rather than fully compensating the transient beam loading, we allow the phase to vary along the turn (100 ps peak-peak with 1.1 A DC). This has been implemented at LHC since July 2017. The CCs have high loaded Q (5e5) and the available RF power is insufficient to follow the bunch phase modulation. The crabbing voltage is not modulated, causing a phase error w.r.t. the individual bunch centroids, leading to transverse kicks of the centroids and an asymmetric crabbing of the bunch cores. We present an analytical model for the resulting luminosity reduction and validate with particle tracking simulations. Due to the symmetry of the bunch filling patterns for the counter-rotating beams, the peak luminosity is reduced by only 2% for nominal HL-LHC parameters at IPs 1 and 5, which is within tolerable limits.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF022
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MOPMF028	A Superconvergent Algorithm for Invariant Spin Field Stroboscopic Calculations	resonance, polarization, storage-ring, lattice	145
	D. Sagan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: National Science Foundation and the Department of Energy Stroboscopic averaging can be used to calculate the invariant spin field \bfn for particles with a finite oscillation amplitude in phase space. The standard technique starts with making a guess for \bfn(\bfr), which is a function of the phase space position \bfr. By tracking a particle's orbital position forward in time and then projecting the guessed \bfn backwards to the starting phase space point, the average of the backward projected spins will converge to the invariant spin direction linearly as 1/N where N is the number of turns tracked. The convergence can be accelerated by an iterative method that uses an approximate invariant spin field constructed by averaging the calculated spin field over points that are close in orbital phase space. This superconvergent algorithm has been built into a new program based upon the Bmad toolkit for charged particle and X-ray simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF028
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MOPMF038	Cleaning Performance of the Collimation System with Xe Beams at the Large Hadron Collider	collimation, betatron, heavy-ion, proton	176
	N. Fuster-Martínez, R. Bruce, P.D. Hermes, J.M. Jowett, D. Mirarchi, S. Redaelli CERN, Geneva, Switzerland
	The LHC heavy-ion program with Pb ions has delivered substantial physics results since the startup of the LHC. There was a Xe run in 2017 in which collimation losses and cleaning were assessed. These studies give a unique opportunity for very valuable benchmark of simulation models with measurements, which could also be very important to understand limitations for future runs with Pb and other species. In this paper, we present collimation loss maps measured in the first ever operation of the LHC with Xe ions. The measurements are compared with simulations and first conclusions are discussed for possible future operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF038
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MOPMF040	Crossing Angle Anti-Leveling at the LHC in 2017	luminosity, operation, proton, experiment	184
	N. Karastathis, K. Fuchsberger, M. Hostettler, Y. Papaphilippou, D. Pellegrini CERN, Geneva, Switzerland
	In 2017, LHC incorporated in operation an anti-leveling procedure of adapting in steps the crossing angle of the colliding beams to increase the integrated luminosity. In this paper, we present the Dynamic Aperture simulations that were employed to identify the operational margins, and therefore define the leveling steps. The results are complemented by observations from nominal operation and projections for the 2018 operation. Additional anti-leveling techniques, investigated in dedicated machine studies are also discussed
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF040
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MOPMF043	Tuning of CLIC-Final Focus System 3 TeV Baseline Design Under Static and Dynamic Imperfections	luminosity, ISOL, collider, linear-collider	196
	E. Marín, A. Latina, J. Pfingstner, D. Schulte, R. Tomás CERN, Geneva, Switzerland J. Pfingstner University of Oslo, Oslo, Norway
	In this paper we present the tuning study of the Compact Linear Collider - Final Focus System (CLIC-FFS) 3~TeV baseline design under static and dynamic imperfections for the first time. The motion of the FFS magnets due to ground motion and the impact of active and passive mechanisms envisaged to stabilize both e^- and e⁺ systems are described. It is found that the Pre-isolator required for stabilization of the Final Doublet drives the performance of the collider at the final stages of the tuning process. The obtained tuning performance depending on the stabilization techniques are discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF043
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MOPMF044	New Coordination Tools to Prepare Programmed Stops in the LHC and its Injectors	hardware, MMI, dipole, FEL	200
	S. Chemli, M. Bernardini, T.W. Birtwistle, A. Bolognesi, B. Brito Da Palma, S.E. Bustamante, J. Coupard, K. Foraz, E. Kleszcz, N. Kotsolakos, T. Krastev, P. A. Kulig, Y. Muttoni, B. Nicquevert, L. Pater, A. Patrascoiu, S. Petit, C. Rauser, A. Wardzinska CERN, Geneva, Switzerland
	The LHC and its Injectors are submitted to an overall lifecycle of three to four years of physics delivery to Experiments with a two-year long stop, also known as Long Shutdown (LS). The years of physics delivery are ended by a programmed stop for the immediate preventive and corrective maintenance, also known as (Extended)-Year-End Technical Stop - (E)YETS. This regular cycle is to be addressed in parallel with other projects: the upgrade projects to the accelerator complex of the LHC (High-Luminosity project) and to its Injectors (LHC Injectors Upgrade), and the "standard" consolidation tasks. This paper describes the way the programmed stops coordination group prepares the activities to take place during the stop with a set of new tools and processes that ease the communication between the stakeholders of the coordination.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF044
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MOPMF046	Simulation of Hydrodynamic Tunneling Caused by High Energy Proton Beam in Copper through Coupling of FLUKA and Autodyn	target, proton, collider, coupling	204
	Y.C. Nie, A. Bertarelli, F. Carra, C. Fichera, L.K. Mettler, R. Schmidt, D. Wollmann CERN, Geneva, Switzerland
	For machine protection of high-energy colliders, it is important to assess potential damages caused to accelerator components in case large number of bunches are lost at the same place. The numerical assessment requires an iterative execution of an energy-deposition code and a hydrodynamic code, since the hydrodynamic tunneling effect will likely play an important role in the beam-matter interactions. For proton accelerators at CERN and for the Future Circular Collider (FCC), case studies were performed, coupling FLUKA and BIG2. To compare different hydrocodes and not to rely only on BIG2, FLUKA and a commercial tool, Autodyn, have been used to perform these simulations. This paper reports a benchmarking study against a beam test performed at the HiRadMat (High-Radiation to Materials) facility using beams at 440 GeV from the Super Proton Synchrotron. Good agreement has been found between the simulation results and the test as well as previous simulations with FLUKA and BIG2, particularly in terms of penetration depth of the beam in copper. This makes the coupling of FLUKA and Autodyn an alternative solution to simulating the hydrodynamic tunneling. More case studies are planned for FCC and other high-beam-power accelerators.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF046
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MOPMF055	Update of the CLIC Positron Source	positron, target, linac, electron	236
	Y. Han, L. Ma SDU, Shandong, People's Republic of China C. Bayar Ankara University, Faculty of Sciences, Ankara, Turkey S. Döbert, A. Latina, D. Schulte CERN, Geneva, Switzerland
	The baseline positron source of CLIC has been optimised for the 3 TeV c.o.m. energy. Now the first stage of the CLIC is proposed to be at 380 GeV. Recently, the positron transmission efficiency from the tungsten target to the damping rings injection has been improved by 2.5 times. This opened the possibility for an optimisation of the whole positron source, comprising the injector linacs, aimed at improving its performance and its overall power efficiency. In this paper the key parameters of the positron source, which include the current and the energy of the primary electron beam, the thickness of the crystal and amorphous tungsten targets, the distance between the two targets, the adiabatic matching device (AMD) and pre-injector linacs, are optimized to improve the overall power efficiency.
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MOPMF062	Upgrade of the Dilution System for HL-LHC	kicker, operation, Windows, damping	261
	C. Wiesner, W. Bartmann, C. Bracco, M. Calviani, E. Carlier, L. Ducimetière, M.I. Frankl, M.A. Fraser, S.S. Gilardoni, B. Goddard, T. Kramer, A. Lechner, N. Magnin, A. Perillo-Marcone, T. Polzin, E. Renner, V. Senaj CERN, Geneva, Switzerland
	The LHC Beam Dump System is one of the most critical systems for reliable and safe operation of the LHC. A dedicated dilution system is required to sweep the beam over the front face of the graphite dump core in order to reduce the deposited energy density. The High Luminosity Large Hadron Collider (HL-LHC) project foresees to increase the total beam intensity in the ring by nearly a factor of two, resulting in a correspondingly higher energy deposition in the dump core. In this paper, the beam sweep pattern and energy deposition for the case of normal dilution as well as for the relevant failure cases are presented. The implications as well as possible mitigations and upgrade measures for the dilution system, such as decreasing the pulse-generator voltage, adding two additional kickers, and implementing a retrigger system, are discussed.
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MOPMF068	Quantum Excitation due to Classical Beamstrahlung in Circular Colliders	collider, photon, emittance, radiation	281
	M.A. Valdivia García, D. El Khechen, K. Oide, F. Zimmermann CERN, Geneva, Switzerland
	In the collisions of proposed future circular colliders, like FCC-ee and CEPC, the beamstrahlung regime is classical, i.e. with an "Upsilon parameter" much smaller than 1. In the classical regime, for a constant electromagnetic field a simple relation exists between the average photon energy u and the average squared photon energy u², which is the same as for standard synchrotron radiation in storage rings. This relation breaks down, however, if the electromagnetic field is not constant in time and position, as is the case for a beam-beam collision. We derive an analytical expression for u²/u², considering the case of Gaussian-bunch collisions with crossing angle (and possibly crab waist). We compare our result with the photon energies obtained in beam-beam simulation for FCC-ee at beam energies of 45.6 GeV and 175 GeV, using the two independent codes BBWS and Guineapig. Finally, we re-optimize the FCC-ee parameters of a possible mono-chromatization scheme for direct Higgs production at 125 GeV, derived previously, by applying the refined expression for the rms photon energy.
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MOPMF070	High Voltage Design for the Electrostatic Septum for the Mu2e Beam Resonant Extraction	cathode, high-voltage, vacuum, extraction	289
	M.L. Alvarez, C.C. Jensen, D.K. Morris, V.P. Nagaslaev, H. Pham, D.G. Tinsley Fermilab, Batavia, Illinois, USA
	Two electrostatic septa (ESS) are being designed for the slow extraction of 8GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage components that affect the performance of the septa. The components under consideration are the high voltage (HV) feedthrough, cathode standoff (CS), and clearing electrode ceramic standoffs (CECS). Previous experience with similar HV systems at Fermilab was used to define the evaluation criteria of the design of the high voltage components. Using electric field simulation software, high E-field intensities on the components and integrated field strength along the surface of the dielectric material were minimized. Here we discuss the limitations found and improvements made based on those studies.
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MOPMF085	Beam-gas Background Characterization in the FCC-ee IR	scattering, background, vacuum, optics	322
	M. Boscolo, O.R. Blanco-García INFN/LNF, Frascati (Roma), Italy H. Burkhardt, R. Kersevan, M. Lueckhof CERN, Geneva, Switzerland F. Collamati INFN-Roma1, Rome, Italy
	The MDISim toolkit is used to evaluate and characterize the beam-gas induced background in the FCC-ee Interaction Region. MDISim allows a full characterization of this beam background source with the locations where the beam-gas scattering occurs as well as the loss points, as a function of different vacuum conditions and composition, for the nominal optics and parameters. Detailed pressure distribution profiles have been obtained running coupled synchrotron radiation and molecular flow montecarlo codes, as an input to the GEANT4 calculations. The particles hitting the pipe in the IR can be tracked in the detectors with a full Geant-4 simulation. Semi-analytic estimates for the expected rates and lifetime are also performed.
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MOPMF090	First Studies of Ion Collimation for the LHC Using BDSIM	collimation, hadron, heavy-ion, proton	341
	A. Abramov, S.T. Boogert, L.J. Nevay, S.D. Walker JAI, Egham, Surrey, United Kingdom
	At the Large Hadron Collider (LHC) at CERN ion physics runs are performed in addition to proton physics runs. In ion operation the cleaning efficiency of the collimation system is lower than in the case of protons and the ion showering process is more complicated and produces a larger variety of secondary particles. In particular, lighter ion species can be produced as fragmentation products in the collimation system and specialised physics lists are required to simulate their production and propagation in matter. The Geant4 toolkit offers comprehensive physics process lists that extend to the case of arbitrary ion species at high energies. First results from a study of ion collimation for the LHC using the Geant4 physics library in BDSIM are presented here. These include simulations of a full ring loss map and particle spectra for collimator leakage for a Pb beam at injection energy in the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF090
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MOPMK010	Study Progress of the Coupling Resonance of the Crab Crossing Scheme in Electron-Ion Collider	luminosity, electron, synchrotron, cavity	368
	Y. Hao FRIB, East Lansing, USA Y. Luo, V. Ptitsyn BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). The bunch length effect of the ion beam cannot be ignored even when cooling is present compared with the wavelength of the crab cavity, therefore, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence an impact to the luminosity lifetime. In this paper, we present the result of numerical beam dynamics studies of the crab crossing scheme. The result indicates that there is a special coupling resonance in the nonlinear relation of the crab crossing scheme of the EIC, which dominates the luminosity degradation. And we will discuss the possible remedies for such resonance.
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MOPMK012	Electron Cloud Studies in FCC-ee	electron, collider, quadrupole, vacuum	374
	E. Belli Sapienza University of Rome, Rome, Italy P. Costa Pinto, G. Rumolo, T.F. Sinkovits, M. Taborelli CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy
	Electron cloud effects are one of the most critical aspects for the LHC and the future circular colliders. In the frame of the electron-positron collider FCC-ee, an estimation of the electron cloud build up in the machine will be discussed in this paper. A preliminary evaluation of the heat load in the arc components and interaction region magnets will be presented, together with possible mitigation strategies.
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MOPMK016	Calculations of Beam-Beam Effect and Luminosity for Crab Dynamics Simulations in JLEIC	luminosity, collider, electron, beam-beam-effects	386
	H. Huang, V.S. Morozov, A.V. Sy JLab, Newport News, Virgina, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contracts DE-AC05-06OR23177 and DE-AC02-06CH11357. Crab crossing is an integral part of the Jefferson Lab Electron-Ion Collider (JLEIC) design to achieve high luminosity while meeting the detection and physics pro-gram requirements. The crab crossing scheme provides a head-on beam-beam collision for beams with a nonzero crossing angle. Simulations of crabbing dynamics currently do not include beam-beam effects. We describe a framework for accurate simulation of beam-beam effects on crabbing dynamics by applying a numerical calculation of the Bassetti-Erskine analytic solution to symplectic particle tracking codes. The numerical calculation is benchmarked against the analytic solution by calculating the luminosity reduction for several colliding beam scenarios. Benchmarking results show good agreement be-tween the numerical calculation and analytic solution, paving the way for implementation of the beam-beam kick to Elegant tracking simulations.
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MOPML006	Multi-Stage Electron Cooling Scheme for JLEIC	emittance, proton, electron, collider	397
	H. Zhang, S.V. Benson, Y.S. Derbenev, Y. Roblin, Y. Zhang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357. JLEIC is the future electron ion collider under design at Jefferson Lab, which will provide a luminosity up to 10³⁴ cm^-2s^-1. Electron cooling is essential for JLEIC to overcome the intrabeam scattering effect, reduce the ion beam emittance and thus achieve the high luminosity. The cooling time is approximately in proportion to the square of the energy and the 6D emittance. To avoid the difficulty of cooling the ion beam with large emittance at high energy, a multi-stage cooing scheme was designed for JLEIC. The ion beam was cooled at the low energy to reduce the emittance. Then it was ramped up to the collision energy. During the collision, electron cooling is implemented to maintain the emittance and the luminosity. Simulations for proton beam and lead ion beam at various stages are presented in this paper.
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MOPML010	Challenges and Status of Tuning Simulations for CLIC Traditional Beam Delivery System	luminosity, linear-collider, collider, lattice	412
	R.M. Bodenstein, P. Burrows JAI, Oxford, United Kingdom E. Marín CERN, Geneva, Switzerland
	The beam delivery system (BDS) for the 3 TeV version of the Compact Linear Collider (CLIC) has two main design types. One type is referred to as the local scheme, as it is approximately one kilometer shorter and corrects the chromaticity in both planes. The other type is referred to as the traditional scheme, and separates the chromaticity correction of each plane into different areas. The expectation early in the studies was that the traditional scheme would be easier to tune. This work will address the problems experienced in tuning simulations for the traditional BDS and describe the current state of these simulations.
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MOPML012	Special Collimation System Configuration for the LHC High-Beta Runs	background, collimation, detector, experiment	418
	H. Garcia Morales Royal Holloway, University of London, Surrey, United Kingdom R. Bruce, H. Burkhardt, M. Deile, S. Jakobsen, A. Mereghetti, S. Redaelli CERN, Geneva, Switzerland
	Special LHC high-beta optics is required for the forward physics program of TOTEM and ATLAS-ALFA. In this configuration, the beam is de-squeezed (the \beta-function at the collision point is increased) in order to minimize the divergence for measurements at very small scattering angles. In these low beam intensity runs, it is important to place the Roman Pots (RPs) as close as possible to the beam, which demands special collimator settings. During Run I, a significant amount of background was observed in the forward detectors due to particles outscattered from the primary collimator. During Run II, a different collimation configuration was used where a tungsten collimator was used as primary collimator instead of the usual one made of carbon. Using this configuration, a significant reduction of the background at the RPs was observed. In this paper we present a description of the new collimator configuration and the results obtained during the high-beta run carried out in 2016.
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MOPML020	Numerical Simulations to Evaluate and Compare the Performances of Existing and Novel Degrader Materials for Proton Therapy	scattering, emittance, proton, shielding	435
	R. Tesse, A. Dubus, N. Pauly ULB - FSA - SMN, Bruxelles, Belgium C. Hernalsteens, W.J.G.M. Kleeven, F. Stichelbaut IBA, Louvain-la-Neuve, Belgium
	The performance of the energy degrader in terms of beam properties directly impacts the design and cost of cyclotron-based proton therapy centers. The aim of this study is to evaluate the performances of different existing and novel degrader materials. The quantitative estimate is based on detailed Geant4 simulations that analyze the beam-matter interaction and provide a determination of the beam emittance increase and transmission. Comparisons between existing (aluminium, graphite, beryllium) and novel (boron carbide and diamond) degrader materials are provided and evaluated against semi-analytical models of multiple Coulomb scattering. The results showing a potential in emittance reduction for novel materials are presented and discussed in detail.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML020
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MOPML022	Development of Travelling Wave Accelerating Structure for a 10 MeV E-Linac	electron, bunching, radiation, linac	443
	J.H. Yang, Y. Yang CIAE, Beijing, People's Republic of China G. Han China Institute of Atomic Energy, Beijing, People's Republic of China
	Electron irradiation processing is a vital application field of nuclear technology application. China Institute of Atomic Energy (CIAE) developed several 10 MeV high power electron irradiating accelerator successfully, promoting the development of high energy high power irradiating accelerator technology and electron irradiation processing in China. The paper introduced the development of a 10 MeV travelling wave accelerating tube. The tube operates at 2856 MHz in 2π/3 mode. The SUPERFISH and PARMELA are used for the physical design. Several methods are used for microwave parameter measurement and tuning. The high power test shows the beam energy is 10.3 MeV and average beam power is 24.3 kW.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML022
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MOPML023	Very-High Energy Electron (VHEE) Studies at CERN's CLEAR User Facility	experiment, electron, scattering, proton	445
	A. Lagzda, R.M. Jones UMAN, Manchester, United Kingdom A. Aitkenhead, K. Kirkby, R. MacKay, M. Van Herk The Christie NHS Foundation Trust, Manchester, United Kingdom R. Corsini, W. Farabolini CERN, Geneva, Switzerland
	Funding: Science and Technology Facilities Council (STFC) - United Kingdom Here we investigate how inserts of various densities (0.001-2.2 g/cm³) affect the dose distribution properties of VHEE beams at ~150 MeV. A range variation comparison was also made with clinical proton beams using TOPAS/GEANT4 Monte Carlo simulations. In addition, we assess the viability of scattering foils for optimizing the size of VHEE beams for radiotherapy purposes. The experiments were conducted at CERN's CLEAR user facility.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPML023
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MOPML039	Comparison of Two Types of Steerers Applied in Proton Therapy Gantry	quadrupole, proton, superconductivity, radiation	488
	Z.F. Zhao, Q.S. Chen, S. Hu, X. Liu, B. Qin, W. Wei HUST, Wuhan, People's Republic of China W. Chen Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
	A proton therapy project HUST-PTF (HUST Proton Therapy Facility) based on a 250MeV isochronous superconducting cyclotron is under development in Huazhong University of Science and Technology (HUST). Based on the optics design of the gantry, the steering magnets need to be placed in a compact structure, as well as meet the magnetic field requirement with a maximum deflection angle of ±5mrad@250MeV. In the paper, two types of steerers (O-shape and H-shape) were introduced and discussed in detail. The magnetic fringe field interference effects between quadrupoles and steerers were studied by using OPERA/TOSCA code. The result based on the contrastive analysis will give us a valuable reference to choose suitable steerers for proton therapy beamline.
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MOPML052	The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators	cavity, electron, linac, impedance	520
	D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick LANL, Los Alamos, New Mexico, USA V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi SLAC, Menlo Park, California, USA
	Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515. Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities *. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype. See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf ** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03
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MOPML054	Production and Collection of He-3 and Other Valuable Isotopes using Mu*STAR	controls, proton, MMI, interface	527
	R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts Muons, Inc, Illinois, USA
	We propose an example facility based on GEM*STAR, an accelerator-driven molten-salt-fueled graphite-moderated thermal-spectrum reactor that can operate with different fissile fuels and uses a LiF-BeF2 molten eutectic carrier salt. In the first example, they propose using the 6Li in the LiF carrier to produce more than 2 kg/y of tritium (decaying to 3He with 12.3 year half-life) using a 2.5 MWb superconducting proton linac to drive the subcritical 500 MWt reactor burning surplus plutonium. The collection of other valuable fission-product radioisotopes like 133Xe will also benefit from the high temperature and continuous removal and separation afforded by fractional distillation
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MOPML055	Preliminary Physics Design of a Linac with the Variable Energy for Industrial Applications	linac, electron, gun, beam-loading	530
	Zh. X. Tang USTC, Hefei, Anhui, People's Republic of China L. Wang, D.R. Xu USTC/NSRL, Hefei, Anhui, People's Republic of China
	This paper describes the physics design of a S-band (2856 MHz) linear accelerator (linac) with variable energy tuning. The system consists of a DC gun for generating electron, prebuncher for velocity modulation and two travelling wave (TW) accelerating sections for acceleration. The accelerating structure is a 2'Ð/3 mode constant gradient TW structure, which comprises TW buncher cells, followed by uniform cells. The structure is designed to accelerate 45 keV electron beam from the electron gun to 3.2 MeV, and then 10 MeV. An important feature of the TW linac is that the RF output power of the first linac is as the RF input power of the second linac. Three dimensional transient simulations of the accelerating structure along with the input and output couplers have been performed to explicitly demonstrate this feature. Beam dynamics is performed to calculate the beam parameter.
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MOPML060	Self-Consistent Simulation and Optimization of Space-Charge Limited Thermionic Energy Converters	electron, space-charge, cathode, feedback	543
	N.M. Cook, J.P. Edelen, C.C. Hall RadiaSoft LLC, Boulder, Colorado, USA J.-L. Vay LBNL, Berkeley, California, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0017162. Thermionic energy converters (TEC) are an attractive technology for modular, efficient transfer of heat to electrical energy. The steady-state dynamics of a TEC are a function of the emission characteristics of the cathode and anode, an array of intra-gap electrodes and dielectric structures, and the self-consistent dynamics of the electrons in the gap. Proper modeling of these devices requires self-consistent simulation of the electron interactions in the gap. We present results from simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We consider the role of individual energy loss mechanisms in reducing device efficiency, including kinetic losses, radiative losses, and dielectric charging. We discuss the implementation of an external circuit model to provide realistic feedback. Lastly, we illustrate the potential to use nonlinear optimization to maximize the efficiency of these devices by examining grid transparency.
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MOPML061	Hadron Therapy Machine Simulations Using BDSIM	hadron, hadrontherapy, lattice, proton	546
	W. Shields JAI, Egham, Surrey, United Kingdom S.T. Boogert, L.J. Nevay Royal Holloway, University of London, Surrey, United Kingdom J. Snuverink PSI, Villigen PSI, Switzerland
	Minimising the background radiation dose in hadron therapy from particle losses and secondary emissions is of the highest importance for patient protection. To achieve this, tracking particles from source to the patient delivery region in a single simulation provides a quantitative description that distinguishes the background radiation from the treatment dose arriving at the gantry's isocentre. We demonstrate the ability to simulate beam transport, particle loss studies, and background radiation tracking in an example hadron therapy machine using BDSIM, a Geant4 based Monte Carlo simulation code for tracking high energy particles within a particle accelerator and its surrounding environment. Machine optics verification is also demonstrated through comparison to existing accelerator tracking codes.
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MOPML069	Enhancing Hadron Therapy through OMA	proton, FEL, medical-accelerators, hadron	568
	C.P. Welsch The University of Liverpool, Liverpool, United Kingdom C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie SkłodowskaCurie grant agreement No 675265. Continued research into the optimization of medical accelerators is urgently required to assure the best possible cancer care for patients and this is one of the central aims of the OMA project which received 4 M€ of funding from the European Commission. A consortium of universities, research and clinical facilities, as well as partners from industry carry out an interdisciplinary R&D program across three closely interlinked scientific work packages. These address the development of novel beam imaging and diagnostics systems, studies into treatment optimization including innovative schemes for beam delivery and enhanced biological and physical models in Monte Carlo codes, as well as R&D into clinical facility design and optimization to ensure optimum patient treatment along with maximum efficiency. Selected research highlights from across these work packages will be presented and the impact on hadron therapy facilities around the world discussed.
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MOPML070	Thermal and Stress Analysis of an X-Ray Target for 6 MeV Medical Linear Accelerators	target, electron, site, photon	572
	Z.H. Wang, H.B. Chen, J. Shi, H. Zha TUB, Beijing, People's Republic of China
	We present an optimal design of an X-ray target for 6 MeV medical linear accelerators using FLUKA simula-tions. The target is composed of high-atomic number tungsten and high-thermal conductivity copper, corre-sponding water-cooling system is showed too. Further-more, we analyse the temperature and thermal stress re-sponses of the target under transient thermal loads using Ansys Code. For 6 MeV electron beam with 100 uA cur-rent, the results show that the target can achieve 1014 cGy/min at 1meter in front of the target. Within 100 ms, the maximum temperature reaches 512 °C under pulsed heating source with 250 Hz frequency and 1' duty cycle and the number of cycles to failure is estimated as 5.8·10⁸.
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TUXGBF3	Reduction of the Kicker Impedance Maintaining the Performance of Present Kicker Magnet at RCS in J-PARC	kicker, impedance, synchrotron, extraction	616
	Y. Shobuda, Y. Irie, T. Takayanagi, T. Togashi, K. Yamamoto, M. Yamamoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The present kicker at RCS in J-PARC is designed to make a waveform by superposing the forward and backward currents from the power source to extract beams, so that one terminal of the kicker is shorted and the other one is open. On the other hand, the kicker impedance is the dominant source of the beam instability at the RCS. This report proposes a scheme to reduce the kicker impedance, maintaining the beneficial of the superposition of currents with the present kicker magnet.
	Slides TUXGBF3 [9.947 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF3
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TUXGBF4	ORBIT Simulation, Measurement and Mitigation of Transverse Beam Instability in the Presence of Strong Space Charge in the 3-GeV RCS of J-PARC	impedance, injection, acceleration, space-charge	620
	P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The transverse impedance of eight extraction pulse kicker magnets (KM) is extremely strong source of transverse beam instability in the 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC. To realize the designed 1 MW beam power, collective beam dynamics with including the space charge effect for the coupled bunch instabilities excited by the KM impedance and associated measures were studied by incorporating all realistic time-dependent machine parameters in the ORBIT 3-D particle tracking code. The simulation results were all reproduced by measurements and, as a consequence, an acceleration of 1 MW beam power has been successfully demonstrated. In order to maintain variation of the RCS parameters required for multi-user operation, realistic measures for beam instability mitigation were proposed and also been successfully implemented in reality. To further increase the RCS beam power, beam stability issues and possible measures beyond 1 MW beam power are also considered.
	Slides TUXGBF4 [2.241 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBF4
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TUYGBD4	Beam Loss Background and Collimator Design in CEPC Double Ring	detector, scattering, background, radiation	632
	S. Bai, J. Gao, H. Geng, D. Wang, Y. Wang, C.H. Yu, Y. Zhang IHEP, Beijing, People's Republic of China
	The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Radiative Bhabha scattering and Beamstrahlung effects are dominant mechanism of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam loss background in simulation and designed a series of collimators to suppress the radiation level on the machine and the detector.
	Slides TUYGBD4 [0.791 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUYGBD4
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TUPAF005	Status of AC-Dipole Project at RHIC Injectors for Polarized Helions	dipole, booster, resonance, proton	669
	K. Hock, H. Huang, F. Méot, P. Oddo, N. Tsoupas, J.E. Tuozzolo, K. Zeno BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Polarized helions will be used in the eRHIC collider to collide with polarized electrons. To allow efficient transport of polarized helions in the Booster, to rigidities sufficiently high (B rho=10.8 T.m, \|G gamma\|=10.5) for minimizing the optical perturbations from the two partial helical dipoles in the AGS, an upgrade for overcoming depolarizing intrinsic resonances is needed. An AC-dipole is being designed to induce spin flips through intrinsic resonances. Booster AC-dipole operation will be established with protons while the polarized helion source is being completed. This paper reports the status of the project (which is now well advanced after two years of theoretical and design studies) and provides an overview of proof of principle experiments to take place after successful installation of the AC-dipole, during RHIC Run 19 with polarized proton beams.
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TUPAF025	Multi-turn Study in FLUKA for the Design of CERN-PS Internal Beam Dumps	dumping, experiment, operation, proton	724
	J.A. Briz Monago, M. Calviani, F. Cerutti, J.J. Esala, S.S. Gilardoni, F.-X. Nuiry, G. Romagnoli, G. Sterbini, V. Vlachoudis CERN, Geneva, Switzerland
	The CERN Proton-Synchrotron (PS) accelerator is currently equipped with two internal beam dumps in operation since the 1970's. An upgrade is required to be able to withstand the beams that will be produced after the end of the LIU (LHC Injector Upgrade) project. For the design of the new dumps, the interaction and transport of beam and all secondary particles generated has been simulated using FLUKA. The working principle of the internal beam dump in the PS ring is very peculiar with respect to the other dumps in the CERN accelerator complex. A moving dump intercepts the circulating beam during few milliseconds like a fast scraper. The moving dump shaving the beam, the multi-turn transport of beam particles in the PS accelerator and a time-dependent energy deposition in the dump were modeled. The methodology and the results obtained in our studies for the dump core and downstream equipment will be reported in this contribution.
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TUPAF027	CERN PS Kicker for Proton Injection: from Beam-Based Waveform Measurements to Hardware Improvements	kicker, injection, emittance, flattop	732
	V. Forte, A. Ferrero Colomo, M.A. Fraser, T. Kramer CERN, Geneva, Switzerland
	For 2017 operation, the termination mode of the CERN Proton Synchrotron (PS) horizontal injection kicker was permanently changed to short-circuited, to be compliant with the future performances requested by the LHC Injectors Upgrade (LIU) project. An extensive campaign of measurements was performed through a dedicated beam-based technique. The measurements identified possibilities for optimisation of the kicker system and were fundamental to properly tune the PSpice simulation model of the kicker, as well as for validating the hardware changes. The model was finally used to estimate the horizontal emittance growth for the future injection schemes in the PS.
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TUPAF028	Energy Deposition Studies and Analysis of the Quench Behavior in the Case of Asynchronous Dumps During 6.5 TeV LHC Proton Beam Operation	superconducting-magnet, proton, quadrupole, kicker	736
	M.I. Frankl, W. Bartmann, M. Bednarek, C. Bracco, A. Lechner, A.P. Verweij, C. Wiesner, D. Wollmann CERN, Geneva, Switzerland
	The CERN LHC beam dumping system comprises a series of septa and fast-pulsed kicker magnets for extracting the stored proton beams to the external beam dumps. Different absorbers in the extraction region protect superconducting magnets and other machine elements in case of abnormal beam aborts, where bunches are swept across the machine aperture. During Run 2 of the LHC, controlled beam loss experiments were carried out at 6.5 TeV probing the particle leakage from protection devices under realistic operation conditions. This paper presents particle shower simulations analyzing the energy deposition in superconducting coils and assessing if the observed magnet quenches are compatible with the presently known quench limits.
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TUPAF030	Electron Cloud Build Up for LHC Sawtooth Vacuum Chamber	electron, vacuum, photon, synchrotron	744
	G. Guillermo Cantón, F. Zimmermann CERN, Geneva, Switzerland G.H.I. Maury Cuna, E. D. Ocampo Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
	At high proton-beam energies, beam-induced synchrotron radiation is an important source of heating, of beam-related vacuum pressure increase, and of primary photoelectrons, which can give rise to an electron cloud. For the arcs of LHC a sawtooth pattern had been imprinted on the horizontally outward side of the vacuum chamber in order to locally absorb synchrotron radiation photons without dispersing them all around the chamber. Using the combination of the codes Synrad3D and PyCLOUD we examine the effect of realistic absorption distributions with and without sawtooth on the build up of electron clouds.
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TUPAF031	Beam Simulation Studies for the Upgrade of the SPS Beam Dumping System	kicker, dumping, operation, injection	747
	C. Heßler, W. Bartmann, E. Carlier, L. Ducimetière, B. Goddard, F.M. Velotti CERN, Geneva, Switzerland
	The SPS at CERN currently uses a beam dumping system that is installed in the long straight section 1 (LSS1) of the SPS. This system consists of two beam stopper blocks for low and high energy beams, as well as two vertical and three horizontal kicker magnets, which deflect and dilute the beam on the dumps. Within the frame of the LHC injector upgrade project (LIU) the beam dumping system will be relocated to long straight section 5 (LSS5) and upgraded with an additional vertical kicker, new main switches and a single new beam dump, which covers the full energy range. The impact of a possible increase of the vertical kicker rise time on the beam has been studied in simulations with MAD-X for the different optics in the SPS. Furthermore, the impact on the beam in failure scenarios such as the non-firing of one kicker has been investigated. The results of these studies will be presented and discussed in this paper. Operational mitigation methods to deal with an increased rise time will also be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF031
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TUPAF035	Observations of SPS Slow-Extracted Spill Quality Degradation and Possible Improvements	extraction, quadrupole, power-supply, experiment	761
	F.M. Velotti, H. Bartosik, K. Cornelis, M.A. Fraser, B. Goddard, S. Hirlaender, V. Kain, O. Michels, M. Pari CERN, Geneva, Switzerland
	The SPS delivers slow extracted proton and heavy ion spills of several seconds to the North Area fixed target experiments with a very high duty factor. Reduced machine reproducibility due to magnetic history and power supply ripples on the main circuits lead however to frequent degradation of the spill duty factor. In this paper, the measured effect of the SPS magnetic history on spill quality and principal machine parameters is presented. Another detailed measurement campaign was aimed at characterising the frequency content and response of the spill to noise on the main power supplies ripples. The main findings of this study will also be reported. Finally, simulations of possible improvements based on the data acquired are discussed, as well as an extrapolation to the possible spill quality after the implementation of the improvements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF035
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TUPAF037	Validation of the CERN PS Eddy Current Injection Septa	septum, vacuum, injection, HOM	768
	M. Hourican, B. Balhan, J.C.C.M. Borburgh, T. Masson, A. Sanz Ull CERN, Geneva, Switzerland
	As part of the upgrade of the CERN PS accelerator from 1.4 GeV to 2 GeV, new injection septa have been developed. The system is comprised of a pulsed eddy current septum magnet and a pulsed eddy current bumper magnet. Both magnets will be housed in a common vacuum vessel and powered by independent power converters. In-depth studies and simulations have been performed to reduce as much as possible the leak field by designing specific magnetic shielding, combined with dual function beam impedance shielding. A prototype magnet was built and measured to validate the simulations. The final complete system will be bake-able at 200C and uses demineralised water for cooling. Closed circuit cooling systems have been integrated to reduce risks of vacuum leaks. This report describes the electromechanical design from the concept and simulation stages to the prototyping and final manufacturing. Results of the initial magnetic measurements, including field homogeneity and leak field mitigation methods are presented.
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TUPAF039	Electron Cooling Simulation and Experimental Benchmarks at LEIR	electron, plasma, experiment, solenoid	776
	A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer CERN, Geneva, Switzerland
	A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF039
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TUPAF040	Beam Loss Measurements for Recurring Fast Loss Events During 2017 LHC Operation Possibly Caused by Macroparticles	proton, operation, dipole, insertion	780
	A. Lechner, B. Auchmann, E. Bravin, A.A. Gorzawski, L. K. Grob, E.B. Holzer, B. Lindstrom, T. Medvedeva, D. Mirarchi, R. Schmidt, M. Valette, D. Wollmann CERN, Geneva, Switzerland
	The availability of the LHC machine was adversely affected in 2017 by tens of beam aborts provoked by frequent loss events in one standard arc cell (16L2). In most of the cases, the dumps were triggered by concurrently developing fast beam instabilities leading to particle losses in the betatron cleaning insertion. Many of the events started with a distinct sub-millisecond loss peak comparable to regular dust particle events, which have been observed along all the LHC since the start-up. In contrast to regular dust events, persistent losses developed in cell 16L2 after the initial peaks which can possibly be explained by a phase transition of macroparticles to the gas phase. In this paper, we summarize the observed loss characteristics such as spatial loss pattern and time profiles measured by Beam Loss Monitors (ionization chambers). Based on the measurements, we estimate the energy deposition in macroparticles and reconstruct proton loss rates as well as the gas densities after the phase transition. Differences between regular dust events and events in 16L2 are highlighted and the ability to induce magnet quenches is discussed.
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TUPAF046	Conceptual Design of a Collimation System for the CERN Super Proton Synchrotron	collimation, optics, proton, injection	802
	M. Patecki, A. Mereghetti, D. Mirarchi, S. Redaelli CERN, Geneva, Switzerland
	The Super Proton Synchrotron (SPS) is the last accelerator in the LHC Injectors Chain. Its performance is constantly being improved in frame of the LHC Injectors Upgrade (LIU) Project in order to prepare it for the future HL-LHC (High Luminosity LHC) operation. One of the LIU goals is to nearly double the intensity extracted from the SPS, up to 2.32×10¹¹ p/bunch. In recent years, nearly 10% of losses are observed for nominal intensity and LHC-type beams; they grow to about 20% for the intensity approaching the HL-LHC target. Beam losses imply activation and aging of the SPS hardware; the possibility to add a collimation system is being considered to mitigate this problem. In this paper we present studies of a collimation system design for the SPS. The concept is based on a primary horizontal collimator located in an available position with high enough dispersion, and a secondary collimator to intercept the particles leaking out from the primary collimator. Performance of the proposed collimation system is evaluated by means of numerical simulations.
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TUPAF048	LIU Space Charge Studies for the LHC Pre-Accelerators	space-charge, injection, proton, resonance	810
	F. Schmidt, H. Bartosik CERN, Geneva, Switzerland
	In 2011 a working group has been started to study performance limitations due to Space Charge (SC) in the four LHC pre-accelerators, LEIR, PSB, PS & SPS, in view of the LHC Injector Upgrade (LIU) project. To this end external and in-house simulation tools have been benchmarked for the LIU study cases with the long-term goal of providing a full sequence of tested CERN Space Charge tools. It became clear that SC studies must be combined with trustworthy models of the machines, including linear and non-linear errors. In particular an effective s-dependent non-linear model is required. Recent studies indicate that also the low frequency ripple spectrum due to conventional power supplies might play an important role for the beam dynamics in presence of space charge in the pre-injectors.
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TUPAF051	Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS	extraction, octupole, multipole, optics	822
	L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard CERN, Geneva, Switzerland K.A. Brown BNL, Upton, Long Island, New York, USA
	Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed.
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TUPAF052	Effects of Electrostatic Septum Alignment on Particle Loss During Slow Extraction at CERN SPS	alignment, extraction, operation, septum	826
	J. Prieto, Y. Dutheil, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti CERN, Geneva, Switzerland M.A. Kagan SLAC, Menlo Park, California, USA
	Slow extraction is an intrinsically lossy process that splits the beam with an electrostatic septum (ES), employing a thin-wire array to delimit the high electric field region that deflects the beam into the extraction channel. At CERN's Super Proton Synchrotron (SPS) the ES is over 16 m long and composed of 5 separate units containing separate wire-arrays that can be moved independently. The tanks are all mounted on a single support structure that can move the ensemble coherently. As a result, the large number of positional degrees of freedom complicates the alignment procedure in operation. Obtaining and maintaining accurate alignment of the ES with the beam is therefore crucial for minimising beam loss. In this paper, we investigate the alignment procedure for different operational scenarios using particle tracking simulations to understand the beam loss along the extraction straight as a function of the relative positions of each of the 5 separate ES units. An important aspect of the study was to understand the required alignment tolerance to achieve optimum extraction efficiency for a given configuration of wire-array thicknesses.
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TUPAF053	Optimization of Diffuser (Pre-Scatterer) Configurations for Slow Extraction Loss Reduction at Electrostatic Septa	septum, scattering, extraction, proton	830
	B. Goddard, B. Balhan, J.C.C.M. Borburgh, M.A. Fraser, L.O. Jorat, V. Kain, C. Lolliot, L.S. Stoel, P. Van Trappen, F.M. Velotti CERN, Geneva, Switzerland D. Barna Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary V.P. Nagaslaev Fermilab, Batavia, Illinois, USA
	Uncontrolled beam loss at the electrostatic septum is a performance limit for several existing or planned high power hadron accelerators delivering slow-extracted spills to fixed targets. A passive diffuser, or pre-scatterer, in a suitable configuration has been shown to reduce such beamloss significantly, with the actual gain factor depending on the parameters and details of the extraction process and hardware. In this paper, the optimization of diffuser configurations is investigated for a range of beam energies and extraction conditions, and the sensitivity to the available parameters explored via simulation results. The advantages and limitations of the diffuser are discussed and conclusions drawn concerning the specific case studies of the 8 GeV Fermilab debuncher ring and 400 GeV CERN SPS.
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TUPAF054	Slow Extraction Efficiency Measurements at the CERN SPS	extraction, proton, operation, septum	834
	M.A. Fraser, K. Cornelis, L.S. Esposito, B. Goddard, V. Kain, F. Roncarolo, L.S. Stoel, F.M. Velotti CERN, Geneva, Switzerland
	The high efficiency of most slow extraction systems makes quantifying the exact amount of beam lost in the process extremely challenging. This is compounded by the lack of time structure in the extracted beam, as is typically required by the high-energy physics experiments, and the difficulty in accurately calibrating D.C. intensity monitors in the extraction line at count rates of ~ 10¹³ Hz. As a result, it is common for the extraction inefficiency to be measured by calibrating the beam loss signal induced by the slow extraction process itself. In this paper, measurements of the extraction efficiency performed at the CERN Super Proton Synchrotron for the third-integer resonant slow extraction of 400 GeV protons over recent years will be presented and compared to expectation from simulation. The technique employed will be discussed along with its limitations and an outlook towards a future online extraction efficiency monitoring system will be given.
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TUPAF055	Progress Toward a Dynamic Extraction Bump for Slow Extraction in the CERN SPS	extraction, alignment, septum, closed-orbit	838
	L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard, J. Prieto, F.M. Velotti CERN, Geneva, Switzerland
	The possibility of reducing the angular spread of slow extracted particles with a time-dependent extraction bump at the CERN Super Proton Synchrotron (SPS) is under investigation. In order to create this so-called dynamic bump, two orthogonal knobs were designed to enable independent movements of the beam in position and angle at the upstream end of the electrostatic extraction septum (ES). With the present slow extraction scheme, simulations show that the use of a dynamic bump can reduce the angular spread at the ES by roughly a factor two and reduce beam loss on the ES. A reduction in the angular spread is also a prerequisite to exploit the full potential of other loss reduction techniques being considered for implementation at the SPS, like the active or passive diffusers planned for installation upstream of the ES in 2018. In this paper, the simulated loss reduction with a dynamic bump alone or in combination with other loss reduction techniques will be assessed, the first beam-based tests of the dynamic bump presented, the details of its implementation examined and its potential for future operation at the SPS discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF055
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TUPAF061	Use of a Massless Septum to Increase Slow-Extraction Efficiency	septum, extraction, sextupole, resonance	862
	K. Brunner, M.A. Fraser, B. Goddard, L.S. Stoel, C. Wiesner CERN, Geneva, Switzerland D. Barna Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
	The Super Proton Synchrotron (SPS) at CERN provides slow-extracted beam for Fixed Target experiments in the North Area. For the higher extracted beam intensities requested by future experimental proposals, beam-loss induced activation will be one of the limiting factors for the availability of such a facility. In this paper, we present and discuss the concept of using a massless septum magnet to increase the extraction efficiency and decrease losses caused by protons scattering on the electrostatic-septa wires.
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TUPAF066	Transverse Dynamics and Software Integration of the ESS Low Energy Beam Transport	solenoid, MMI, ion-source, proton	882
	N. Milas, K.S. Louisy, D.C. Plostinar ESS, Lund, Sweden
	The first part of the ESS linac, also called front-end, comprising the Ion Source and the Low Energy Beam Transport (LEBT) section, will be installed and commissioned in 2018. The LEBT is used to focus and correct the proton beam trajectory and clean the head and tail of the proton pulse from the flat top before entering the RFQ. During the ion source and LEBT commissioning a full beam characterization at the RFQ entrance interface is planned. It is thus important to have an application in the control room able to display quantities measured by the diagnostic devices and also to quickly run a simulation including not only centre of mass dynamics but also envelope. This paper presents the efforts in modelling the LEBT elements, as accurately as possible, and implementing the dynamics calculation and integration with diagnostics tools. The final result is a Java FX GUI based on the OpenXAL library.
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TUPAF073	Simulation of Integrable Synchrotron with Space-charge and Chromatic Tune-shifts	lattice, space-charge, optics, synchrotron	894
	J.S. Eldred, A. Valishev Fermilab, Batavia, Illinois, USA
	We present a nonlinear rapid-cycling synchrotron designed as a high-intensity replacement of the Fermilab Booster. The design incorporates integrable optics, an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use the Synergia space-charge tracking code to demonstrate the stability of a beam in this lattice with a space-charge tune-shift up to 0.4 and a rms momentum spread up to 0.4\%. We demonstrate the benefit of increased lattice periodicity.
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TUPAF079	Scaled Alvarez-Cavity Model Investigations for the UNILAC Upgrade	DTL, cavity, alignment, pick-up	916
	M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, M. Vossberg GSI, Darmstadt, Germany A. Seibel IAP, Frankfurt am Main, Germany
	The 1:3 scaled aluminum model of an Alvarez-type cavity with 10 gaps was used for comparison of simulation with measurement for the frequency and the electric field on axis. The scaled frequency is 325.224 MHz and an Alvarez cavity has a small frequency tuning range. With this scaled model it was possible to apply different stem configurations for each drift tube to damp parasitic modes and to increase the field stability. The new drift tubes have an optimized free-formed profile on the end plates in order to increase the shunt impedance. In special the assembly, positioning and alignment of the drift tubes can be tested and the frequency change can be investigated in this respect.
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TUPAF080	Final Design of the FoS Alvarez-Cavity-Section for the Upgraded UNILAC	cavity, DTL, quadrupole, operation	920
	M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, C. Mühle, A. Rubin, V. Srinivasan GSI, Darmstadt, Germany A. Seibel IAP, Frankfurt am Main, Germany
	The final design describes the First-of-Series (FoS) Alvarez-Cavity-section of the first tank being part of the new post-stripper DTL of the UNILAC. The FoS-cavity has an input energy of 1.358 MeV/u with 11 drift tubes (including quadrupole singlets) in a total length of 1.9 m and a diameter of 2 m with an operation frequency of 10⁸.4 MHz. The drift tubes will have a new shape profile at the end plates. The single layered quadruple singlets inside the drift tubes are pulsed with 10 Hz and will have a maximum field gradient of 51 T/m. The new drift tube design combines the new shape profile with the transverse and longitudinal installation space of the magnet. The FoS Alvarez-cavity will be part of the first section of the new Alvarez DTL. It shall be operated at nominal RF- and magnetic fields prior to procurement of the series.
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TUPAF086	Adaption of the HSI -RFQ Rf-Properties to an Improved Beam Dynamics Layout	rfq, operation, linac, resonance	938
	M. Vossberg, L. Groening, S. Mickat, H. Vormann, C. Xiao GSI, Darmstadt, Germany V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi CERN, Geneva, Switzerland
	The GSI accelerator facility comprising the linear accelerator UNILAC and the synchrotron SIS18 will be used in future mainly as the injector for the Facility for Anti-Proton and Ion Research (FAIR) being under construction. FAIR requires high beam brilliance and the UNILAC's RFQ electrodes must be upgraded with respect to their beam dynamics design. The new layout is currently being conducted at CERN with the aim of adjusting the electrode voltage according to the design voltage of 123 kV. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. Simulations on the frequency dependence of the rings shapes and their impact on the voltage distribution along the RFQ are presented.
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TUPAF087	A Two-Stage Splitring-RFQ for High Current Ion Beams at Low Frequencies	rfq, impedance, acceleration, resonance	941
	M. Baschke, H. Podlech, A. Schempp IAP, Frankfurt am Main, Germany
	Funding: HIC for FAIR, BMBF Contr. No. 05P15RFRBA For several accelerator projects RFQs are the first stage of acceleration. To reach high intensities a new Splitring-RFQ is investigated. Not only a high current and high beam quality/brilliance should be achieved, also a good tuning flexibility and comfort for maintenance are part of the study. The RFQ will consist of two stages with 27 MHz and 54 MHz to accelerate ions with an A/q of 60 up to energies of 200 keV/u. RF simulations with CST MWS have been performed to obtain the quality factor, shunt impedance and voltage distribution as well as tuning possibilities. The results and the status of the project will be presented.
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TUPAF089	Initial Measurements on a New 10⁸ MHz 4-Rod CW RFQ Prototype for the HLI at GSI	rfq, dipole, linac, resonance	946
	D. Koser, K. Kümpel, H. Podlech IAP, Frankfurt am Main, Germany P. Gerhard GSI, Darmstadt, Germany O.K. Kester TRIUMF, Vancouver, Canada
	Funding: Work supported by BMBF Contr. No. 05P15RFBA and HIC for FAIR The High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, is one of the two injector linacs for the Universal Linear Accelerator (UNILAC) and is also planned to serve as dedicated injector for a proposed superconducting CW linac for heavy element research. Within the scope of an intended CW upgrade of the HLI front end, a replacement for the existing 4-rod RFQ is desirable since its stable operation and performance is severely impeded by mechanical vibrations of the electrodes and a high thermal sensitivity. With the aim of suppressing mechanical vibrations and providing efficient cooling considering high power CW operation, a completely new and improved 4-rod design was developed* with a focus on structural mechanical simulations using ANSYS. In order to validate the simulated RF performance, thermal behavior and structural mechanical characteristics, a 6-stem prototype was manufactured**. Initial low power RF measurements and basic piezo actuated mechanical investigations were done and the anticipated properties could be confirmed prior to planned high power RF tests and further mechanical vibration studies. D. Koser et al., THPIK021, Proc. of IPAC2017 D. Koser et al., MOPOY020, Proc. of IPAC2016 * D. Koser et al., TUPLR057, Proc. of LINAC2016
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TUPAF090	Measurements of the MYRRHA-RFQ at the IAP Frankfurt	rfq, dipole, controls, resonance	949
	K. Kümpel, D. Koser, S. Lamprecht, N.F. Petry, H. Podlech, A. Schempp, D. Strecker IAP, Frankfurt am Main, Germany A. Bechtold NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany C. Zhang GSI, Darmstadt, Germany
	Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE) The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project is a planned accelerator driven system (ADS) which aims to demonstrate the feasibility of large scale transmutation. The first RF structure of the 600 MeV MYRRHA Linac will be a 176.1 MHz 4-Rod RFQ that will accelerate up to 4 mA protons in cw operation from 30 keV up to 1.5 MeV. The voltage along the approximately 4 m long electrodes has been chosen to 44 kV which limits the RF losses to about 25 kW/m. During the design of the structure a new method of dipole compensation has been applied. This paper describes the status of the RFQ and shows the results of the measurements done at IAP Frankfurt such as dipole and flatness measurement, vacuum tests and power tests up to 11 kW.
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TUPAK007	Simulation of Surface Muon Beamline, Ultra-Slow Muon Production and Extraction for the J-PARC g-2/EDM Experiment	target, experiment, laser, proton	970
	M. Otani, N. Kawamura, T. Mibe, T. Yamazaki KEK, Tsukuba, Japan K. Ishida RIKEN Nishina Center, Wako, Japan G. Marshall TRIUMF, Vancouver, Canada
	The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1 ppm to cast light on beyond standard model in elementary particle physics. The experiment utilizes a brand new muon beam line in J-PARC (H line), which is designed to have large acceptance to supply an intense muon beam. The surface muons are injected into a silica aerogel target to generate bound state of muon and electron (muonium). Then the muoniums are ionized by lasers and ultra slow (30 meV) muons (USM) are generated. The USM's are extracted by electro-static lens and injected to a muon linac. In this poster, simulation for optics of the surface muon beamline, muonium production and extraction by the electro-static lens, and the estimation of the USM's intensity are presented.
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TUPAK008	Longitudinal Bunch Size Measurements with an RF Deflector at J-PARC LINAC	radio-frequency, linac, rfq, DTL	974
	M. Otani, K. Futatsukawa KEK, Tsukuba, Japan K. Hirano, A. Miura JAEA/J-PARC, Tokai-mura, Japan Y. Liu KEK/JAEA, Ibaraki-Ken, Japan T. Maruta FRIB, East Lansing, USA
	Measurement of the longitudinal bunch size is important for the stable beam operation. Especially in a medium energy beam transport (MEBT) located after a radio-frequency quadrupole in J-PARC, it is necessary to measure the bunch size with minimum set of equipment to avoid subsequent emittance growth due to space charge. We had proposed a longitudinal size measurement with an rf deflector normally used for deflecting theμbunch; phase spread is migrated to spatial one if the reference particle arrives at the deflector when the voltage is rising in time and is zero. Then a buncher cavity located upstream of the deflector is utilized to scan the phase spread to measure the longitudinal beam parameters. In this poster, recent measurement results are presented.
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TUPAK009	Muon Profile Measurement After Acceleration With a Radio-Frequency Quadrupole Linac	experiment, rfq, linac, positron	977
	M. Otani, Y. Fukao, K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, T. Yamazaki KEK, Tsukuba, Japan S. Bae, H. Choi, S. Choi, B. Kim, H.S. Ko SNU, Seoul, Republic of Korea K. Hasegawa, Y. Kondo, T. Morishita JAEA/J-PARC, Tokai-mura, Japan T. Iijima, Y. Sue Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan H. Iinuma, Y. Nakazawa Ibaraki University, Ibaraki, Japan K. Ishida RIKEN Nishina Center, Wako, Japan R. Kitamura University of Tokyo, Tokyo, Japan S. Li The University of Tokyo, Graduate School of Science, Tokyo, Japan G.P. Razuvaev Budker INP & NSU, Novosibirsk, Russia N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan E. Won Korea University, Seoul, Republic of Korea
	Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784. The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1ppm. The experiment utilizes low emittance muon beam with a muon linac to sweep out beam related uncertainties, which limit the g-2 precision in past experiments. A beam matching with precise beam measurements is required to avoid substantial emittance growth and satisfy the experimental requirement on the beam emittance of around 1.5 pi mm mrad. We conduct profile measurement of muon after acceleration with a radio-frequency quadrupole (RFQ) on December 2017 following a first muon acceleration experiment on October. In the experiment of profile measurement, epi-thermal negative muonium ions are generated by injecting surface muons to a thin metal foil. The muonium ions are accelerated to 5 keV. by an electro-static lens and accelerated to 90 keV by the RFQ. Then the muonium ions are transported to a profile detector consisting of a micro-channel plate and a ccd camera via a quadrupole pair and a bending magnet. In this poster, the experimental result and comparison to the simulation are reported.
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TUPAK013	Geant4 Simulation of Radiation Effect on the Deflector of Extraction System in HUST SCC250	septum, proton, neutron, radiation	990
	S. Hu, K. Fan, L.X.F. Li, Z.Y. Mei, Z.J. Zeng, L.G. Zhang HUST, Wuhan, People's Republic of China
	China has payed extensive attention to the development of proton therapy in recent years. When design a compact, high energy superconducting cyclotron for proton therapy， radiation effect induced by beam losses is a crucial consideration. Since the proton beam is extracted out of HUST SCC250 by electrostatic deflectors, the fierce interaction between proton beam and the deflector septum is the main cause of beam losses, which will bring about radiation effect leading to activation and coil quench. This paper presents simulation results of radiation effect by utilizing Geant4 Monte Carlo code. The energy depositions of proton beam in various septum materials are compared. Meanwhile, the yields, the ener-gy and angular distributions of secondary particles are investigated. Those simulation results based on radiation effect will provide us with valuable implications for the design of this superconducting cyclotron.
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TUPAK017	Abandoned Proton Beam Separation Design at MOMENT	proton, target, separation-scheme, secondary-beams	1001
	C. Meng, H.T. Jing, Y.P. Song, J.Y. Tang, H. Wang IHEP, Beijing, People's Republic of China
	Funding: The National Natural Science Foundation of China under Grants 11575217 MOMENT (MuOn-decay MEdium baseline NeuTrino beam facility) is an accelerator-based neutrino beam facility using neutrino from muon decays. The proton driver is a continuous-wave proton linac of 1.5 GeV and 10 mA, which means an extremely high beam power of 15 MW. After bombarding the target, the abandoned proton beam power is very high and should be separate from target station carefully. Because of the energy is not very high and the layout of following transport line isn't linear, we should design special separation line for high momentum proton beam. In this paper the design of separation scheme at MOMENT will be proposed and discussed.
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TUPAL009	Studying a Prototype of Dual-beam Drift Tube Linac	DTL, cavity, rfq, acceleration	1020
	T. He, L. Lu, W. Ma, L.P. Sun, C.C. Xing, X.B. Xu, L. Yang IMP/CAS, Lanzhou, People's Republic of China
	For generating high-intensity ion beams from linear ac-celerators, a multi-beam acceleration method which in-volves multiple accelerating beams to suppress the defo-cusing force from space charge effects, then integrating these beams by a beam funneling system, has been pro-posed. An Inter-digital H-mode (IH) two-beam type radio frequency quadrupole (RFQ) with accelerating 108mA (54mA/channel×2) carbon ion from 5 to 60 keV/ u and an IH four-beam RFQ with accelerating 160.8mA (40.2mA/channel×4) carbon ion from 3.6 to 41.6 keV/u had been successfully designed for low energy heavy ion acceleration [1]. In order to demonstrate that an IH dual-beam drift tube linac (DB-DTL) is suitable for high-intensity heavy ion beam acceleration in middle energy region, we has been developing a DB-DTL prototype by using three dimensional electromagnetic CST MicroWave Studio (MWS) and using particles tracking Pi Mode Linac Orbit Calculation (PiMLOC) [2-3]. According to the simulation results, the beam dynamics design and elec-tromagnetic design will be presented in this paper. * Shota. Iketa et al., Nucl. Instr. and Meth. in Phys. Res. B.239-243 (2017).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL009
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TUPAL035	3D Beam Dynamics Modeling of MEBT for the New LANSCE RFQ Injector	emittance, rfq, quadrupole, proton	1081
	S.S. Kurennoy LANL, Los Alamos, New Mexico, USA
	The new RFQ-based proton injector at LANSCE requires a specialized medium-energy beam transfer (MEBT) after the RFQ at 750 keV due to a following long (~3 m) existing common transfer line that also serves for transporting negative-ion beams to the DTL entrance. The horizontal space for MEBT elements is limited because two beam lines merge at 18-degree angle. The MEBT design developed with envelope codes includes two compact quarter-wave RF bunchers and four short quadrupoles with steerers, all within the length of about 1 m. The beam size in the MEBT is large, comparable to the beam-pipe aperture, hence non-linear 3D field effects at large radii become important. Using CST Studio codes, we calculate buncher RF fields and quadrupole magnetic fields and use them to perform particle-in-cell beam dynamics modeling of MEBT with realistic beam distributions from the RFQ. Our results indicate a significant emittance growth not predicted by standard beam dynamics codes. Its origin was traced mainly to the quadrupole edge fields. Quadrupole design modifications are proposed to improve the MEBT performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL035
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TUPAL036	Slow Extraction Techniques at the Marburg Ion-Beam Therapy Centre	extraction, synchrotron, controls, resonance	1084
	C. Krantz, T. Fischer, Th. Haberer, B. Kroeck, U. Scheeler, A. Weber, M. Witt MIT, Marburg, Germany R. Cee, F. Faber, E. Feldmeier, M. Galonska, Th. Haberer, A. Peters, S. Scheloske, C. Schömers HIT, Heidelberg, Germany F. Faber Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany
	The Marburg Ion-Beam Therapy Centre offers hadron therapy using proton and carbon beams. The accelerator is based on a 65-m ion synchrotron by Danfysik/Siemens Healthcare. Beam extraction from the synchrotron is driven by a transverse RF knock-out (KO) system featuring Dynamic Intensity Control (DIC) of the spill. DIC allows modulation of the extraction rate by factors up to 30 on millisecond time scales. A fast response of the system to the variable intensity set-point can be obtained by careful adjustment of the RF-KO spectrum relative to the machine tune. Tracking simulations of the extraction phase have been conducted to refine that behaviour. Presently, we investigate how fast machine tune shifts, induced by an air-core quadrupole lens, can be used as a way to further improve the spill quality.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL036
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TUPAL043	Simulations of the Electron Column in IOTA	electron, plasma, proton, space-charge	1103
	B.T. Freemire Northern Illinois University, DeKalb, Illinois, USA S. Chattopadhyay Northern Illinois Univerity, DeKalb, Illinois, USA M. Chung UNIST, Ulsan, Republic of Korea C.S. Park Korea University Sejong Campus, Sejong, Republic of Korea G. Penn LBNL, Berkeley, California, USA V.D. Shiltsev, G. Stancari Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Contract Nos. DE-AC02-07CH11359 and DE-AC02-05CH1123 and General Accelerator Research and Development Program Future high current proton accelerators will need to minimize beam loss due to space-charge in order to achieve safe operation while achieving the desired physics goals. One method of space-charge compensation to be tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab is the Electron Column. The concept for this device is to allow a circulating beam to ionize a small region of relatively high pressure residual gas, while using electric and magnetic fields to confine and shape the resulting plasma electrons. If the profile of the electrons is matched to the beam profile transversely and longitudinally, the electrons should counteract the space-charge force of the proton beam. Simulations of the IOTA proton beam circulating through the Electron Column have been performed, with the evolution of the electron plasma and its effect on the beam studied.
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TUPAL056	High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron	closed-orbit, resonance, space-charge, vacuum	1140
	B.G. Pine, C.M. Warsop STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the spallation neutron source at Rutherford Appleton Laboratory in the UK. Protons are accelerated from 70 to 800 MeV in a 50 Hz rapid cycling synchrotron. Due to the intense beam, space charge forces are high during the first part of the acceleration cycle. The vacuum vessel in the synchrotron has a rectangular shape where the apertures are conformal to the design beam envelopes. At high intensities image forces interact with the beam, especially when the closed orbit is large. An analysis of image forces has been made and used to classify higher order image terms. These have been identified using simulations of round beams in rectangular vacuum vessels. The higher order image terms from harmonic closed orbits have been used with single particle resonance theory, taking account of the coherent nature of the beam response. Several predictions of beam resonance have been made. A simulation study has been carried out using a smooth focusing lattice and uniform density beams. Resonant beam behaviour has been observed and explained by the proposed theory.
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TUPAL058	Studies for Major ISIS Upgrades via Conventional RCS and Accumulator Ring Designs	injection, lattice, space-charge, emittance	1148
	C.M. Warsop, D.J. Adams, H.V. Cavanagh, P.T. Griffin-Hicks, B. Jones, B.G. Pine, R.E. Williamson STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
	ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK, which provides 0.2 MW of beam power via a 50 Hz, 800 MeV proton RCS. Detailed studies are now under way to find the optimal configuration for a next generation, short pulsed neutron source that will define a major ISIS upgrade in ~2031. Accelerator configurations being considered for the MW beam powers required include designs exploiting FFAG rings as well as conventional accumulator and synchrotron rings. This paper describes work exploring the latter, conventional options, but includes the possibility of pushing further toward intensity limits to reduce facility costs. The scope of planned studies is summarised, looking at optimal exploitation of existing ISIS infrastructure, and incorporating results from recent target studies and user consultations. Results from initial baseline studies for an accumulator ring and RCS located in the existing ISIS synchrotron hall are presented. Injection scheme, foil limits, longitudinal and transverse beam dynamics optimization with related beam loss and activation are outlined, as are results from detailed 3D PIC simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL058
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TUPAL062	Recent Developments for Cyclotron Extraction Foils at TRIUMF	electron, extraction, cyclotron, TRIUMF	1159
	Y. Bylinskii, R.A. Baartman, P.E. Dirksen, Y.-N. Rao, V.A. Verzilov TRIUMF, Vancouver, Canada
	Funding: Funded under a contribution agreement with NRC (National Research Council Canada). The TRIUMF 500 MeV H− cyclotron employs stripping foils to extract multiple beams for different experimental programs. The upgrades in foil material and foil holders lead to significant improvements in beam quality and foil life time, as well as reduction of Be-7 contamination originated in the foils. Thus, an accumulated beam charge extracted with a single foil increased from ~60 mA·hours to more than 500 mA·hours. A key role that lead to these advances was an understanding of the foil heating mechanism, major contribution to which is paid by the power deposition from electrons stripped by the foil. To further diminish this effect, we recently introduced a foil tilt from the vertical orientation that allows stripped electrons fast escape from the foil, well before losing their original momentum through the heat deposition. Other improvements were related to operational issues. Introduction of a "combo" foil consisting of wide portion and thin wire allowed both high and low intensity beam extraction without foils sacrifice. Deploying a wedge foil for extraction at 100 MeV helped reduction of beam intensity instabilities caused by beam vertical size and position fluctuations.
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TUPAL068	The Development of a Nw Fast Harmonic Kicker for the JLEIC Circulator Cooling Ring	kicker, cavity, emittance, electron	1171
	G.-T. Park, F. Fors, J. Guo, R.A. Rimmer, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. After the first half-scale, 5 harmonic kicker cavity prototyping * for the JLEIC's CCR/ERL electron cooler and the beam dynamic simulation study of the 10-turn CCR *. The optimized circulation cooling turns has been changed to 11 and only 5 odd-harmonic modes from 86.6 MHz to 779.4 MHz plus a DC bias are needed for the harmonic RF kicker system. The new cavity design including the electromagnetic and thermal cooling optimization and its 11 turns beam bunch tracking simulation with the new numerology of RF deflecting voltages will be presented. Further design specifications for its RF harmonic drive and the broadband RF window, coupler and circulator component will be given for handling 5 kW of total RF power. Y, Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 122001 (2016). ** Y. Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 084201 (2016).
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TUPAL069	Experimental Demonstration of Ion Beam Cooling with Pulsed Electron Beam	electron, experiment, synchrotron, data-analysis	1174
	Y. Zhang, A. Hutton, K. Jordan, T. Powers, R.A. Rimmer, M. F. Spata, H. Wang, S. Wang, H. Zhang JLab, Newport News, Virginia, USA J. Li, X.M. Ma, L.J. Mao, M.T. Tang, J.C. Yang, X.D. Yang, H. Zhao, H.W. Zhao IMP/CAS, Lanzhou, People's Republic of China
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Cooling ion beams at high energy is presently considered for several ion colliders, in order to achieve high luminosities by enabling a significant reduction of emittance of hadron beams. Electron beam at cooling channel in a few to tens MeV can be accelerated by a RF/SRF linac, and thus using bunched electrons to cool bunched ions. To study such cooling process, the DC electron gun of EC35 cooler at the storage ring CSRm, IMP was modified by pulsing the grid voltage. A 0.07-3.5 micro-second pulse length with a repetition frequency of less than 250 kHz and synchronized with the ion revolution frequency was obtained. The first experimental demonstration of cooling of a coasting and bunched ion beam by a pulsed electron beam was carried out. Data analysis indicates the bunch length shrinkage and the momentum spread reduction of bunched 12C+6 ion beam as evidence of cooling. A longitudinal grouping effect of the coasting ion beam by the electron pulses has also been observed. In this paper, we will present experimental results and comparison to the simulation modelling, particularly on the bunched electron cooling data after carefully analyzing the beam diagnostic signals. L.J. Mao et al., Experimental Demonstration of Electron Cooling with Bunched Electron Beam, TUP15, Proceedings of COOL2017, Bonn, Germany
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TUPAL075	Mechanical Design and Error Analysis of a 325 MHz IH-DTL Test Cavity	DTL, alignment, cavity, linac	1186
	R. Tang, C.T. Du, X. Guan, K.D. Man, C.-X. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng TUB, Beijing, People's Republic of China J. Li NUCTECH, Beijing, People's Republic of China
	A 325 MHz interdigital H-mode drift tube linac (IH-DTL) test cavity with a modified KONUS beam dynamics is under fabrication at Tsinghua University. The inner diameter of the tank increases from 196.8 to 232.6 mm. The mechanical design is considered carefully because of its small geometry. A three-piece design has been adopted in the mechanical design. The error analysis is carried out to determine the error requirement of machining and alignment. The details of mechanical design and error analysis is presented.
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TUPAL076	Result of the First Muon Acceleration with Radio Frequency Quadrupole	rfq, acceleration, experiment, target	1190
	R. Kitamura University of Tokyo, Tokyo, Japan S. Bae, B. Kim SNU, Seoul, Republic of Korea Y. Fukao, K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, M. Otani, T. Yamazaki KEK, Tsukuba, Japan K. Hasegawa, Y. Kondo, T. Morishita JAEA/J-PARC, Tokai-mura, Japan H. Iinuma, Y. Nakazawa Ibaraki University, Ibaraki, Japan G.P. Razuvaev Budker INP & NSU, Novosibirsk, Russia N. Saito J-PARC, KEK & JAEA, Ibaraki-ken, Japan Y. Sue Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
	Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784. J-PARC E34 experiment aims to measure the muon g-2/EDM precisely with novel techniques including the muon linear accelerator. Slow muon source by the metal foil method in order to cool the muon beam has been developed for the muon acceleration test with RF accelerator, because the muon beam derived from the proton driver was the tertiary beam and has a large emittance. The first verification test of the muon acceleration with RFQ was carried out at the muon test beam line of J-PARC MLF in October 2017. The incident surface muons were decelerated by the thin metal foil target and produced the negative muonium ions (Mu-), which is the bound stat of a positive muon and two electrons. After Mu- were extracted by a electrostatic accelerator as the injector of the RFQ, they were accelerated with RFQ to 88.6 keV. The accelerated Mu- were identified by the momentum selection with the bending magnet after the RFQ, and the measurement of the Time-Of-Flight. Accelerated Mu- were easily distinguished from penetrated positive muons by the difference of the polarity. The latest analysis result of the world's first muon acceleration with RFQ will be reported in this paper.
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TUPAL077	2D-3D PIC Code Benchmarking/Anchoring Comparisons For a Novel RFQ/RFI LINAC Design	rfq, space-charge, linac, experiment	1194
	S.J. Smith, S. Biedron, A. M. N. Elfrgani, E. Schamiloglu University of New Mexico, Albuquerque, USA M.S. Curtin, B. Hartman, T. Pressnall, D.A. Swenson Ion Linac Systems, Inc., Albuquerque, USA K. Kaneta CICS, Tokyo, Japan
	Funding: *The study at the University of New Mexico was supported in part by DARPA Grant N66001-16-1-4042 and gift to the University of New Mexico Foundation by ILS. In this study, comparisons are made between several particle dynamics codes (namely CST Particle Studio, GPT, and upgraded PARMILA codes) in order to benchmark them. The structure used for the simulations is a novel 200 MHz, 2.5 MeV, CW RFQ/RFI LINAC designed by Ion Linac Systems (ILS). The structure design and parameters are provided, simulation techniques are explained, and results from all three code families are presented. These results are then compared with each other, identifying similarities and differences. Numerous parameters for comparison are used, including the transmission efficiency, Q-factor, E-field on axis, and beam properties. Preliminary anchoring between modeling and simulation performance predictions and experimental measurements will be provided.
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TUZGBF5	KlyLac Prototyping for Borehole Logging	klystron, linac, cavity, feedback	1244
	A.V. Smirnov, R.B. Agustsson, M.A. Harrison, A.Y. Murokh, A.Yu. Smirnov RadiaBeam Systems, Santa Monica, California, USA S. Boucher, T.J. Campese, K.J. Hoyt RadiaBeam, Los Angeles, California, USA E.A. Savin MEPhI, Moscow, Russia A.A. Zavadtsev Nano, Moscow, Russia
	Funding: Work supported by the U.S. Department of Energy (award No. DE-SC0015721) Linac-based system for borehole logging exploits KlyLac approach combing klystron and linac sharing the same electron beam, vacuum volume, and RF network enabling self-oscillation due to a positive feedback. The KlyLac prototype design tailors delivering ~1 MeV electrons in a linac section using part of the beam injected from a sheet beam klystron (SBK). The linac part is based on a very robust, high group velocity, cm-wave, and a standing wave accelerating structure of a 'cross-pin' type supplied by a sampler. The SBK part features a permanent magnet solenoid focusing, relatively low voltage, and high aspect ratio beam. The main SBK characteristics (perveance, power, and efficiency) are expected to be similar to that for a magnetron.
	Slides TUZGBF5 [3.280 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUZGBF5

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MOPMF006

Test of Stepwise Electron Bunch Replacement in eRHIC Using an Electron Lens in RHIC

electron, emittance, proton, experiment

95

W. Fischer, M.R. Costanzo, A.V. Fedotov, X. Gu, A. Marusic, M.G. Minty, C. Montag, Y. Tan, P. Thieberger
BNL, Upton, Long Island, New York, USA

Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy.
The electron-ion collider eRHIC requires an electron bunch replacement about every second to maintain both high luminosity and polarization. If the bunch can be replaced in several steps, the requirements for both the electron gun and the electron accelerator are greatly reduced due to the reduced bunch charge. However, a stepwise replacement of electron bunches in eRHIC will give rise to transient effects from the beam-beam interaction that will lead to emittance growth. Such a scheme was tested using one of the RHIC electron lenses with a multiple step increase of the electron current. The test provides an order-of-magnitude estimate of the effect without any further mitigating measures.

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MOPMF010

Measurement and Simulation of Betatron Coupling Beam Transfer Function in RHIC

coupling, betatron, experiment, quadrupole

99

Y. Luo, W. Fischer, A. Marusic, M.G. Minty
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Transfer function measurements are important for characterizing betatron tunes, betatron coupling, and beam spectrum in the routine operation of the Relativistic Heavy Ion Collider (RHIC). To counteract the linear betatron coupling, we developed a technique to continuously measure the betatron coupling coefficient with a base band phase lock loop tune meter in 2006. Based on this technique, we demonstrated and built a robust tune/coupling feedback in RHIC. In this article, we revisit the BTF measurement with betatron coupling to benchmark our BTF simulation code. We also compared the values of eigenmode projection ratios from BTF with those calculated with the single particle model.

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MOPMF011

Beam-Beam Issues With Two Interaction Points in eRHIC

proton, electron, detector, luminosity

102

Y. Luo, M. Blaskiewicz, A. He, C. Montag, V. Ptitsyn
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In this article, we study the beam-beam interaction related issues with two interaction points in the current eRHIC ring-ring design. We carried out strong-strong beam-beam simulation in a 2-d bunch intensity scan. We observed coherent beam-beam instability and emittance blowup with 2 collisions per turn at lower bunch intensities than the case with only 1 collision per turn. To deliver collisions to the two experiments simultaneously, we proposed a new bunch filling pattern to avoid 2 collisions per turn for any electron or proton bunch. We proved that the parasitic beam-beam effect with the new bunch filling pattern is negligible.

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MOPMF012

Study of Crabbed Collision in eRHIC With a Combination of Strong-Strong and Weak-Strong Simulations

electron, proton, cavity, luminosity

105

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the present design of the future electron-ion collider eRHIC at the Brookhaven National Laboratory, a crossing angle of 22~mrad between the electron and proton orbits at the interaction region is adopted. To compensate the geometric luminosity loss, a local compensation scheme with two sets of crab cavities for each beam is considered. In this article, we first carry out strong-strong beam-beam simulation to study possible coherent beam-beam instability. Under the assumption of no coherent beam-beam motion, we then carry out a weak-strong beam-beam simulation to determine the long-term stability of the proton beam with the equilibrium electron beam sizes extracted from the strong-strong beam-beam simulation.

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MOPMF014

Polarization at eRHIC Electron Storage Ring, an Ergodic Approach

polarization, electron, lattice, storage-ring

112

F. Méot
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Based on considerations of ergodicity of the dynamical system of an electron bunch at equilibrium, the preservation of polarization in an electron storage ring is estimated from the tracking of a very limited number of electrons. This has a substantial impact on required High Power Computing resources, in noticeable contrast with the method generally used that tracks tens of electron bunches, each comprised of thousands of particles, for several thousands of turns. It is also shown that a minimum number of tracking turns is required in order to ensure the numerical convergence of the linear regressions that yield depolarizing time constant values from tracking, in both methods.

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MOPMF018

Numerical Simulation of Spin Dynamics with Spin Flipper in RHIC

resonance, dipole, polarization, injection

118

P. Adams, H. Huang, J. Kewisch, F. Méot, P. Oddo, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, T. Roser
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Spin flipper experiments during RHIC Run 17 were performed to study its effectiveness as a method for polarization sign reversal during stores. Numerical simulations are reported here, which were performed in accompaniment of these, and are being pursued with the aim of accurately reproducing the experimental conditions and providing thorough insight in the role of various key parameters participating in the dynamics of the spin flip, such as the sweep rate of the AC dipole, chromatic orbit control at RHIC snakes, RF parameters, possible effects of non-linear spin resonances, mirror resonance, tolerance on flipper magnet parameters, etc. The ultimate goal is for these simulations to serve as a guidance toward perfect flip to allow routine use during physics Runs.

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MOPMF022

Luminosity Reduction Caused by the Full-Detuning LLRF Scheme on the HL-LHC Crab Cavities

luminosity, cavity, proton, LLRF

129

E. Yamakawa, R. Apsimon, A.C. Dexter
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
P. Baudrenghien, R. Calaga, F.J. Galindo Guarch
CERN, Geneva, Switzerland

The High-Luminosity LHC (HL-LHC) crab cavities (CCs) will be installed on both sides of IP1 (ATLAS) and IP5 (CMS) to compensate for the geometric luminosity reduction due to the crossing angle. To cope with the increased beam current (0.55 A DC for LHC, 1.1 A for HL-LHC), the operation of the LLRF system has been changed: rather than fully compensating the transient beam loading, we allow the phase to vary along the turn (100 ps peak-peak with 1.1 A DC). This has been implemented at LHC since July 2017. The CCs have high loaded Q (5e5) and the available RF power is insufficient to follow the bunch phase modulation. The crabbing voltage is not modulated, causing a phase error w.r.t. the individual bunch centroids, leading to transverse kicks of the centroids and an asymmetric crabbing of the bunch cores. We present an analytical model for the resulting luminosity reduction and validate with particle tracking simulations. Due to the symmetry of the bunch filling patterns for the counter-rotating beams, the peak luminosity is reduced by only 2% for nominal HL-LHC parameters at IPs 1 and 5, which is within tolerable limits.

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MOPMF028

A Superconvergent Algorithm for Invariant Spin Field Stroboscopic Calculations

resonance, polarization, storage-ring, lattice

145

D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: National Science Foundation and the Department of Energy
Stroboscopic averaging can be used to calculate the invariant spin field \bfn for particles with a finite oscillation amplitude in phase space. The standard technique starts with making a guess for \bfn(\bfr), which is a function of the phase space position \bfr. By tracking a particle's orbital position forward in time and then projecting the guessed \bfn backwards to the starting phase space point, the average of the backward projected spins will converge to the invariant spin direction linearly as 1/N where N is the number of turns tracked. The convergence can be accelerated by an iterative method that uses an approximate invariant spin field constructed by averaging the calculated spin field over points that are close in orbital phase space. This superconvergent algorithm has been built into a new program based upon the Bmad toolkit for charged particle and X-ray simulations.

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MOPMF038

Cleaning Performance of the Collimation System with Xe Beams at the Large Hadron Collider

collimation, betatron, heavy-ion, proton

176

N. Fuster-Martínez, R. Bruce, P.D. Hermes, J.M. Jowett, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland

The LHC heavy-ion program with Pb ions has delivered substantial physics results since the startup of the LHC. There was a Xe run in 2017 in which collimation losses and cleaning were assessed. These studies give a unique opportunity for very valuable benchmark of simulation models with measurements, which could also be very important to understand limitations for future runs with Pb and other species. In this paper, we present collimation loss maps measured in the first ever operation of the LHC with Xe ions. The measurements are compared with simulations and first conclusions are discussed for possible future operation.

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MOPMF040

Crossing Angle Anti-Leveling at the LHC in 2017

luminosity, operation, proton, experiment

184

N. Karastathis, K. Fuchsberger, M. Hostettler, Y. Papaphilippou, D. Pellegrini
CERN, Geneva, Switzerland

In 2017, LHC incorporated in operation an anti-leveling procedure of adapting in steps the crossing angle of the colliding beams to increase the integrated luminosity. In this paper, we present the Dynamic Aperture simulations that were employed to identify the operational margins, and therefore define the leveling steps. The results are complemented by observations from nominal operation and projections for the 2018 operation. Additional anti-leveling techniques, investigated in dedicated machine studies are also discussed

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MOPMF043

Tuning of CLIC-Final Focus System 3 TeV Baseline Design Under Static and Dynamic Imperfections

luminosity, ISOL, collider, linear-collider

196

E. Marín, A. Latina, J. Pfingstner, D. Schulte, R. Tomás
CERN, Geneva, Switzerland
J. Pfingstner
University of Oslo, Oslo, Norway

In this paper we present the tuning study of the Compact Linear Collider - Final Focus System (CLIC-FFS) 3~TeV baseline design under static and dynamic imperfections for the first time. The motion of the FFS magnets due to ground motion and the impact of active and passive mechanisms envisaged to stabilize both e^- and e⁺ systems are described. It is found that the Pre-isolator required for stabilization of the Final Doublet drives the performance of the collider at the final stages of the tuning process. The obtained tuning performance depending on the stabilization techniques are discussed in detail.

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MOPMF044

New Coordination Tools to Prepare Programmed Stops in the LHC and its Injectors

hardware, MMI, dipole, FEL

200

S. Chemli, M. Bernardini, T.W. Birtwistle, A. Bolognesi, B. Brito Da Palma, S.E. Bustamante, J. Coupard, K. Foraz, E. Kleszcz, N. Kotsolakos, T. Krastev, P. A. Kulig, Y. Muttoni, B. Nicquevert, L. Pater, A. Patrascoiu, S. Petit, C. Rauser, A. Wardzinska
CERN, Geneva, Switzerland

The LHC and its Injectors are submitted to an overall lifecycle of three to four years of physics delivery to Experiments with a two-year long stop, also known as Long Shutdown (LS). The years of physics delivery are ended by a programmed stop for the immediate preventive and corrective maintenance, also known as (Extended)-Year-End Technical Stop - (E)YETS. This regular cycle is to be addressed in parallel with other projects: the upgrade projects to the accelerator complex of the LHC (High-Luminosity project) and to its Injectors (LHC Injectors Upgrade), and the "standard" consolidation tasks. This paper describes the way the programmed stops coordination group prepares the activities to take place during the stop with a set of new tools and processes that ease the communication between the stakeholders of the coordination.

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MOPMF046

Simulation of Hydrodynamic Tunneling Caused by High Energy Proton Beam in Copper through Coupling of FLUKA and Autodyn

target, proton, collider, coupling

204

Y.C. Nie, A. Bertarelli, F. Carra, C. Fichera, L.K. Mettler, R. Schmidt, D. Wollmann
CERN, Geneva, Switzerland

For machine protection of high-energy colliders, it is important to assess potential damages caused to accelerator components in case large number of bunches are lost at the same place. The numerical assessment requires an iterative execution of an energy-deposition code and a hydrodynamic code, since the hydrodynamic tunneling effect will likely play an important role in the beam-matter interactions. For proton accelerators at CERN and for the Future Circular Collider (FCC), case studies were performed, coupling FLUKA and BIG2. To compare different hydrocodes and not to rely only on BIG2, FLUKA and a commercial tool, Autodyn, have been used to perform these simulations. This paper reports a benchmarking study against a beam test performed at the HiRadMat (High-Radiation to Materials) facility using beams at 440 GeV from the Super Proton Synchrotron. Good agreement has been found between the simulation results and the test as well as previous simulations with FLUKA and BIG2, particularly in terms of penetration depth of the beam in copper. This makes the coupling of FLUKA and Autodyn an alternative solution to simulating the hydrodynamic tunneling. More case studies are planned for FCC and other high-beam-power accelerators.

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MOPMF055

Update of the CLIC Positron Source

positron, target, linac, electron

236

Y. Han, L. Ma
SDU, Shandong, People's Republic of China
C. Bayar
Ankara University, Faculty of Sciences, Ankara, Turkey
S. Döbert, A. Latina, D. Schulte
CERN, Geneva, Switzerland

The baseline positron source of CLIC has been optimised for the 3 TeV c.o.m. energy. Now the first stage of the CLIC is proposed to be at 380 GeV. Recently, the positron transmission efficiency from the tungsten target to the damping rings injection has been improved by 2.5 times. This opened the possibility for an optimisation of the whole positron source, comprising the injector linacs, aimed at improving its performance and its overall power efficiency. In this paper the key parameters of the positron source, which include the current and the energy of the primary electron beam, the thickness of the crystal and amorphous tungsten targets, the distance between the two targets, the adiabatic matching device (AMD) and pre-injector linacs, are optimized to improve the overall power efficiency.

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MOPMF062

Upgrade of the Dilution System for HL-LHC

kicker, operation, Windows, damping

261

C. Wiesner, W. Bartmann, C. Bracco, M. Calviani, E. Carlier, L. Ducimetière, M.I. Frankl, M.A. Fraser, S.S. Gilardoni, B. Goddard, T. Kramer, A. Lechner, N. Magnin, A. Perillo-Marcone, T. Polzin, E. Renner, V. Senaj
CERN, Geneva, Switzerland

The LHC Beam Dump System is one of the most critical systems for reliable and safe operation of the LHC. A dedicated dilution system is required to sweep the beam over the front face of the graphite dump core in order to reduce the deposited energy density. The High Luminosity Large Hadron Collider (HL-LHC) project foresees to increase the total beam intensity in the ring by nearly a factor of two, resulting in a correspondingly higher energy deposition in the dump core. In this paper, the beam sweep pattern and energy deposition for the case of normal dilution as well as for the relevant failure cases are presented. The implications as well as possible mitigations and upgrade measures for the dilution system, such as decreasing the pulse-generator voltage, adding two additional kickers, and implementing a retrigger system, are discussed.

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MOPMF068

Quantum Excitation due to Classical Beamstrahlung in Circular Colliders

collider, photon, emittance, radiation

281

M.A. Valdivia García, D. El Khechen, K. Oide, F. Zimmermann
CERN, Geneva, Switzerland

In the collisions of proposed future circular colliders, like FCC-ee and CEPC, the beamstrahlung regime is classical, i.e. with an "Upsilon parameter" much smaller than 1. In the classical regime, for a constant electromagnetic field a simple relation exists between the average photon energy u and the average squared photon energy u², which is the same as for standard synchrotron radiation in storage rings. This relation breaks down, however, if the electromagnetic field is not constant in time and position, as is the case for a beam-beam collision. We derive an analytical expression for u²/u², considering the case of Gaussian-bunch collisions with crossing angle (and possibly crab waist). We compare our result with the photon energies obtained in beam-beam simulation for FCC-ee at beam energies of 45.6 GeV and 175 GeV, using the two independent codes BBWS and Guineapig. Finally, we re-optimize the FCC-ee parameters of a possible mono-chromatization scheme for direct Higgs production at 125 GeV, derived previously, by applying the refined expression for the rms photon energy.

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MOPMF070

High Voltage Design for the Electrostatic Septum for the Mu2e Beam Resonant Extraction

cathode, high-voltage, vacuum, extraction

289

M.L. Alvarez, C.C. Jensen, D.K. Morris, V.P. Nagaslaev, H. Pham, D.G. Tinsley
Fermilab, Batavia, Illinois, USA

Two electrostatic septa (ESS) are being designed for the slow extraction of 8GeV proton beam for the Mu2e experiment at Fermilab. Special attention is given to the high voltage components that affect the performance of the septa. The components under consideration are the high voltage (HV) feedthrough, cathode standoff (CS), and clearing electrode ceramic standoffs (CECS). Previous experience with similar HV systems at Fermilab was used to define the evaluation criteria of the design of the high voltage components. Using electric field simulation software, high E-field intensities on the components and integrated field strength along the surface of the dielectric material were minimized. Here we discuss the limitations found and improvements made based on those studies.

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MOPMF085

Beam-gas Background Characterization in the FCC-ee IR

scattering, background, vacuum, optics

322

M. Boscolo, O.R. Blanco-García
INFN/LNF, Frascati (Roma), Italy
H. Burkhardt, R. Kersevan, M. Lueckhof
CERN, Geneva, Switzerland
F. Collamati
INFN-Roma1, Rome, Italy

The MDISim toolkit is used to evaluate and characterize the beam-gas induced background in the FCC-ee Interaction Region. MDISim allows a full characterization of this beam background source with the locations where the beam-gas scattering occurs as well as the loss points, as a function of different vacuum conditions and composition, for the nominal optics and parameters. Detailed pressure distribution profiles have been obtained running coupled synchrotron radiation and molecular flow montecarlo codes, as an input to the GEANT4 calculations. The particles hitting the pipe in the IR can be tracked in the detectors with a full Geant-4 simulation. Semi-analytic estimates for the expected rates and lifetime are also performed.

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MOPMF090

First Studies of Ion Collimation for the LHC Using BDSIM

collimation, hadron, heavy-ion, proton

341

A. Abramov, S.T. Boogert, L.J. Nevay, S.D. Walker
JAI, Egham, Surrey, United Kingdom

At the Large Hadron Collider (LHC) at CERN ion physics runs are performed in addition to proton physics runs. In ion operation the cleaning efficiency of the collimation system is lower than in the case of protons and the ion showering process is more complicated and produces a larger variety of secondary particles. In particular, lighter ion species can be produced as fragmentation products in the collimation system and specialised physics lists are required to simulate their production and propagation in matter. The Geant4 toolkit offers comprehensive physics process lists that extend to the case of arbitrary ion species at high energies. First results from a study of ion collimation for the LHC using the Geant4 physics library in BDSIM are presented here. These include simulations of a full ring loss map and particle spectra for collimator leakage for a Pb beam at injection energy in the LHC.

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MOPMK010

Study Progress of the Coupling Resonance of the Crab Crossing Scheme in Electron-Ion Collider

luminosity, electron, synchrotron, cavity

368

Y. Hao
FRIB, East Lansing, USA
Y. Luo, V. Ptitsyn
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Crab crossing scheme is essential collision scheme to achieve high luminosity for the future electron-ion collider (EIC). The bunch length effect of the ion beam cannot be ignored even when cooling is present compared with the wavelength of the crab cavity, therefore, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the ion beam, hence an impact to the luminosity lifetime. In this paper, we present the result of numerical beam dynamics studies of the crab crossing scheme. The result indicates that there is a special coupling resonance in the nonlinear relation of the crab crossing scheme of the EIC, which dominates the luminosity degradation. And we will discuss the possible remedies for such resonance.

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MOPMK012

Electron Cloud Studies in FCC-ee

electron, collider, quadrupole, vacuum

374

E. Belli
Sapienza University of Rome, Rome, Italy
P. Costa Pinto, G. Rumolo, T.F. Sinkovits, M. Taborelli
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy

Electron cloud effects are one of the most critical aspects for the LHC and the future circular colliders. In the frame of the electron-positron collider FCC-ee, an estimation of the electron cloud build up in the machine will be discussed in this paper. A preliminary evaluation of the heat load in the arc components and interaction region magnets will be presented, together with possible mitigation strategies.

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MOPMK016

Calculations of Beam-Beam Effect and Luminosity for Crab Dynamics Simulations in JLEIC

luminosity, collider, electron, beam-beam-effects

386

H. Huang, V.S. Morozov, A.V. Sy
JLab, Newport News, Virgina, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contracts DE-AC05-06OR23177 and DE-AC02-06CH11357.
Crab crossing is an integral part of the Jefferson Lab Electron-Ion Collider (JLEIC) design to achieve high luminosity while meeting the detection and physics pro-gram requirements. The crab crossing scheme provides a head-on beam-beam collision for beams with a nonzero crossing angle. Simulations of crabbing dynamics currently do not include beam-beam effects. We describe a framework for accurate simulation of beam-beam effects on crabbing dynamics by applying a numerical calculation of the Bassetti-Erskine analytic solution to symplectic particle tracking codes. The numerical calculation is benchmarked against the analytic solution by calculating the luminosity reduction for several colliding beam scenarios. Benchmarking results show good agreement be-tween the numerical calculation and analytic solution, paving the way for implementation of the beam-beam kick to Elegant tracking simulations.

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MOPML006

Multi-Stage Electron Cooling Scheme for JLEIC

emittance, proton, electron, collider

397

H. Zhang, S.V. Benson, Y.S. Derbenev, Y. Roblin, Y. Zhang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and DE-AC02-06CH11357.
JLEIC is the future electron ion collider under design at Jefferson Lab, which will provide a luminosity up to 10³⁴ cm^-2s^-1. Electron cooling is essential for JLEIC to overcome the intrabeam scattering effect, reduce the ion beam emittance and thus achieve the high luminosity. The cooling time is approximately in proportion to the square of the energy and the 6D emittance. To avoid the difficulty of cooling the ion beam with large emittance at high energy, a multi-stage cooing scheme was designed for JLEIC. The ion beam was cooled at the low energy to reduce the emittance. Then it was ramped up to the collision energy. During the collision, electron cooling is implemented to maintain the emittance and the luminosity. Simulations for proton beam and lead ion beam at various stages are presented in this paper.

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MOPML010

Challenges and Status of Tuning Simulations for CLIC Traditional Beam Delivery System

luminosity, linear-collider, collider, lattice

412

R.M. Bodenstein, P. Burrows
JAI, Oxford, United Kingdom
E. Marín
CERN, Geneva, Switzerland

The beam delivery system (BDS) for the 3 TeV version of the Compact Linear Collider (CLIC) has two main design types. One type is referred to as the local scheme, as it is approximately one kilometer shorter and corrects the chromaticity in both planes. The other type is referred to as the traditional scheme, and separates the chromaticity correction of each plane into different areas. The expectation early in the studies was that the traditional scheme would be easier to tune. This work will address the problems experienced in tuning simulations for the traditional BDS and describe the current state of these simulations.

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MOPML012

Special Collimation System Configuration for the LHC High-Beta Runs

background, collimation, detector, experiment

418

H. Garcia Morales
Royal Holloway, University of London, Surrey, United Kingdom
R. Bruce, H. Burkhardt, M. Deile, S. Jakobsen, A. Mereghetti, S. Redaelli
CERN, Geneva, Switzerland

Special LHC high-beta optics is required for the forward physics program of TOTEM and ATLAS-ALFA. In this configuration, the beam is de-squeezed (the \beta-function at the collision point is increased) in order to minimize the divergence for measurements at very small scattering angles. In these low beam intensity runs, it is important to place the Roman Pots (RPs) as close as possible to the beam, which demands special collimator settings. During Run I, a significant amount of background was observed in the forward detectors due to particles outscattered from the primary collimator. During Run II, a different collimation configuration was used where a tungsten collimator was used as primary collimator instead of the usual one made of carbon. Using this configuration, a significant reduction of the background at the RPs was observed. In this paper we present a description of the new collimator configuration and the results obtained during the high-beta run carried out in 2016.

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MOPML020

Numerical Simulations to Evaluate and Compare the Performances of Existing and Novel Degrader Materials for Proton Therapy

scattering, emittance, proton, shielding

435

R. Tesse, A. Dubus, N. Pauly
ULB - FSA - SMN, Bruxelles, Belgium
C. Hernalsteens, W.J.G.M. Kleeven, F. Stichelbaut
IBA, Louvain-la-Neuve, Belgium

The performance of the energy degrader in terms of beam properties directly impacts the design and cost of cyclotron-based proton therapy centers. The aim of this study is to evaluate the performances of different existing and novel degrader materials. The quantitative estimate is based on detailed Geant4 simulations that analyze the beam-matter interaction and provide a determination of the beam emittance increase and transmission. Comparisons between existing (aluminium, graphite, beryllium) and novel (boron carbide and diamond) degrader materials are provided and evaluated against semi-analytical models of multiple Coulomb scattering. The results showing a potential in emittance reduction for novel materials are presented and discussed in detail.

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MOPML022

Development of Travelling Wave Accelerating Structure for a 10 MeV E-Linac

electron, bunching, radiation, linac

443

J.H. Yang, Y. Yang
CIAE, Beijing, People's Republic of China
G. Han
China Institute of Atomic Energy, Beijing, People's Republic of China

Electron irradiation processing is a vital application field of nuclear technology application. China Institute of Atomic Energy (CIAE) developed several 10 MeV high power electron irradiating accelerator successfully, promoting the development of high energy high power irradiating accelerator technology and electron irradiation processing in China. The paper introduced the development of a 10 MeV travelling wave accelerating tube. The tube operates at 2856 MHz in 2π/3 mode. The SUPERFISH and PARMELA are used for the physical design. Several methods are used for microwave parameter measurement and tuning. The high power test shows the beam energy is 10.3 MeV and average beam power is 24.3 kW.

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MOPML023

Very-High Energy Electron (VHEE) Studies at CERN's CLEAR User Facility

experiment, electron, scattering, proton

445

A. Lagzda, R.M. Jones
UMAN, Manchester, United Kingdom
A. Aitkenhead, K. Kirkby, R. MacKay, M. Van Herk
The Christie NHS Foundation Trust, Manchester, United Kingdom
R. Corsini, W. Farabolini
CERN, Geneva, Switzerland

Funding: Science and Technology Facilities Council (STFC) - United Kingdom
Here we investigate how inserts of various densities (0.001-2.2 g/cm³) affect the dose distribution properties of VHEE beams at ~150 MeV. A range variation comparison was also made with clinical proton beams using TOPAS/GEANT4 Monte Carlo simulations. In addition, we assess the viability of scattering foils for optimizing the size of VHEE beams for radiotherapy purposes. The experiments were conducted at CERN's CLEAR user facility.

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MOPML039

Comparison of Two Types of Steerers Applied in Proton Therapy Gantry

quadrupole, proton, superconductivity, radiation

488

Z.F. Zhao, Q.S. Chen, S. Hu, X. Liu, B. Qin, W. Wei
HUST, Wuhan, People's Republic of China
W. Chen
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China

A proton therapy project HUST-PTF (HUST Proton Therapy Facility) based on a 250MeV isochronous superconducting cyclotron is under development in Huazhong University of Science and Technology (HUST). Based on the optics design of the gantry, the steering magnets need to be placed in a compact structure, as well as meet the magnetic field requirement with a maximum deflection angle of ±5mrad@250MeV. In the paper, two types of steerers (O-shape and H-shape) were introduced and discussed in detail. The magnetic fringe field interference effects between quadrupoles and steerers were studied by using OPERA/TOSCA code. The result based on the contrastive analysis will give us a valuable reference to choose suitable steerers for proton therapy beamline.

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MOPML052

The Path to Compact, Efficient Solid-State Transistor-Driven Accelerators

cavity, electron, linac, impedance

520

D.C. Nguyen, C.E. Buechler, G.E. Dale, R.L. Fleming, M.A. Holloway, J.W. Lewellen, D. Patrick
LANL, Los Alamos, New Mexico, USA
V.A. Dolgashev, E.N. Jongewaard, E.A. Nanni, J. Neilson, A.V. Sy, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: Research presented in this work is supported by (LANL) Laboratory Directed Research and Development 20170521ER and by (SLAC) Department of Energy contract DE-AC02-76SF00515.
Small, lightweight, few-MeV electron accelerators that can operate with low-voltage power sources, e.g., solid-state transistors running on 50 VDC, instead of high-voltage klystrons, will provide a new tool to enhance existing applications of accelerators as well as to initiate new ones. Recent advances in gallium nitride (GaN) semiconductor technologies * have resulted in a new class of high-power RF solid-state devices called high-electron mobility transistors (HEMTs). These HEMTs are capable of generating a few hundred watts at S-, C- and X-bands at 10% duty factor. We have characterized a number of GaN HEMTs and verified they have suitable RF characteristics to power accelerator cavities **. We have measured energy gain as a function of RF power in a single low-beta C-band cavity. The HEMT powered RF accelerators will be compact and efficient, and they can operate off the low-voltage DC power buses or batteries. These all-solid-state accelerators are also more robust, less likely to fail, and are easier to maintain and operate. In this poster, we present the design of a low-beta, 5.1-GHz cavity and beam dynamics simulations showing continuous energy gain in a ten-cavity C-band prototype.
* See for example, http://www.wolfspeed.com/downloads/dl/file/id/463/product/174/cghv59350.pdf
** J.W. Lewellen et al., Proceedings of LINAC2016, Paper MO3A03

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MOPML054

Production and Collection of He-3 and Other Valuable Isotopes using Mu*STAR

controls, proton, MMI, interface

527

R.P. Johnson, R.J. Abrams, M.A. Cummings, T.J. Roberts
Muons, Inc, Illinois, USA

We propose an example facility based on GEM*STAR, an accelerator-driven molten-salt-fueled graphite-moderated thermal-spectrum reactor that can operate with different fissile fuels and uses a LiF-BeF2 molten eutectic carrier salt. In the first example, they propose using the 6Li in the LiF carrier to produce more than 2 kg/y of tritium (decaying to 3He with 12.3 year half-life) using a 2.5 MWb superconducting proton linac to drive the subcritical 500 MWt reactor burning surplus plutonium. The collection of other valuable fission-product radioisotopes like 133Xe will also benefit from the high temperature and continuous removal and separation afforded by fractional distillation

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MOPML055

Preliminary Physics Design of a Linac with the Variable Energy for Industrial Applications

linac, electron, gun, beam-loading

530

Zh. X. Tang
USTC, Hefei, Anhui, People's Republic of China
L. Wang, D.R. Xu
USTC/NSRL, Hefei, Anhui, People's Republic of China

This paper describes the physics design of a S-band (2856 MHz) linear accelerator (linac) with variable energy tuning. The system consists of a DC gun for generating electron, prebuncher for velocity modulation and two travelling wave (TW) accelerating sections for acceleration. The accelerating structure is a 2'Ð/3 mode constant gradient TW structure, which comprises TW buncher cells, followed by uniform cells. The structure is designed to accelerate 45 keV electron beam from the electron gun to 3.2 MeV, and then 10 MeV. An important feature of the TW linac is that the RF output power of the first linac is as the RF input power of the second linac. Three dimensional transient simulations of the accelerating structure along with the input and output couplers have been performed to explicitly demonstrate this feature. Beam dynamics is performed to calculate the beam parameter.

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MOPML060

Self-Consistent Simulation and Optimization of Space-Charge Limited Thermionic Energy Converters

electron, space-charge, cathode, feedback

543

N.M. Cook, J.P. Edelen, C.C. Hall
RadiaSoft LLC, Boulder, Colorado, USA
J.-L. Vay
LBNL, Berkeley, California, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0017162.
Thermionic energy converters (TEC) are an attractive technology for modular, efficient transfer of heat to electrical energy. The steady-state dynamics of a TEC are a function of the emission characteristics of the cathode and anode, an array of intra-gap electrodes and dielectric structures, and the self-consistent dynamics of the electrons in the gap. Proper modeling of these devices requires self-consistent simulation of the electron interactions in the gap. We present results from simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We consider the role of individual energy loss mechanisms in reducing device efficiency, including kinetic losses, radiative losses, and dielectric charging. We discuss the implementation of an external circuit model to provide realistic feedback. Lastly, we illustrate the potential to use nonlinear optimization to maximize the efficiency of these devices by examining grid transparency.

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MOPML061

Hadron Therapy Machine Simulations Using BDSIM

hadron, hadrontherapy, lattice, proton

546

W. Shields
JAI, Egham, Surrey, United Kingdom
S.T. Boogert, L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom
J. Snuverink
PSI, Villigen PSI, Switzerland

Minimising the background radiation dose in hadron therapy from particle losses and secondary emissions is of the highest importance for patient protection. To achieve this, tracking particles from source to the patient delivery region in a single simulation provides a quantitative description that distinguishes the background radiation from the treatment dose arriving at the gantry's isocentre. We demonstrate the ability to simulate beam transport, particle loss studies, and background radiation tracking in an example hadron therapy machine using BDSIM, a Geant4 based Monte Carlo simulation code for tracking high energy particles within a particle accelerator and its surrounding environment. Machine optics verification is also demonstrated through comparison to existing accelerator tracking codes.

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MOPML069

Enhancing Hadron Therapy through OMA

proton, FEL, medical-accelerators, hadron

568

C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie SkłodowskaCurie grant agreement No 675265.
Continued research into the optimization of medical accelerators is urgently required to assure the best possible cancer care for patients and this is one of the central aims of the OMA project which received 4 M€ of funding from the European Commission. A consortium of universities, research and clinical facilities, as well as partners from industry carry out an interdisciplinary R&D program across three closely interlinked scientific work packages. These address the development of novel beam imaging and diagnostics systems, studies into treatment optimization including innovative schemes for beam delivery and enhanced biological and physical models in Monte Carlo codes, as well as R&D into clinical facility design and optimization to ensure optimum patient treatment along with maximum efficiency. Selected research highlights from across these work packages will be presented and the impact on hadron therapy facilities around the world discussed.

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MOPML070

Thermal and Stress Analysis of an X-Ray Target for 6 MeV Medical Linear Accelerators

target, electron, site, photon

572

Z.H. Wang, H.B. Chen, J. Shi, H. Zha
TUB, Beijing, People's Republic of China

We present an optimal design of an X-ray target for 6 MeV medical linear accelerators using FLUKA simula-tions. The target is composed of high-atomic number tungsten and high-thermal conductivity copper, corre-sponding water-cooling system is showed too. Further-more, we analyse the temperature and thermal stress re-sponses of the target under transient thermal loads using Ansys Code. For 6 MeV electron beam with 100 uA cur-rent, the results show that the target can achieve 1014 cGy/min at 1meter in front of the target. Within 100 ms, the maximum temperature reaches 512 °C under pulsed heating source with 250 Hz frequency and 1' duty cycle and the number of cycles to failure is estimated as 5.8·10⁸.

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TUXGBF3

Reduction of the Kicker Impedance Maintaining the Performance of Present Kicker Magnet at RCS in J-PARC

kicker, impedance, synchrotron, extraction

616

Y. Shobuda, Y. Irie, T. Takayanagi, T. Togashi, K. Yamamoto, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The present kicker at RCS in J-PARC is designed to make a waveform by superposing the forward and backward currents from the power source to extract beams, so that one terminal of the kicker is shorted and the other one is open. On the other hand, the kicker impedance is the dominant source of the beam instability at the RCS. This report proposes a scheme to reduce the kicker impedance, maintaining the beneficial of the superposition of currents with the present kicker magnet.

Slides TUXGBF3 [9.947 MB]

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TUXGBF4

ORBIT Simulation, Measurement and Mitigation of Transverse Beam Instability in the Presence of Strong Space Charge in the 3-GeV RCS of J-PARC

impedance, injection, acceleration, space-charge

620

P.K. Saha, H. Harada, N. Hayashi, H. Hotchi, Y. Shobuda, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The transverse impedance of eight extraction pulse kicker magnets (KM) is extremely strong source of transverse beam instability in the 3-GeV RCS (Rapid Cycling Synchrotron) at J-PARC. To realize the designed 1 MW beam power, collective beam dynamics with including the space charge effect for the coupled bunch instabilities excited by the KM impedance and associated measures were studied by incorporating all realistic time-dependent machine parameters in the ORBIT 3-D particle tracking code. The simulation results were all reproduced by measurements and, as a consequence, an acceleration of 1 MW beam power has been successfully demonstrated. In order to maintain variation of the RCS parameters required for multi-user operation, realistic measures for beam instability mitigation were proposed and also been successfully implemented in reality. To further increase the RCS beam power, beam stability issues and possible measures beyond 1 MW beam power are also considered.

Slides TUXGBF4 [2.241 MB]

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TUYGBD4

Beam Loss Background and Collimator Design in CEPC Double Ring

detector, scattering, background, radiation

632

S. Bai, J. Gao, H. Geng, D. Wang, Y. Wang, C.H. Yu, Y. Zhang
IHEP, Beijing, People's Republic of China

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center of mass energy of 240 GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. Radiative Bhabha scattering and Beamstrahlung effects are dominant mechanism of the beam induced backgrounds at CEPC due to the beam lifetime. In this paper, we evaluated the beam loss background in simulation and designed a series of collimators to suppress the radiation level on the machine and the detector.

Slides TUYGBD4 [0.791 MB]

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TUPAF005

Status of AC-Dipole Project at RHIC Injectors for Polarized Helions

dipole, booster, resonance, proton

669

K. Hock, H. Huang, F. Méot, P. Oddo, N. Tsoupas, J.E. Tuozzolo, K. Zeno
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Polarized helions will be used in the eRHIC collider to collide with polarized electrons. To allow efficient transport of polarized helions in the Booster, to rigidities sufficiently high (B rho=10.8 T.m, |G gamma|=10.5) for minimizing the optical perturbations from the two partial helical dipoles in the AGS, an upgrade for overcoming depolarizing intrinsic resonances is needed. An AC-dipole is being designed to induce spin flips through intrinsic resonances. Booster AC-dipole operation will be established with protons while the polarized helion source is being completed. This paper reports the status of the project (which is now well advanced after two years of theoretical and design studies) and provides an overview of proof of principle experiments to take place after successful installation of the AC-dipole, during RHIC Run 19 with polarized proton beams.

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TUPAF025

Multi-turn Study in FLUKA for the Design of CERN-PS Internal Beam Dumps

dumping, experiment, operation, proton

724

J.A. Briz Monago, M. Calviani, F. Cerutti, J.J. Esala, S.S. Gilardoni, F.-X. Nuiry, G. Romagnoli, G. Sterbini, V. Vlachoudis
CERN, Geneva, Switzerland

The CERN Proton-Synchrotron (PS) accelerator is currently equipped with two internal beam dumps in operation since the 1970's. An upgrade is required to be able to withstand the beams that will be produced after the end of the LIU (LHC Injector Upgrade) project. For the design of the new dumps, the interaction and transport of beam and all secondary particles generated has been simulated using FLUKA. The working principle of the internal beam dump in the PS ring is very peculiar with respect to the other dumps in the CERN accelerator complex. A moving dump intercepts the circulating beam during few milliseconds like a fast scraper. The moving dump shaving the beam, the multi-turn transport of beam particles in the PS accelerator and a time-dependent energy deposition in the dump were modeled. The methodology and the results obtained in our studies for the dump core and downstream equipment will be reported in this contribution.

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TUPAF027

CERN PS Kicker for Proton Injection: from Beam-Based Waveform Measurements to Hardware Improvements

kicker, injection, emittance, flattop

732

V. Forte, A. Ferrero Colomo, M.A. Fraser, T. Kramer
CERN, Geneva, Switzerland

For 2017 operation, the termination mode of the CERN Proton Synchrotron (PS) horizontal injection kicker was permanently changed to short-circuited, to be compliant with the future performances requested by the LHC Injectors Upgrade (LIU) project. An extensive campaign of measurements was performed through a dedicated beam-based technique. The measurements identified possibilities for optimisation of the kicker system and were fundamental to properly tune the PSpice simulation model of the kicker, as well as for validating the hardware changes. The model was finally used to estimate the horizontal emittance growth for the future injection schemes in the PS.

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TUPAF028

Energy Deposition Studies and Analysis of the Quench Behavior in the Case of Asynchronous Dumps During 6.5 TeV LHC Proton Beam Operation

superconducting-magnet, proton, quadrupole, kicker

736

M.I. Frankl, W. Bartmann, M. Bednarek, C. Bracco, A. Lechner, A.P. Verweij, C. Wiesner, D. Wollmann
CERN, Geneva, Switzerland

The CERN LHC beam dumping system comprises a series of septa and fast-pulsed kicker magnets for extracting the stored proton beams to the external beam dumps. Different absorbers in the extraction region protect superconducting magnets and other machine elements in case of abnormal beam aborts, where bunches are swept across the machine aperture. During Run 2 of the LHC, controlled beam loss experiments were carried out at 6.5 TeV probing the particle leakage from protection devices under realistic operation conditions. This paper presents particle shower simulations analyzing the energy deposition in superconducting coils and assessing if the observed magnet quenches are compatible with the presently known quench limits.

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TUPAF030

Electron Cloud Build Up for LHC Sawtooth Vacuum Chamber

electron, vacuum, photon, synchrotron

744

G. Guillermo Cantón, F. Zimmermann
CERN, Geneva, Switzerland
G.H.I. Maury Cuna, E. D. Ocampo
Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico

At high proton-beam energies, beam-induced synchrotron radiation is an important source of heating, of beam-related vacuum pressure increase, and of primary photoelectrons, which can give rise to an electron cloud. For the arcs of LHC a sawtooth pattern had been imprinted on the horizontally outward side of the vacuum chamber in order to locally absorb synchrotron radiation photons without dispersing them all around the chamber. Using the combination of the codes Synrad3D and PyCLOUD we examine the effect of realistic absorption distributions with and without sawtooth on the build up of electron clouds.

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TUPAF031

Beam Simulation Studies for the Upgrade of the SPS Beam Dumping System

kicker, dumping, operation, injection

747

C. Heßler, W. Bartmann, E. Carlier, L. Ducimetière, B. Goddard, F.M. Velotti
CERN, Geneva, Switzerland

The SPS at CERN currently uses a beam dumping system that is installed in the long straight section 1 (LSS1) of the SPS. This system consists of two beam stopper blocks for low and high energy beams, as well as two vertical and three horizontal kicker magnets, which deflect and dilute the beam on the dumps. Within the frame of the LHC injector upgrade project (LIU) the beam dumping system will be relocated to long straight section 5 (LSS5) and upgraded with an additional vertical kicker, new main switches and a single new beam dump, which covers the full energy range. The impact of a possible increase of the vertical kicker rise time on the beam has been studied in simulations with MAD-X for the different optics in the SPS. Furthermore, the impact on the beam in failure scenarios such as the non-firing of one kicker has been investigated. The results of these studies will be presented and discussed in this paper. Operational mitigation methods to deal with an increased rise time will also be discussed.

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TUPAF035

Observations of SPS Slow-Extracted Spill Quality Degradation and Possible Improvements

extraction, quadrupole, power-supply, experiment

761

F.M. Velotti, H. Bartosik, K. Cornelis, M.A. Fraser, B. Goddard, S. Hirlaender, V. Kain, O. Michels, M. Pari
CERN, Geneva, Switzerland

The SPS delivers slow extracted proton and heavy ion spills of several seconds to the North Area fixed target experiments with a very high duty factor. Reduced machine reproducibility due to magnetic history and power supply ripples on the main circuits lead however to frequent degradation of the spill duty factor. In this paper, the measured effect of the SPS magnetic history on spill quality and principal machine parameters is presented. Another detailed measurement campaign was aimed at characterising the frequency content and response of the spill to noise on the main power supplies ripples. The main findings of this study will also be reported. Finally, simulations of possible improvements based on the data acquired are discussed, as well as an extrapolation to the possible spill quality after the implementation of the improvements.

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TUPAF037

Validation of the CERN PS Eddy Current Injection Septa

septum, vacuum, injection, HOM

768

M. Hourican, B. Balhan, J.C.C.M. Borburgh, T. Masson, A. Sanz Ull
CERN, Geneva, Switzerland

As part of the upgrade of the CERN PS accelerator from 1.4 GeV to 2 GeV, new injection septa have been developed. The system is comprised of a pulsed eddy current septum magnet and a pulsed eddy current bumper magnet. Both magnets will be housed in a common vacuum vessel and powered by independent power converters. In-depth studies and simulations have been performed to reduce as much as possible the leak field by designing specific magnetic shielding, combined with dual function beam impedance shielding. A prototype magnet was built and measured to validate the simulations. The final complete system will be bake-able at 200C and uses demineralised water for cooling. Closed circuit cooling systems have been integrated to reduce risks of vacuum leaks. This report describes the electromechanical design from the concept and simulation stages to the prototyping and final manufacturing. Results of the initial magnetic measurements, including field homogeneity and leak field mitigation methods are presented.

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TUPAF039

Electron Cooling Simulation and Experimental Benchmarks at LEIR

electron, plasma, experiment, solenoid

776

A. Latina, H. Bartosik, N. Biancacci, R. Corsini, D. Gamba, S. Hirlaender, A. Huschauer
CERN, Geneva, Switzerland

A fast and accurate simulation of Electron Cooling has recently been implemented in the tracking code RF-Track. The implementation, which is based on a "hybrid kinetic" model, enables the simulation of a large variety of realistic scenarios, including imperfections such as gradients in the electron density, misalignments of electrons / ions / solenoidal fields, both in the static and in the dynamic regimes. Benchmarks of the simulations against measurements performed at LEIR, using Lead and Xenon ions, are presented.

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TUPAF040

Beam Loss Measurements for Recurring Fast Loss Events During 2017 LHC Operation Possibly Caused by Macroparticles

proton, operation, dipole, insertion

780

A. Lechner, B. Auchmann, E. Bravin, A.A. Gorzawski, L. K. Grob, E.B. Holzer, B. Lindstrom, T. Medvedeva, D. Mirarchi, R. Schmidt, M. Valette, D. Wollmann
CERN, Geneva, Switzerland

The availability of the LHC machine was adversely affected in 2017 by tens of beam aborts provoked by frequent loss events in one standard arc cell (16L2). In most of the cases, the dumps were triggered by concurrently developing fast beam instabilities leading to particle losses in the betatron cleaning insertion. Many of the events started with a distinct sub-millisecond loss peak comparable to regular dust particle events, which have been observed along all the LHC since the start-up. In contrast to regular dust events, persistent losses developed in cell 16L2 after the initial peaks which can possibly be explained by a phase transition of macroparticles to the gas phase. In this paper, we summarize the observed loss characteristics such as spatial loss pattern and time profiles measured by Beam Loss Monitors (ionization chambers). Based on the measurements, we estimate the energy deposition in macroparticles and reconstruct proton loss rates as well as the gas densities after the phase transition. Differences between regular dust events and events in 16L2 are highlighted and the ability to induce magnet quenches is discussed.

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TUPAF046

Conceptual Design of a Collimation System for the CERN Super Proton Synchrotron

collimation, optics, proton, injection

802

M. Patecki, A. Mereghetti, D. Mirarchi, S. Redaelli
CERN, Geneva, Switzerland

The Super Proton Synchrotron (SPS) is the last accelerator in the LHC Injectors Chain. Its performance is constantly being improved in frame of the LHC Injectors Upgrade (LIU) Project in order to prepare it for the future HL-LHC (High Luminosity LHC) operation. One of the LIU goals is to nearly double the intensity extracted from the SPS, up to 2.32×10¹¹ p/bunch. In recent years, nearly 10% of losses are observed for nominal intensity and LHC-type beams; they grow to about 20% for the intensity approaching the HL-LHC target. Beam losses imply activation and aging of the SPS hardware; the possibility to add a collimation system is being considered to mitigate this problem. In this paper we present studies of a collimation system design for the SPS. The concept is based on a primary horizontal collimator located in an available position with high enough dispersion, and a secondary collimator to intercept the particles leaking out from the primary collimator. Performance of the proposed collimation system is evaluated by means of numerical simulations.

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TUPAF048

LIU Space Charge Studies for the LHC Pre-Accelerators

space-charge, injection, proton, resonance

810

F. Schmidt, H. Bartosik
CERN, Geneva, Switzerland

In 2011 a working group has been started to study performance limitations due to Space Charge (SC) in the four LHC pre-accelerators, LEIR, PSB, PS & SPS, in view of the LHC Injector Upgrade (LIU) project. To this end external and in-house simulation tools have been benchmarked for the LIU study cases with the long-term goal of providing a full sequence of tested CERN Space Charge tools. It became clear that SC studies must be combined with trustworthy models of the machines, including linear and non-linear errors. In particular an effective s-dependent non-linear model is required. Recent studies indicate that also the low frequency ripple spectrum due to conventional power supplies might play an important role for the beam dynamics in presence of space charge in the pre-injectors.

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TUPAF051

Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS

extraction, octupole, multipole, optics

822

L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard
CERN, Geneva, Switzerland
K.A. Brown
BNL, Upton, Long Island, New York, USA

Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed.

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TUPAF052

Effects of Electrostatic Septum Alignment on Particle Loss During Slow Extraction at CERN SPS

alignment, extraction, operation, septum

826

J. Prieto, Y. Dutheil, M.A. Fraser, B. Goddard, V. Kain, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland
M.A. Kagan
SLAC, Menlo Park, California, USA

Slow extraction is an intrinsically lossy process that splits the beam with an electrostatic septum (ES), employing a thin-wire array to delimit the high electric field region that deflects the beam into the extraction channel. At CERN's Super Proton Synchrotron (SPS) the ES is over 16 m long and composed of 5 separate units containing separate wire-arrays that can be moved independently. The tanks are all mounted on a single support structure that can move the ensemble coherently. As a result, the large number of positional degrees of freedom complicates the alignment procedure in operation. Obtaining and maintaining accurate alignment of the ES with the beam is therefore crucial for minimising beam loss. In this paper, we investigate the alignment procedure for different operational scenarios using particle tracking simulations to understand the beam loss along the extraction straight as a function of the relative positions of each of the 5 separate ES units. An important aspect of the study was to understand the required alignment tolerance to achieve optimum extraction efficiency for a given configuration of wire-array thicknesses.

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TUPAF053

Optimization of Diffuser (Pre-Scatterer) Configurations for Slow Extraction Loss Reduction at Electrostatic Septa

septum, scattering, extraction, proton

830

B. Goddard, B. Balhan, J.C.C.M. Borburgh, M.A. Fraser, L.O. Jorat, V. Kain, C. Lolliot, L.S. Stoel, P. Van Trappen, F.M. Velotti
CERN, Geneva, Switzerland
D. Barna
Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary
V.P. Nagaslaev
Fermilab, Batavia, Illinois, USA

Uncontrolled beam loss at the electrostatic septum is a performance limit for several existing or planned high power hadron accelerators delivering slow-extracted spills to fixed targets. A passive diffuser, or pre-scatterer, in a suitable configuration has been shown to reduce such beamloss significantly, with the actual gain factor depending on the parameters and details of the extraction process and hardware. In this paper, the optimization of diffuser configurations is investigated for a range of beam energies and extraction conditions, and the sensitivity to the available parameters explored via simulation results. The advantages and limitations of the diffuser are discussed and conclusions drawn concerning the specific case studies of the 8 GeV Fermilab debuncher ring and 400 GeV CERN SPS.

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TUPAF054

Slow Extraction Efficiency Measurements at the CERN SPS

extraction, proton, operation, septum

834

M.A. Fraser, K. Cornelis, L.S. Esposito, B. Goddard, V. Kain, F. Roncarolo, L.S. Stoel, F.M. Velotti
CERN, Geneva, Switzerland

The high efficiency of most slow extraction systems makes quantifying the exact amount of beam lost in the process extremely challenging. This is compounded by the lack of time structure in the extracted beam, as is typically required by the high-energy physics experiments, and the difficulty in accurately calibrating D.C. intensity monitors in the extraction line at count rates of ~ 10¹³ Hz. As a result, it is common for the extraction inefficiency to be measured by calibrating the beam loss signal induced by the slow extraction process itself. In this paper, measurements of the extraction efficiency performed at the CERN Super Proton Synchrotron for the third-integer resonant slow extraction of 400 GeV protons over recent years will be presented and compared to expectation from simulation. The technique employed will be discussed along with its limitations and an outlook towards a future online extraction efficiency monitoring system will be given.

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TUPAF055

Progress Toward a Dynamic Extraction Bump for Slow Extraction in the CERN SPS

extraction, alignment, septum, closed-orbit

838

L.S. Stoel, M. Benedikt, M.A. Fraser, B. Goddard, J. Prieto, F.M. Velotti
CERN, Geneva, Switzerland

The possibility of reducing the angular spread of slow extracted particles with a time-dependent extraction bump at the CERN Super Proton Synchrotron (SPS) is under investigation. In order to create this so-called dynamic bump, two orthogonal knobs were designed to enable independent movements of the beam in position and angle at the upstream end of the electrostatic extraction septum (ES). With the present slow extraction scheme, simulations show that the use of a dynamic bump can reduce the angular spread at the ES by roughly a factor two and reduce beam loss on the ES. A reduction in the angular spread is also a prerequisite to exploit the full potential of other loss reduction techniques being considered for implementation at the SPS, like the active or passive diffusers planned for installation upstream of the ES in 2018. In this paper, the simulated loss reduction with a dynamic bump alone or in combination with other loss reduction techniques will be assessed, the first beam-based tests of the dynamic bump presented, the details of its implementation examined and its potential for future operation at the SPS discussed.

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TUPAF061

Use of a Massless Septum to Increase Slow-Extraction Efficiency

septum, extraction, sextupole, resonance

862

K. Brunner, M.A. Fraser, B. Goddard, L.S. Stoel, C. Wiesner
CERN, Geneva, Switzerland
D. Barna
Wigner Research Centre for Physics, Institute for Particle and Nuclear Physics, Budapest, Hungary

The Super Proton Synchrotron (SPS) at CERN provides slow-extracted beam for Fixed Target experiments in the North Area. For the higher extracted beam intensities requested by future experimental proposals, beam-loss induced activation will be one of the limiting factors for the availability of such a facility. In this paper, we present and discuss the concept of using a massless septum magnet to increase the extraction efficiency and decrease losses caused by protons scattering on the electrostatic-septa wires.

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TUPAF066

Transverse Dynamics and Software Integration of the ESS Low Energy Beam Transport

solenoid, MMI, ion-source, proton

882

N. Milas, K.S. Louisy, D.C. Plostinar
ESS, Lund, Sweden

The first part of the ESS linac, also called front-end, comprising the Ion Source and the Low Energy Beam Transport (LEBT) section, will be installed and commissioned in 2018. The LEBT is used to focus and correct the proton beam trajectory and clean the head and tail of the proton pulse from the flat top before entering the RFQ. During the ion source and LEBT commissioning a full beam characterization at the RFQ entrance interface is planned. It is thus important to have an application in the control room able to display quantities measured by the diagnostic devices and also to quickly run a simulation including not only centre of mass dynamics but also envelope. This paper presents the efforts in modelling the LEBT elements, as accurately as possible, and implementing the dynamics calculation and integration with diagnostics tools. The final result is a Java FX GUI based on the OpenXAL library.

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TUPAF073

Simulation of Integrable Synchrotron with Space-charge and Chromatic Tune-shifts

lattice, space-charge, optics, synchrotron

894

J.S. Eldred, A. Valishev
Fermilab, Batavia, Illinois, USA

We present a nonlinear rapid-cycling synchrotron designed as a high-intensity replacement of the Fermilab Booster. The design incorporates integrable optics, an innovation in particle accelerator design that enables strong nonlinear focusing without generating parametric resonances. We use the Synergia space-charge tracking code to demonstrate the stability of a beam in this lattice with a space-charge tune-shift up to 0.4 and a rms momentum spread up to 0.4\%. We demonstrate the benefit of increased lattice periodicity.

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TUPAF079

Scaled Alvarez-Cavity Model Investigations for the UNILAC Upgrade

DTL, cavity, alignment, pick-up

916

M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, M. Vossberg
GSI, Darmstadt, Germany
A. Seibel
IAP, Frankfurt am Main, Germany

The 1:3 scaled aluminum model of an Alvarez-type cavity with 10 gaps was used for comparison of simulation with measurement for the frequency and the electric field on axis. The scaled frequency is 325.224 MHz and an Alvarez cavity has a small frequency tuning range. With this scaled model it was possible to apply different stem configurations for each drift tube to damp parasitic modes and to increase the field stability. The new drift tubes have an optimized free-formed profile on the end plates in order to increase the shunt impedance. In special the assembly, positioning and alignment of the drift tubes can be tested and the frequency change can be investigated in this respect.

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TUPAF080

Final Design of the FoS Alvarez-Cavity-Section for the Upgraded UNILAC

cavity, DTL, quadrupole, operation

920

M. Heilmann, X. Du, L. Groening, M. Kaiser, S. Mickat, C. Mühle, A. Rubin, V. Srinivasan
GSI, Darmstadt, Germany
A. Seibel
IAP, Frankfurt am Main, Germany

The final design describes the First-of-Series (FoS) Alvarez-Cavity-section of the first tank being part of the new post-stripper DTL of the UNILAC. The FoS-cavity has an input energy of 1.358 MeV/u with 11 drift tubes (including quadrupole singlets) in a total length of 1.9 m and a diameter of 2 m with an operation frequency of 10⁸.4 MHz. The drift tubes will have a new shape profile at the end plates. The single layered quadruple singlets inside the drift tubes are pulsed with 10 Hz and will have a maximum field gradient of 51 T/m. The new drift tube design combines the new shape profile with the transverse and longitudinal installation space of the magnet. The FoS Alvarez-cavity will be part of the first section of the new Alvarez DTL. It shall be operated at nominal RF- and magnetic fields prior to procurement of the series.

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TUPAF086

Adaption of the HSI -RFQ Rf-Properties to an Improved Beam Dynamics Layout

rfq, operation, linac, resonance

938

M. Vossberg, L. Groening, S. Mickat, H. Vormann, C. Xiao
GSI, Darmstadt, Germany
V. Bencini, J.M. Garland, J.-B. Lallement, A.M. Lombardi
CERN, Geneva, Switzerland

The GSI accelerator facility comprising the linear accelerator UNILAC and the synchrotron SIS18 will be used in future mainly as the injector for the Facility for Anti-Proton and Ion Research (FAIR) being under construction. FAIR requires high beam brilliance and the UNILAC's RFQ electrodes must be upgraded with respect to their beam dynamics design. The new layout is currently being conducted at CERN with the aim of adjusting the electrode voltage according to the design voltage of 123 kV. CST simulations performed at GSI assure that the resonance frequency with the new electrode geometry is recuperated through corrections of the carrier rings. Simulations on the frequency dependence of the rings shapes and their impact on the voltage distribution along the RFQ are presented.

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TUPAF087

A Two-Stage Splitring-RFQ for High Current Ion Beams at Low Frequencies

rfq, impedance, acceleration, resonance

941

M. Baschke, H. Podlech, A. Schempp
IAP, Frankfurt am Main, Germany

Funding: HIC for FAIR, BMBF Contr. No. 05P15RFRBA
For several accelerator projects RFQs are the first stage of acceleration. To reach high intensities a new Splitring-RFQ is investigated. Not only a high current and high beam quality/brilliance should be achieved, also a good tuning flexibility and comfort for maintenance are part of the study. The RFQ will consist of two stages with 27 MHz and 54 MHz to accelerate ions with an A/q of 60 up to energies of 200 keV/u. RF simulations with CST MWS have been performed to obtain the quality factor, shunt impedance and voltage distribution as well as tuning possibilities. The results and the status of the project will be presented.

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TUPAF089

Initial Measurements on a New 10⁸ MHz 4-Rod CW RFQ Prototype for the HLI at GSI

rfq, dipole, linac, resonance

946

D. Koser, K. Kümpel, H. Podlech
IAP, Frankfurt am Main, Germany
P. Gerhard
GSI, Darmstadt, Germany
O.K. Kester
TRIUMF, Vancouver, Canada

Funding: Work supported by BMBF Contr. No. 05P15RFBA and HIC for FAIR
The High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, is one of the two injector linacs for the Universal Linear Accelerator (UNILAC) and is also planned to serve as dedicated injector for a proposed superconducting CW linac for heavy element research. Within the scope of an intended CW upgrade of the HLI front end, a replacement for the existing 4-rod RFQ is desirable since its stable operation and performance is severely impeded by mechanical vibrations of the electrodes and a high thermal sensitivity*. With the aim of suppressing mechanical vibrations and providing efficient cooling considering high power CW operation, a completely new and improved 4-rod design was developed** with a focus on structural mechanical simulations using ANSYS. In order to validate the simulated RF performance, thermal behavior and structural mechanical characteristics, a 6-stem prototype was manufactured***. Initial low power RF measurements and basic piezo actuated mechanical investigations were done and the anticipated properties could be confirmed prior to planned high power RF tests and further mechanical vibration studies.
* D. Koser et al., THPIK021, Proc. of IPAC2017
** D. Koser et al., MOPOY020, Proc. of IPAC2016
*** D. Koser et al., TUPLR057, Proc. of LINAC2016

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TUPAF090

Measurements of the MYRRHA-RFQ at the IAP Frankfurt

rfq, dipole, controls, resonance

949

K. Kümpel, D. Koser, S. Lamprecht, N.F. Petry, H. Podlech, A. Schempp, D. Strecker
IAP, Frankfurt am Main, Germany
A. Bechtold
NTG Neue Technologien GmbH & Co KG, Gelnhausen, Germany
C. Zhang
GSI, Darmstadt, Germany

Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE)
The MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) Project is a planned accelerator driven system (ADS) which aims to demonstrate the feasibility of large scale transmutation. The first RF structure of the 600 MeV MYRRHA Linac will be a 176.1 MHz 4-Rod RFQ that will accelerate up to 4 mA protons in cw operation from 30 keV up to 1.5 MeV. The voltage along the approximately 4 m long electrodes has been chosen to 44 kV which limits the RF losses to about 25 kW/m. During the design of the structure a new method of dipole compensation has been applied. This paper describes the status of the RFQ and shows the results of the measurements done at IAP Frankfurt such as dipole and flatness measurement, vacuum tests and power tests up to 11 kW.

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TUPAK007

Simulation of Surface Muon Beamline, Ultra-Slow Muon Production and Extraction for the J-PARC g-2/EDM Experiment

target, experiment, laser, proton

970

M. Otani, N. Kawamura, T. Mibe, T. Yamazaki
KEK, Tsukuba, Japan
K. Ishida
RIKEN Nishina Center, Wako, Japan
G. Marshall
TRIUMF, Vancouver, Canada

The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1 ppm to cast light on beyond standard model in elementary particle physics. The experiment utilizes a brand new muon beam line in J-PARC (H line), which is designed to have large acceptance to supply an intense muon beam. The surface muons are injected into a silica aerogel target to generate bound state of muon and electron (muonium). Then the muoniums are ionized by lasers and ultra slow (30 meV) muons (USM) are generated. The USM's are extracted by electro-static lens and injected to a muon linac. In this poster, simulation for optics of the surface muon beamline, muonium production and extraction by the electro-static lens, and the estimation of the USM's intensity are presented.

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TUPAK008

Longitudinal Bunch Size Measurements with an RF Deflector at J-PARC LINAC

radio-frequency, linac, rfq, DTL

974

M. Otani, K. Futatsukawa
KEK, Tsukuba, Japan
K. Hirano, A. Miura
JAEA/J-PARC, Tokai-mura, Japan
Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan
T. Maruta
FRIB, East Lansing, USA

Measurement of the longitudinal bunch size is important for the stable beam operation. Especially in a medium energy beam transport (MEBT) located after a radio-frequency quadrupole in J-PARC, it is necessary to measure the bunch size with minimum set of equipment to avoid subsequent emittance growth due to space charge. We had proposed a longitudinal size measurement with an rf deflector normally used for deflecting theμbunch; phase spread is migrated to spatial one if the reference particle arrives at the deflector when the voltage is rising in time and is zero. Then a buncher cavity located upstream of the deflector is utilized to scan the phase spread to measure the longitudinal beam parameters. In this poster, recent measurement results are presented.

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TUPAK009

Muon Profile Measurement After Acceleration With a Radio-Frequency Quadrupole Linac

experiment, rfq, linac, positron

977

M. Otani, Y. Fukao, K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, T. Yamazaki
KEK, Tsukuba, Japan
S. Bae, H. Choi, S. Choi, B. Kim, H.S. Ko
SNU, Seoul, Republic of Korea
K. Hasegawa, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
T. Iijima, Y. Sue
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan
H. Iinuma, Y. Nakazawa
Ibaraki University, Ibaraki, Japan
K. Ishida
RIKEN Nishina Center, Wako, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
S. Li
The University of Tokyo, Graduate School of Science, Tokyo, Japan
G.P. Razuvaev
Budker INP & NSU, Novosibirsk, Russia
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
E. Won
Korea University, Seoul, Republic of Korea

Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784.
The E34 experiment aims to measure muon anomalous magnetic moment with a precision of 0.1ppm. The experiment utilizes low emittance muon beam with a muon linac to sweep out beam related uncertainties, which limit the g-2 precision in past experiments. A beam matching with precise beam measurements is required to avoid substantial emittance growth and satisfy the experimental requirement on the beam emittance of around 1.5 pi mm mrad. We conduct profile measurement of muon after acceleration with a radio-frequency quadrupole (RFQ) on December 2017 following a first muon acceleration experiment on October. In the experiment of profile measurement, epi-thermal negative muonium ions are generated by injecting surface muons to a thin metal foil. The muonium ions are accelerated to 5 keV. by an electro-static lens and accelerated to 90 keV by the RFQ. Then the muonium ions are transported to a profile detector consisting of a micro-channel plate and a ccd camera via a quadrupole pair and a bending magnet. In this poster, the experimental result and comparison to the simulation are reported.

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TUPAK013

Geant4 Simulation of Radiation Effect on the Deflector of Extraction System in HUST SCC250

septum, proton, neutron, radiation

990

S. Hu, K. Fan, L.X.F. Li, Z.Y. Mei, Z.J. Zeng, L.G. Zhang
HUST, Wuhan, People's Republic of China

China has payed extensive attention to the development of proton therapy in recent years. When design a compact, high energy superconducting cyclotron for proton therapy， radiation effect induced by beam losses is a crucial consideration. Since the proton beam is extracted out of HUST SCC250 by electrostatic deflectors, the fierce interaction between proton beam and the deflector septum is the main cause of beam losses, which will bring about radiation effect leading to activation and coil quench. This paper presents simulation results of radiation effect by utilizing Geant4 Monte Carlo code. The energy depositions of proton beam in various septum materials are compared. Meanwhile, the yields, the ener-gy and angular distributions of secondary particles are investigated. Those simulation results based on radiation effect will provide us with valuable implications for the design of this superconducting cyclotron.

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TUPAK017

Abandoned Proton Beam Separation Design at MOMENT

proton, target, separation-scheme, secondary-beams

1001

C. Meng, H.T. Jing, Y.P. Song, J.Y. Tang, H. Wang
IHEP, Beijing, People's Republic of China

Funding: The National Natural Science Foundation of China under Grants 11575217
MOMENT (MuOn-decay MEdium baseline NeuTrino beam facility) is an accelerator-based neutrino beam facility using neutrino from muon decays. The proton driver is a continuous-wave proton linac of 1.5 GeV and 10 mA, which means an extremely high beam power of 15 MW. After bombarding the target, the abandoned proton beam power is very high and should be separate from target station carefully. Because of the energy is not very high and the layout of following transport line isn't linear, we should design special separation line for high momentum proton beam. In this paper the design of separation scheme at MOMENT will be proposed and discussed.

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TUPAL009

Studying a Prototype of Dual-beam Drift Tube Linac

DTL, cavity, rfq, acceleration

1020

T. He, L. Lu, W. Ma, L.P. Sun, C.C. Xing, X.B. Xu, L. Yang
IMP/CAS, Lanzhou, People's Republic of China

For generating high-intensity ion beams from linear ac-celerators, a multi-beam acceleration method which in-volves multiple accelerating beams to suppress the defo-cusing force from space charge effects, then integrating these beams by a beam funneling system, has been pro-posed. An Inter-digital H-mode (IH) two-beam type radio frequency quadrupole (RFQ) with accelerating 108mA (54mA/channel×2) carbon ion from 5 to 60 keV/ u and an IH four-beam RFQ with accelerating 160.8mA (40.2mA/channel×4) carbon ion from 3.6 to 41.6 keV/u had been successfully designed for low energy heavy ion acceleration [1]. In order to demonstrate that an IH dual-beam drift tube linac (DB-DTL) is suitable for high-intensity heavy ion beam acceleration in middle energy region, we has been developing a DB-DTL prototype by using three dimensional electromagnetic CST MicroWave Studio (MWS) and using particles tracking Pi Mode Linac Orbit Calculation (PiMLOC) [2-3]. According to the simulation results, the beam dynamics design and elec-tromagnetic design will be presented in this paper.
* Shota. Iketa et al., Nucl. Instr. and Meth. in Phys. Res. B.239-243 (2017).

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TUPAL035

3D Beam Dynamics Modeling of MEBT for the New LANSCE RFQ Injector

emittance, rfq, quadrupole, proton

1081

S.S. Kurennoy
LANL, Los Alamos, New Mexico, USA

The new RFQ-based proton injector at LANSCE requires a specialized medium-energy beam transfer (MEBT) after the RFQ at 750 keV due to a following long (~3 m) existing common transfer line that also serves for transporting negative-ion beams to the DTL entrance. The horizontal space for MEBT elements is limited because two beam lines merge at 18-degree angle. The MEBT design developed with envelope codes includes two compact quarter-wave RF bunchers and four short quadrupoles with steerers, all within the length of about 1 m. The beam size in the MEBT is large, comparable to the beam-pipe aperture, hence non-linear 3D field effects at large radii become important. Using CST Studio codes, we calculate buncher RF fields and quadrupole magnetic fields and use them to perform particle-in-cell beam dynamics modeling of MEBT with realistic beam distributions from the RFQ. Our results indicate a significant emittance growth not predicted by standard beam dynamics codes. Its origin was traced mainly to the quadrupole edge fields. Quadrupole design modifications are proposed to improve the MEBT performance.

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TUPAL036

Slow Extraction Techniques at the Marburg Ion-Beam Therapy Centre

extraction, synchrotron, controls, resonance

1084

C. Krantz, T. Fischer, Th. Haberer, B. Kroeck, U. Scheeler, A. Weber, M. Witt
MIT, Marburg, Germany
R. Cee, F. Faber, E. Feldmeier, M. Galonska, Th. Haberer, A. Peters, S. Scheloske, C. Schömers
HIT, Heidelberg, Germany
F. Faber
Technische Universität Darmstadt (TU Darmstadt, RMR), Darmstadt, Germany

The Marburg Ion-Beam Therapy Centre offers hadron therapy using proton and carbon beams. The accelerator is based on a 65-m ion synchrotron by Danfysik/Siemens Healthcare. Beam extraction from the synchrotron is driven by a transverse RF knock-out (KO) system featuring Dynamic Intensity Control (DIC) of the spill. DIC allows modulation of the extraction rate by factors up to 30 on millisecond time scales. A fast response of the system to the variable intensity set-point can be obtained by careful adjustment of the RF-KO spectrum relative to the machine tune. Tracking simulations of the extraction phase have been conducted to refine that behaviour. Presently, we investigate how fast machine tune shifts, induced by an air-core quadrupole lens, can be used as a way to further improve the spill quality.

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TUPAL043

Simulations of the Electron Column in IOTA

electron, plasma, proton, space-charge

1103

B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay
Northern Illinois Univerity, DeKalb, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
C.S. Park
Korea University Sejong Campus, Sejong, Republic of Korea
G. Penn
LBNL, Berkeley, California, USA
V.D. Shiltsev, G. Stancari
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Contract Nos. DE-AC02-07CH11359 and DE-AC02-05CH1123 and General Accelerator Research and Development Program
Future high current proton accelerators will need to minimize beam loss due to space-charge in order to achieve safe operation while achieving the desired physics goals. One method of space-charge compensation to be tested at the Integrable Optics Test Accelerator (IOTA) at Fermilab is the Electron Column. The concept for this device is to allow a circulating beam to ionize a small region of relatively high pressure residual gas, while using electric and magnetic fields to confine and shape the resulting plasma electrons. If the profile of the electrons is matched to the beam profile transversely and longitudinally, the electrons should counteract the space-charge force of the proton beam. Simulations of the IOTA proton beam circulating through the Electron Column have been performed, with the evolution of the electron plasma and its effect on the beam studied.

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TUPAL056

High Order Image Terms and Harmonic Closed Orbits at the ISIS Synchrotron

closed-orbit, resonance, space-charge, vacuum

1140

B.G. Pine, C.M. Warsop
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the spallation neutron source at Rutherford Appleton Laboratory in the UK. Protons are accelerated from 70 to 800 MeV in a 50 Hz rapid cycling synchrotron. Due to the intense beam, space charge forces are high during the first part of the acceleration cycle. The vacuum vessel in the synchrotron has a rectangular shape where the apertures are conformal to the design beam envelopes. At high intensities image forces interact with the beam, especially when the closed orbit is large. An analysis of image forces has been made and used to classify higher order image terms. These have been identified using simulations of round beams in rectangular vacuum vessels. The higher order image terms from harmonic closed orbits have been used with single particle resonance theory, taking account of the coherent nature of the beam response. Several predictions of beam resonance have been made. A simulation study has been carried out using a smooth focusing lattice and uniform density beams. Resonant beam behaviour has been observed and explained by the proposed theory.

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TUPAL058

Studies for Major ISIS Upgrades via Conventional RCS and Accumulator Ring Designs

injection, lattice, space-charge, emittance

1148

C.M. Warsop, D.J. Adams, H.V. Cavanagh, P.T. Griffin-Hicks, B. Jones, B.G. Pine, R.E. Williamson
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom

ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK, which provides 0.2 MW of beam power via a 50 Hz, 800 MeV proton RCS. Detailed studies are now under way to find the optimal configuration for a next generation, short pulsed neutron source that will define a major ISIS upgrade in ~2031. Accelerator configurations being considered for the MW beam powers required include designs exploiting FFAG rings as well as conventional accumulator and synchrotron rings. This paper describes work exploring the latter, conventional options, but includes the possibility of pushing further toward intensity limits to reduce facility costs. The scope of planned studies is summarised, looking at optimal exploitation of existing ISIS infrastructure, and incorporating results from recent target studies and user consultations. Results from initial baseline studies for an accumulator ring and RCS located in the existing ISIS synchrotron hall are presented. Injection scheme, foil limits, longitudinal and transverse beam dynamics optimization with related beam loss and activation are outlined, as are results from detailed 3D PIC simulations.

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TUPAL062

Recent Developments for Cyclotron Extraction Foils at TRIUMF

electron, extraction, cyclotron, TRIUMF

1159

Y. Bylinskii, R.A. Baartman, P.E. Dirksen, Y.-N. Rao, V.A. Verzilov
TRIUMF, Vancouver, Canada

Funding: Funded under a contribution agreement with NRC (National Research Council Canada).
The TRIUMF 500 MeV H− cyclotron employs stripping foils to extract multiple beams for different experimental programs. The upgrades in foil material and foil holders lead to significant improvements in beam quality and foil life time, as well as reduction of Be-7 contamination originated in the foils. Thus, an accumulated beam charge extracted with a single foil increased from ~60 mA·hours to more than 500 mA·hours. A key role that lead to these advances was an understanding of the foil heating mechanism, major contribution to which is paid by the power deposition from electrons stripped by the foil. To further diminish this effect, we recently introduced a foil tilt from the vertical orientation that allows stripped electrons fast escape from the foil, well before losing their original momentum through the heat deposition. Other improvements were related to operational issues. Introduction of a "combo" foil consisting of wide portion and thin wire allowed both high and low intensity beam extraction without foils sacrifice. Deploying a wedge foil for extraction at 100 MeV helped reduction of beam intensity instabilities caused by beam vertical size and position fluctuations.

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TUPAL068

The Development of a Nw Fast Harmonic Kicker for the JLEIC Circulator Cooling Ring

kicker, cavity, emittance, electron

1171

G.-T. Park, F. Fors, J. Guo, R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the first half-scale, 5 harmonic kicker cavity prototyping * for the JLEIC's CCR/ERL electron cooler and the beam dynamic simulation study of the 10-turn CCR **. The optimized circulation cooling turns has been changed to 11 and only 5 odd-harmonic modes from 86.6 MHz to 779.4 MHz plus a DC bias are needed for the harmonic RF kicker system. The new cavity design including the electromagnetic and thermal cooling optimization and its 11 turns beam bunch tracking simulation with the new numerology of RF deflecting voltages will be presented. Further design specifications for its RF harmonic drive and the broadband RF window, coupler and circulator component will be given for handling 5 kW of total RF power.
* Y, Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 122001 (2016).
** Y. Huang, H. Wang et al., Physical Review Accelerators and Beams 19, 084201 (2016).

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TUPAL069

Experimental Demonstration of Ion Beam Cooling with Pulsed Electron Beam

electron, experiment, synchrotron, data-analysis

1174

Y. Zhang, A. Hutton, K. Jordan, T. Powers, R.A. Rimmer, M. F. Spata, H. Wang, S. Wang, H. Zhang
JLab, Newport News, Virginia, USA
J. Li, X.M. Ma, L.J. Mao, M.T. Tang, J.C. Yang, X.D. Yang, H. Zhao, H.W. Zhao
IMP/CAS, Lanzhou, People's Republic of China

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Cooling ion beams at high energy is presently considered for several ion colliders, in order to achieve high luminosities by enabling a significant reduction of emittance of hadron beams. Electron beam at cooling channel in a few to tens MeV can be accelerated by a RF/SRF linac, and thus using bunched electrons to cool bunched ions. To study such cooling process, the DC electron gun of EC35 cooler at the storage ring CSRm, IMP was modified by pulsing the grid voltage. A 0.07-3.5 micro-second pulse length with a repetition frequency of less than 250 kHz and synchronized with the ion revolution frequency was obtained. The first experimental demonstration of cooling of a coasting and bunched ion beam by a pulsed electron beam was carried out. Data analysis indicates the bunch length shrinkage and the momentum spread reduction of bunched 12C+6 ion beam as evidence of cooling. A longitudinal grouping effect of the coasting ion beam by the electron pulses has also been observed*. In this paper, we will present experimental results and comparison to the simulation modelling, particularly on the bunched electron cooling data after carefully analyzing the beam diagnostic signals.
* L.J. Mao et al., Experimental Demonstration of Electron Cooling with Bunched Electron Beam, TUP15, Proceedings of COOL2017, Bonn, Germany

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TUPAL075

Mechanical Design and Error Analysis of a 325 MHz IH-DTL Test Cavity

DTL, alignment, cavity, linac

1186

R. Tang, C.T. Du, X. Guan, K.D. Man, C.-X. Tang, X.W. Wang, Q.Z. Xing, S.X. Zheng
TUB, Beijing, People's Republic of China
J. Li
NUCTECH, Beijing, People's Republic of China

A 325 MHz interdigital H-mode drift tube linac (IH-DTL) test cavity with a modified KONUS beam dynamics is under fabrication at Tsinghua University. The inner diameter of the tank increases from 196.8 to 232.6 mm. The mechanical design is considered carefully because of its small geometry. A three-piece design has been adopted in the mechanical design. The error analysis is carried out to determine the error requirement of machining and alignment. The details of mechanical design and error analysis is presented.

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TUPAL076

Result of the First Muon Acceleration with Radio Frequency Quadrupole

rfq, acceleration, experiment, target

1190

R. Kitamura
University of Tokyo, Tokyo, Japan
S. Bae, B. Kim
SNU, Seoul, Republic of Korea
Y. Fukao, K. Futatsukawa, N. Kawamura, T. Mibe, Y. Miyake, M. Otani, T. Yamazaki
KEK, Tsukuba, Japan
K. Hasegawa, Y. Kondo, T. Morishita
JAEA/J-PARC, Tokai-mura, Japan
H. Iinuma, Y. Nakazawa
Ibaraki University, Ibaraki, Japan
G.P. Razuvaev
Budker INP & NSU, Novosibirsk, Russia
N. Saito
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Y. Sue
Nagoya University, Graduate School of Science, Chikusa-ku, Nagoya, Japan

Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784.
J-PARC E34 experiment aims to measure the muon g-2/EDM precisely with novel techniques including the muon linear accelerator. Slow muon source by the metal foil method in order to cool the muon beam has been developed for the muon acceleration test with RF accelerator, because the muon beam derived from the proton driver was the tertiary beam and has a large emittance. The first verification test of the muon acceleration with RFQ was carried out at the muon test beam line of J-PARC MLF in October 2017. The incident surface muons were decelerated by the thin metal foil target and produced the negative muonium ions (Mu-), which is the bound stat of a positive muon and two electrons. After Mu- were extracted by a electrostatic accelerator as the injector of the RFQ, they were accelerated with RFQ to 88.6 keV. The accelerated Mu- were identified by the momentum selection with the bending magnet after the RFQ, and the measurement of the Time-Of-Flight. Accelerated Mu- were easily distinguished from penetrated positive muons by the difference of the polarity. The latest analysis result of the world's first muon acceleration with RFQ will be reported in this paper.

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TUPAL077

2D-3D PIC Code Benchmarking/Anchoring Comparisons For a Novel RFQ/RFI LINAC Design

rfq, space-charge, linac, experiment

1194

S.J. Smith, S. Biedron, A. M. N. Elfrgani, E. Schamiloglu
University of New Mexico, Albuquerque, USA
M.S. Curtin, B. Hartman, T. Pressnall, D.A. Swenson
Ion Linac Systems, Inc., Albuquerque, USA
K. Kaneta
CICS, Tokyo, Japan

Funding: *The study at the University of New Mexico was supported in part by DARPA Grant N66001-16-1-4042 and gift to the University of New Mexico Foundation by ILS.
In this study, comparisons are made between several particle dynamics codes (namely CST Particle Studio, GPT, and upgraded PARMILA codes) in order to benchmark them. The structure used for the simulations is a novel 200 MHz, 2.5 MeV, CW RFQ/RFI LINAC designed by Ion Linac Systems (ILS). The structure design and parameters are provided, simulation techniques are explained, and results from all three code families are presented. These results are then compared with each other, identifying similarities and differences. Numerous parameters for comparison are used, including the transmission efficiency, Q-factor, E-field on axis, and beam properties. Preliminary anchoring between modeling and simulation performance predictions and experimental measurements will be provided.

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TUZGBF5

KlyLac Prototyping for Borehole Logging

klystron, linac, cavity, feedback

1244

A.V. Smirnov, R.B. Agustsson, M.A. Harrison, A.Y. Murokh, A.Yu. Smirnov
RadiaBeam Systems, Santa Monica, California, USA
S. Boucher, T.J. Campese, K.J. Hoyt
RadiaBeam, Los Angeles, California, USA
E.A. Savin
MEPhI, Moscow, Russia
A.A. Zavadtsev
Nano, Moscow, Russia

Funding: Work supported by the U.S. Department of Energy (award No. DE-SC0015721)
Linac-based system for borehole logging exploits KlyLac approach combing klystron and linac sharing the same electron beam, vacuum volume, and RF network enabling self-oscillation due to a positive feedback. The KlyLac prototype design tailors delivering ~1 MeV electrons in a linac section using part of the beam injected from a sheet beam klystron (SBK). The linac part is based on a very robust, high group velocity, cm-wave, and a standing wave accelerating structure of a 'cross-pin' type supplied by a sampler. The SBK part features a permanent magnet solenoid focusing, relatively low voltage, and high aspect ratio beam. The main SBK characteristics (perveance, power, and efficiency) are expected to be similar to that for a magnetron.

Slides TUZGBF5 [3.280 MB]

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TUPMF005

Simulation of Inverse Compton Scattering and Its Implications on the Scattered Linewidth

electron, emittance, laser, scattering

1254

N. Ranjan, B. Terzić
ODU, Norfolk, Virginia, USA
I. Drebot, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano, Italy
G.A. Krafft
JLab, Newport News, Virginia, USA
V. Petrillo
Universita' degli Studi di Milano & INFN, Milano, Italy

Funding: This paper is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Compton scattering, though first described some one hundred years ago, has recently experienced a surge of interest due to the search for energy sources that are capable of yielding low emission bandwidths. In particular, the desire for hard x-rays with energies greater than 10 keV has led to increased study of inverse Compton sources. The rise in interest concerning inverse Compton sources has increased the need for efficient models that properly quantify the behavior of scattered radiation given a set of interaction parameters. The current, state-of-the-art, simulations rely of Monte Carlo-based methods, which may fail to properly model collisions of bunches in low-probability regions of the spectrum. Furthermore, the random sampling of the simulations may lead to inordinately high runtimes. Our methods can properly model behaviors exhibited by the collisions by integrating over the emissions of the electrons in the bunch in a lessened amount of time. Analytical simulations of Gaussian laser beams closely verify the behavior predicted by an analytically derived scaling law describing bandwidth of scattered radiation.
Current affiliation of primary author (Nalin Ranjan) is Princess Anne High, Virginia Beach, VA 23452, USA.

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TUPMF012

Determination of the Ground Motion Orbit Amplification Factors Dependence on the Frequency for the APS Upgrade Storage Ring

ground-motion, factory, lattice, storage-ring

1272

V. Sajaev, C.A. Preissner
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is pursuing an upgrade to the storage ring that will provide electron beam with extremely low emittance. To allow users to take advantage of this small beam size, the beam orbit motion has to be kept stable to within a fraction of the beam size, which translates to sub-micron orbit stability requirement. Ground motion provides significant contribution to the overall expected beam motion, especially at lower frequencies where the ground motion has larger amplitudes. At the same time, the lattice amplification factors reduce when the ground motion becomes coherent at low frequencies. In this paper, we will present simulation of the lattice amplification factor dependence on the ground motion coherence length and show results of the ground motion coherence measurements at APS. After that, we will determine the lattice amplification factors dependence on the ground motion frequency, that can be used to calculate the expected effect of the ground motion on the orbit stability.

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TUPMF016

Application of SVD Analysis to Deflecting Cavitiy Space Harmonics

cavity, timing, data-analysis, experiment

1283

C. Yao, L. Emery, D. Hui, H. Shang, Y.P. Sun
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Singular value decomposition (SVD) analysis is a powerful tool for identifying different spatial and timing variation patterns in many fields of researches. Recently we applied complex SVD method to space harmonic analysis of a 13-cell defecting cavity that is built and installed in the APS linac injector for beam phase space characterization and emittance exchange experiments. Real and imaginary space harmonics components are extracted from CST simulated data. Fields inside the iris were expressed in analytic forms and produced good agreement. Work is underway to implement the results into elegant simulation model.

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TUPMF018

Simulation Studies of the Helical Superconducting Undulator Installed at APS

multipole, undulator, operation, storage-ring

1290

A. Xiao, V. Sajaev, Y.P. Sun
ANL, Argonne, Illinois, USA

A multi-year project at APS has resulted in construction of a helical superconducting undulator (HSCU) for installation in the ring. Before installation, simulation studies were done to ensure that APS performance will not be compromised. This paper describes the method used for calculating the HSCU's perturbation effects and the simulation results for both calculated and measured field map.
Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

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TUPMF021

Investigation of Options for Damping Trapped IVU Resonances

resonance, impedance, damping, undulator

1296

R.T. Dowd
AS - ANSTO, Clayton, Australia
W.J. Chi, D. Pelz
RFS, Kilsyth, Australia

Trapped resonances have been observed within the three In-Vacuum Undulators (IVUs) insertion devices at the Australian Synchrotron. These resonances can create vertical beam instability if not controlled through transverse feedback systems. Similar resonances have been observed at other synchrotron light sources around the world. Under certain conditions of undulator gap, these resonances can couple quite strongly to the beam, requiring high feedback gain. An investigation of the resonances has been carried out using 3D eigenmode and wakefield simulations to understand the resonances and determine the effectiveness of various schemes for modifying the damping the resonances.

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TUPMF034

Measuring the Electrical Center and Field Flatness of 704 MHz Deflecting Cavity for LEReC with Wire Stretching System

cavity, diagnostics, pick-up, experiment

1320

T. Xin, J.M. Brennan, J.C.B. Brutus, K. Mernick, K.S. Smith, B. P. Xiao, A. Zaltsman
BNL, Upton, Long Island, New York, USA
W. Johnson
SBU, Stony Brook, New York, USA
H. Wang
JLab, Newport News, Virginia, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
704 MHz deflecting cavity was designed for the Low Energy RHIC electron Cooling (LEReC) project. The cavity will serve as a major component in diagnostic line. In LEReC project the requirement on the energy spread of the electron beam is extremely high (better than 10^-4) and the diagnostic system has to to be designed accordingly. The 704 MHz transverse deflecting cavity provides the vertical kick to the beam after it passes through the dispersion dipole so that we can measure the energy spread of the core of the bunch. Traditional way of determining the electrical center of the cavity involves the needle pulling and integration of the signal which is prone to the cumulative error. We present the measurement result from a wire stretching system that is much more efficient and accurate compared to the bead/needle pulling method. Both simulation and experimental results are shown in this paper and the potential in further application is discussed at the end.

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TUPMF048

On-Axis Beam Accumulation Based on a Triple-Frequency RF System for Diffraction-Limited Storage Rings

cavity, injection, accumulation, photon

1359

S.C. Jiang, Z. Duan, G. Xu
IHEP, Beijing, People's Republic of China

Since the multi-bend achromats have been applied to lattice design in the future light source to achieve ultralow emittance, strong sextupoles and concomitant nonlinearities restrict its performance to a certain extent. The empirical understanding is the exclusion of conventional off-axis injection scheme on these light sources. In this paper, we will present a new on-axis beam accumulation scheme, which is based on the triple-frequency RF system. By means of delicate superposition of RF voltage with fundamental and two other harmonic frequencies, a commodious and steady main bucket is able to be formed. The electron bunch from the injector will be kicked into the main bucket on-axis with a reasonable time offset to the circular bunch, and this process may make the minimal disturbance to the experiment users while operating on the top-up mode. The application of this scheme to the High Energy Photon Source (HEPS) will be discussed in the paper, corresponding simulation results are also presented.

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TUPMF053

Longitudinal Impedance Measurement of the Strip-Line Kicker for High Energy Photon Source (HEPS)

impedance, kicker, coupling, distributed

1379

S.K. Tian, J. Chen, Y. Jiao, H. Shi, L. Wang, N. Wang
IHEP, Beijing, People's Republic of China

The High Energy Photon Source (HEPS) is a 6-GeV, kilometer-scale storage ring light source to be built in China. One of the main design challenges of the storage ring is to minimize collective instabilities associated with the impedance of small-aperture vacuum components. In this paper we present beam coupling impedance measurements obtained by the well known coaxial wire method, for the HEPS Strip-Line kicker. The frequency dependent real and imaginary parts of the distributed impedance are obtained from the measured S-parameters.

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TUPMF059

Error Study of HEPS Booster

closed-orbit, booster, multipole, lattice

1398

C. Meng, D. Ji, J.L. Li, Y.M. Peng
IHEP, Beijing, People's Republic of China

The High Energy Photon Source (HEPS) is a 6-GeV, ultralow-emittance light source to be built in China. The injector is composed of a 500-MeV linac and a full energy booster with 1 Hz repetition frequency. The detailed error study of the booster will be presented, including misalignment errors and closed orbit correc-tion, magnetic field errors and power supply errors. The effect of errors on closed orbit, tune, chromaticity and dynamic aperture will be discussed. The dynamic aperture with multipole errors will be presented also.

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TUPMF073

Impedance Optimization of Small Gap Chambers for the High Single Bunch Current Operation at the Undulator Based Light Sources

impedance, lattice, undulator, ECR

1430

Y.-C. Chae
DESY, Hamburg, Germany

In the undulator based light sources the intensity limit of single bunch is often determined by the strong vertical instability caused by the wakefield in the ring, where the undulator itself is large impedance source. The optimization of transition from the large aperture to undulator's small-gap chamber is on-going research topic in an effort to reduce the vertical impedance; at the same time, the demand on single-bunch current is high from the timing-mode x-ray user community. In this paper, after showing the results obtained by exploring the parameter space guided by Stupakov's formula, we propose the linearly-segmented transition which can reduce the impedance down to 60% or less of the original linear taper. The reduction can be utilized either to increase the bunch current substantially or to install a smaller gap chamber without impacting the bunch current limit. For the definite result we considered the transition between two ellipses, namely, (a, b) = (42 mm, 21 mm) and (18 mm, 4 mm) over the length 15-30 cm in beam direction.

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TUPMF076

Temporal X-ray Reconstruction Using Temporal and Spectral Measurements

electron, photon, FEL, laser

1440

F. Christie, J. Rönsch-Schulenburg, M. Vogt
DESY, Hamburg, Germany
Y. Ding, Z. Huang, J. Krzywinski, A.A. Lutman, T.J. Maxwell, D.F. Ratner
SLAC, Menlo Park, California, USA
V. A. Jhalani
CALTECH, Pasadena, California, USA

Transverse deflecting structures (TDS) are widely used in accelerator physics to measure the longitudinal density of particle bunches. When used in combination with a dispersive section, the whole longitudinal phase space density can be imaged. At the Linac Coherent Light Source (LCLS), the installation of such a device downstream of the undulators enables the reconstruction of the X-ray temporal intensity profile by comparing longitudinal phase space distributions with lasing on and lasing off*. However, the resolution of this TDS is limited to around 1 fs rms (root mean square), and therefore, in most cases, it is not possible to resolve single self-amplified spontaneous emission (SASE) spikes within one photon pulse. By combining the intensity spectrum from a high resolution photon spectrometer** and the temporal structure from the TDS, the overall resolution is enhanced, thus allowing the observation of temporal, single SASE spikes. The combined data from the spectrometer and the TDS is analyzed using an iterative algorithm to obtain the actual intensity profile. In this paper, we present the reconstruction algorithm as well as analyzed data obtained from simulations which shows the reliability of this method. Real data will be published at a later stage.
*Y. Ding et al., Phys. Rev. ST AB, 14, 120701, 2011.
**D. Zhu et al., Appl. Phys. Lett., 101, 034103, 2012.

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TUPMF078

Control of FEL Radiation Properties by Tailoring the Seed Pulses

FEL, laser, experiment, electron

1444

V. Grattoni, R.W. Aßmann, J. Bödewadt, I. Hartl, C. Lechner, B. Manschwetus, M.M. Mohammad Kazemi
DESY, Hamburg, Germany
A. Azima, W. Hillert, V. Miltchev, J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Khan, T. Plath
DELTA, Dortmund, Germany

Seeded free-electron lasers (FELs) produce intense, ultrashort and fully coherent X-ray pulses. These seeded FEL pulses depend on the initial seed properties. Therefore, controlling the seed laser allows tailoring the FEL radiation for phase-sensitive experiments. In this contribution, we present detailed simulation studies to characterize the FEL process and to predict the operation performance of seeded pulses. In addition, we show experimental data on the temporal characterization of the seeded FEL pulses performed at the sFLASH experiment in Hamburg.

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TUPMK002

First Tests of the Apple II Undulator for the LOREA Insertion Device and Front End

vacuum, undulator, optics, insertion-device

1488

J. Campmany, L.G.O. Garcia-Orta, J. Marcos, Z. Martí, V. Massana, M. Quispe
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

ALBA synchrotron is currently installing the new beamline LOREA (Low-Energy Ultra-High-Resolution Angular Photoemission for Complex Materials at ALBA). It operates in the range of 10 - 1500 eV with polarized light. To produce the light for the beamline, an Apple II undulator with a period of 125 mm has been chosen. It can operate as an undulator at low energies and as a wiggler at high energies, providing a wide energy range. The device was built by KYMA, delivered on February 2017 and installed in August 2017. We present the magnetic measurements made during SAT as well as the simulations of the influence of the ID in the electron beam dynamics and the first measurements with beam. On the other hand, the high demanding characteristics of the beamline lead to a device providing high power and wide beam in some working modes. This situation has been a challenge for the Front End (FE) thermal load. It has been built by the companies RMP and TVP, and the FE modules have been installed in the tunnel along autumn 2017. We present the Site Acceptance Tests results as well as the technical solutions adopted, especially in terms of mechanical design and used materials.

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TUPMK004

Using Decoherence to Prevent Damage to the Swap-Out Dump for the APS Upgrade

emittance, kicker, electron, storage-ring

1494

M. Borland, J.C. Dooling, R.R. Lindberg, V. Sajaev, A. Xiao
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) is pursuing an upgrade of the storage ring to a hybrid seven-bend-achromat* design, which will operate in swap-out mode. The ultra-low emittance (about 30 pm in both planes) combined with the desire to provide high charge (15 nC) in individual bunches, entails very high energy density in the beam. Simple estimates, confirmed by simulation, indicate that interaction of such a bunch with the dump material will result in localized melting. Over time, it is possible that the beam would drill through the dump and vent the ring vacuum. This would seem to prevent extraction and dumping of bunches as part of swap out, and also suggests that transferring of bunches out of the ring carries significant risk. We devised an idea for using a pre-kicker to cause decoherence of the target bunch emittances, making it safe to extract. Simulations show that the concept works very well.
*L. Farvacque et al., IPAC13, 79 (2013).

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TUPMK005

CSR Shielding Effect in Dogleg and EEX Beamlines

shielding, dipole, experiment, emittance

1498

G. Ha, M.E. Conde, J.G. Power, E.E. Wisniewski
ANL, Argonne, Illinois, USA

Funding: Department of Energy, Office of HEP and BES under Contract No. DE-AC02-06CH11357.
CSR shielding is a well-known CSR suppression scheme which works by cutting off the low frequency CSR radiation. Although the shielding scheme is well known, its effects on the beam has been rarely studied. We investigate the CSR effect on the beam emittance when passing through a dogleg and a double dogleg type EEX beamline. An experimental study is planned at the Argonne Wakefield Accelerator facility where we can generate a 0.1-100 nC electron beam with an energy of 50 MeV and have a double dogleg EEX beamline. Tunable shielding plates are installed at the dipole magnet chambers of the EEX beamline to vary the shielding condition. Transverse and longitudinal phase space measurement systems are prepared to characterize the beam-CSR interaction, and bolometer and interferometry are prepared to characterize CSR. We present simulation results and preliminary experimental results.

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TUPMK006

Sub-fs Electron Bunch Generation Using Emittance Exchange Compressor

emittance, sextupole, cavity, electron

1501

J.M. Seok, M. Chung
UNIST, Ulsan, Republic of Korea
M.E. Conde, J.G. Power
ANL, Argonne, Illinois, USA
G. Ha
PAL, Pohang, Republic of Korea

Sub-fs electron bunch has been pursued in the last decade using several different methods. These methods rely on one of the velocity difference or path length difference to compress a long bunch to sub-fs bunch. Here, we introduce a new method to generate the compression. Emittance Exchange (EEX) beamline makes transverse-to-longitudinal exchange of phase space. In this beamline, a transverse focusing at the upstream introduces a longitudinal compression at the downstream due to the exchange. Since this exchange scheme does not rely on the velocity or the path length differences, it does not require any longitudinal manipulation (e.g. chirp), and it could generate a short bunch with well-controlled nonlinear effects using nonlinear magnets. We present preliminary simulation results of EEX based bunch compression and sub-fs bunch generation.

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TUPMK009

Electron Beam Optics for the ASU Compact XFEL

dipole, FEL, electron, laser

1507

C. Zhang, W.S. Graves, M.R. Holl, L.E. Malin
Arizona State University, Tempe, USA
E.A. Nanni
SLAC, Menlo Park, California, USA

Funding: National Science Foundation Division of Physics (Accelerator Science) award 1632780, award 1231306. DOE grant DE-AC02-76SF00515.
Arizona State University (ASU) is pursuing a new concept for a compact x-ray FEL (CXFEL) as a next phase of compact x-ray light source (CXLS). We describe the electron beam optics design for the ASU compact XFEL. In previous experiments we introduced a grating diffraction method to generate a spatially modulated beam. We plan to combine a telescope imaging system with emittance exchange (EEX) to magnify/demagnify the modulated beam and transfer it from transverse modulation into a longitudinal one to make it an ideal seed for phase-coherent XFEL. The simulation results of the beam line setup will be demonstrated. Our first goal is to successfully image the modulated beam with desired magnification then we will investigate various magnification and magnets combinations and optimize aberration correction.

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TUPMK014

Dipole Fringe Field Analysis of the NSLS-II Storage Ring

dipole, storage-ring, optics, lattice

1519

J. Choi, Y. Hidaka, T.V. Shaftan, C.J. Spataro, G.M. Wang
BNL, Upton, Long Island, New York, USA

Funding: DOE Contract No. DE-SC0012704
In the NSLS-II storage ring, the effect of the dipole fringe field is not negligible and was considered already at the design phase. Especially in the vertical direction, the standard simulation codes are using the parameter called FINT (fringe Field INTegral) and, if there is no specific information, it is usually set to 0.5 which is considered as the reasonable average. With the hall-probe measurement data of the NSLS-II storage ring dipoles, we evaluated measured FINTs and applied them to the beam simulation. The paper shows the resulting FINTs and their effects.

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TUPMK015

Initial Studies into Longitudinal Ionization Cooling for the Muon g-2 Experiment

emittance, experiment, storage-ring, target

1522

J. Bradley
Edinburgh University, Edinburgh, United Kingdom
J.D. Crnkovic
BNL, Upton, Long Island, New York, USA
D. Stratakis, M.J. Syphers
Fermilab, Batavia, Illinois, USA
M.J. Syphers
Northern Illinois University, DeKalb, Illinois, USA

Fermilab's Muon g-2 experiment aims to measure the anomalous magnetic moment of the muon to an unprecedented precision of 140 ppb. It relies on large numbers of muons surviving many turns in the storage ring without colliding with the sides, at least long enough for the muons to decay. Longitudinal ionization cooling is introduced with respect to Fermilab's Muon g-2 experiment in an attempt to increase storage and through this the statistics and quality of results. The ionization cooling is introduced to the beam through a material wedge, an initial simulation study is made into the positioning, material, and geometrical parameters of this wedge using G4Beamline. Results suggest a significant increase of 20 - 30% in the number of stored muons when the optimal wedge is included in the simulation.

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TUPML004

Correction of Emittance Growth Due to Quad Components in Solenoids With Quad Correctors at AWA

emittance, solenoid, linac, electron

1536

L.M. Zheng, C.-X. Tang
TUB, Beijing, People's Republic of China
M.E. Conde, D.S. Doran, W. Gai, W. Liu, J.G. Power, J.H. Shao, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA

An asymmetrical electron beam is observed on the drive beamline at Argonne Wakefield Accelerator (AWA) due to the quad components in the solenoids. An ASTRA simulation shows that the emittance will increase when the electron beam passes through solenoids with quad errors. We use two quad correctors to correct this emittance growth. A preliminary emittance correction result is presented in this paper.

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TUPML007

Short Pulse High Power RF Generation with an X-Band Dielectric Power Extractor

experiment, acceleration, linear-collider, collider

1546

J.H. Shao, M.E. Conde, D.S. Doran, W. Gai, W. Liu, N.R. Neveu, J.F. Power, C. Whiteford, E.E. Wisniewski, L.M. Zheng
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA

Short pulse high power rf generation is one of the key technologies for the Argonne Flexible Linear Collider (AFLC), a proposed 3 TeV electron-positron linear collider based on two-beam acceleration (TBA) scheme. Compared with metallic power extractors, dielectric structures have the potential to achieve lower fabrication cost and to withstand higher gradient. Recently, an X-band dielectric power extractor (a.k.a, DPETS) has been developed at the Argonne Wakefield Accelerator (AWA) facility and achieved 10⁵ MW output power when driven by a high charge 8-bunch train separated by 770 ps. The design, the cold test measurement, the preliminary high power test results, and the structure inspection will be presented in this paper.

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TUPML009

Design and Test Plan for a Prototype Corrugated Waveguide

GUI, wakefield, experiment, electron

1550

G.J. Waldschmidt, D.S. Doran, G. Ha, R. Kustom, A. Nassiri, J.G. Power, A. Zholents
ANL, Argonne, Illinois, USA
A.E. Siy
UW-Madison/PD, Madison, Wisconsin, USA

A cylindrical, corrugated wakefield accelerating structure with a 1 mm radius bore is being designed to facilitate sub-terahertz Čerenkov radiation produced by an elec-tron bunch propagating along the waveguide. A 220 GHz axial mode for the wakefield is being considered. The waveguide is being optimized to maximize the trailing wakefield potential while maintaining a ratio of the trail-ing potential to the peak decelerating voltage in the bunch, or transformer ratio, of approximately 5 for the door step peak current distribution [1]. In order to evalu-ate the manufacturing tolerances and perform rf and electron beam testing of the waveguide, a 21 GHz proto-type waveguide structure will be built consisting of re-configurable parts allowing modelling of various fabrica-tion errors. Measurements with an electron beam will be performed at the Argonne Wakefield Accelerator (AWA) test facility. Analysis of the experimental layout has been performed.

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TUPML015

Influence of Ionization and Beam Quality on Interaction of Tw-Peak Co2 Laser With Hydrogen Plasma

laser, plasma, electron, experiment

1560

P. Kumar, V. Samulyak
SBU, Stony Brook, USA
V. Samulyak, K. Yu
BNL, Upton, Long Island, New York, USA

3D numerical simulations of the interaction of a powerful CO2 laser with hydrogen jets demonstrating the role of ionization and laser beam quality are presented. Simulations are performed in support of the plasma wakefield accelerator experiments being conducted at the BNL Accelerator Test Facility (ATF). The CO2 laser at BNL ATF has several potential advantages for laser wakefield acceleration compared to widely used solid-state lasers. SPACE, a parallel relativistic Particle-in-Cell code, developed at SBU and BNL, has been used in these studies. A novelty of the code is its set of efficient atomic physics algorithms that compute ionization and recombination rates on the grid and transfer them to particles. The primary goal of the initial BNL experiments was to characterize the plasma density by measuring the sidebands in the spectrum of the probe laser. Simulations, that resolve hydrogen ionization and laser spectra, help explain several trends that were observed in the experiments.

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TUPML017

Longitudinal Phase Space Reconstruction at FLASHForward Using a Novel Transverse Deflection Cavity, PolariX-TDS

plasma, experiment, dipole, lattice

1567

R.T.P. D'Arcy, A. Aschikhin, P. González Caminal, V. Libov, J. Osterhoff
DESY, Hamburg, Germany

The FLASHForward project at DESY is an innovative beam-driven plasma-wakefield acceleration (PWFA) experiment, aiming to accelerate electron beams to GeV energies over a few centimeters of ionized gas. These accelerated beams are assessed for their capability to drive a free-electron laser. The ultra short, low emittance, and low energy spread properties of bunches produced from certain PWFA injection schemes naturally lend themselves to this task. However, these bunch lengths, typically in the few femtosecond range, are difficult to temporally resolve with traditional diagnostic methods. In order to longitudinally diagnose these bunches it is necessary to utilise the properties of a transverse RF deflecting cavity operating in a high-frequency regime. It is proposed that this type of X-band transverse deflection system, styled the PolariX-TDS due to its novel variable polarisation feature, will be introduced to the FLASHForward beam line in order to perform these single-shot longitudinal phase space measurements. This paper will concern itself with the efficacy of longitudinally reconstructing PWFA-bunches expected at FLASHForward with this TDS, with a focus on the variable bunch properties expected from early commissioning of the experiment.

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TUPML028

Photocathodes R&D for High Brightness and Highly Polarized Electron Beams at Cornell University

electron, cathode, emittance, gun

1601

L. Cultrera, J. Bae, A.C. Bartnik, I.V. Bazarov, R. Doane, A. Galdi, C.M. Gulliford, W. H. Li, J.M. Maxson, S.A. McBride, T.P. Moore, C. M. Pierce, C. Xu
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University is a leader in the development of photocathode materials for the production of high brightness electron beam sources for applications in large scale accelerators and small scale electron scattering experiments. During the last year we have also included Mott polarimetry to investigate long lifetime spin-polarized photocathodes materials. Another thrust of our laboratory is the exploration of ultra low emittance photocathodes at cryogenic temperatures, for which we are building a novel LHe cryogenic electron source. We will review updates from our lab across each of these areas.

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TUPML029

Novel Photocathode Geometry Optimization: Field Enhancing Photoemission Tips

cathode, emittance, electron, solenoid

1605

W. H. Li, I.V. Bazarov, C.M. Gulliford, J.M. Maxson
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
For photoemission sources, the extraction electric field defines the maximum achievable emission current, and hence the maximum achievable beam brightness. Recently, interest has been growing in studying photocathodes with non-flat geometries to produce local field enhancements in excess of what can be achieved with large area flat cathodes. However, such geometries cause image charge effects which require self-consistent field solvers to correctly simulate. We present a novel simulation framework which combines a full particle in cell field solver (WARP) with a fast adaptive mesh space charge particle tracker (GPT) and a parallel multi-objective genetic optimizer to explore photocathode geometries for ultra high brightnesses. A first application of this technique is also shown, namely the use of field enhanced photoemission tips to create bright beams for ultra-fast electron diffraction.

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TUPML039

First Order Sensitivity Analysis of Electron Acceleration in Dual Grating Type Dielectric Laser Accelerator Structures

laser, electron, experiment, emittance

1626

F. Mayet, R.W. Aßmann, U. Dorda, W. Kuropka
DESY, Hamburg, Germany
W. Kuropka, F. Mayet
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: Gordon and Betty Moore Foundation. Grant GBMF4744
Symmetrically driven dual-grating type DLA (Dielectric Laser Accelerator) linac structures allow for in-channel electric field gradients on the order of GV/m at optical wavelengths. In this work we study the sensitivity of important final beam parameters like mean energy, energy spread and transverse emittance on DLA drive laser as well as input beam parameters. To this end a fast specialized particle tracking code (DLATracker) is used to compute the so called first order sensitivity indices based on a large number of Monte Carlo simulation runs of an exemplary external injection based DLA experiment. The results of this work point out important stability constraints on the drive laser setup and the externally injected electron beam.

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TUPML042

Accurate Modeling of the Hose Instability in Plasma Based Accelerators

plasma, electron, damping, wakefield

1638

T.J. Mehrling, C. Benedetti, E. Esarey, W. Leemans, C.B. Schroeder
LBNL, Berkeley, USA

Funding: US Department of Energy Contract No. DE-AC02-05CH11231
The hose instability is a long standing challenge for plasma-based accelerators. It is seeded by initial transverse asymmetries of the beam or plasma phase space distributions. The beam centroid displacement is thereby amplified during the propagation in the plasma, which can lead to an unstable acceleration process. A witness beam can itself cause hosing and/or may be affected by the hosing of the drive beam. The accurate study of hosing including a witness beam is of utmost importance to facilitate stable plasma-based accelerators. In this contribution, we discuss novel methods for the mitigation of hosing and present a new model for the evolution of the plasma centroid, which enables the accurate investigation of the hose instability of drive and witness beam pair in the nonlinear blowout regime. This work enables more precise and comprehensive studies of hosing and hence, for the potential stabilization of future compact plasma-based accelerators.

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TUPML051

Studies of Collision and Compression of Pulsed Plasmas Generated by Coaxial Accelerators

plasma, electron, experiment, ion-source

1653

T. Manegold, C. Benzing, M. Iberler, J. Jacoby, P. Mahmoodi Tavana, A. Müller-Münster, B. Podßus
IAP, Frankfurt am Main, Germany

This contribution is about our recent studies of collision and compression of plasma sheaths, generated by coaxial plasma accelerators. One application is the development of a pulsed ion source producing high ion currents, coming along with high electron densities. The experiment is built up of an energy storage with up to 1,35kJ with a 2% Hydrogen in Helium gas mixture as working gas. The small fraction of Hydrogen is necessary to use the linear Stark-broadening of the H-line to determine the electron density, which is in the range up to 10¹⁵cm^-3. By the collision of two plasma sheaths in an angle of 180°, the electron density has been increased by a factor of 2.5 compared to the single plasma sheath. As an alternative, the compression of the plasma by funnel geometries has been studied. As has been found, the achieved electron densities are more than a magnitude higher, compared to the values of the plasma collision. Thus, the H-line is broadened too high to be used. Alternatively, the broadening of a copper line by the quadratic Stark-effect has been calibrated and used to determine those high electron densities of about 10¹⁸cm^-3.

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TUPML052

Characterisation of the Second Stable Orbit Generated by Transverse Resonance Island Buckets (TRIBs)

optics, resonance, experiment, emittance

1656

F. Kramer, P. Goslawski, A. Jankowiak, M. Ries, M. Ruprecht, A. Schälicke
HZB, Berlin, Germany

Funding: Federal Ministry of Education and Research
Operating the storage ring near a transverse tune resonance can generate TRIBs in the corresponding phase space, providing a second orbit twisting around the standard orbit. TRIBs as a bunch separation scheme in combination with the proposed variable bunch length storage ring BESSY VSR* represent a promising alternative to dedicated single or few bunch operation modes. The injection efficiency and stability of the two orbits at BESSY II and MLS are almost on par with and the lifetime at about 70 % of the standard user mode. Results from simulations and measurements of our present island optics will be presented. Beam parameters like the betatron motion, dispersion and emittance of both the core and island orbit will be discussed as well as the separation between the island and the core orbit. At BESSY II a dedicated test week together with the friendly users took place in the first week of February, 2018.
* A. Jankowiak et al., eds., BESSY VSR Technical Design Study, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, June 2015. DOI: 10.5442/R0001

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TUPML059

Slice Energy Spread Optimization for a 5 GeV Laser-Plasma Accelerator

plasma, laser, beam-loading, electron

1670

X. Li, P.A.P. Nghiem
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
A. Mosnier
CEA/IRFU, Gif-sur-Yvette, France

GeV-scale laser-plasma accelerating modules can be integrated into a multi-staged plasma linac for driving compact X-ray light sources or future colliders. Such a plasma module, operating in the quasi-linear regime, has been designed for the 5 GeV laser plasma acceleration stage (LPAS) of the EuPRAXIA project. Although it can be employed to optimize the total energy spread, the beam loading effect introduces an non-negligible slice energy spread to the beam. In this paper, we study the slice energy spread from linear theory, establishing a relationship between it and the laser-plasma parameters. To reduce the slice energy spread, simulations have been carried out for various plasma densities and laser strengths. The results will be discussed and compared with the theory.

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TUPML062

A Wedge Test in MICE

emittance, experiment, beam-cooling, collider

1680

T.A. Mohayai
IIT, Chicago, Illinois, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illlinois, USA
D.J. Summers
UMiss, University, Mississippi, USA

Emittance exchange mediated by wedge absorbers is required for longitudinal ionization cooling and for final transverse emittance minimization for a muon collider. A wedge absorber within the MICE cooling channel could serve as a demonstration of the type of emittance exchange needed for 6-D cooling, including the configurations needed for muon colliders. Parameters for this test have been explored in simulation and applied to experimental configurations using a wedge absorber in the MICE beam. A wedge absorber has been constructed and placed in MICE and data has been collected for both direct emittance exchange, where the longitudinal emittance decreases, and reverse emittance exchange, where the transverse emittance decreases. The simulation studies that led to the magnet configurations and beam configurations are presented.

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TUPML063

A Non-parameteric Density Estimation Approach to Measuring Beam Cooling in MICE

emittance, beam-cooling, experiment, solenoid

1684

T.A. Mohayai
IIT, Chicago, Illinois, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illlinois, USA

The goal of the international Muon Ionization Cooling Experiment (MICE) is to demonstrate muon beam ionization cooling for the first time. It constitutes a key part of the R&D towards a future neutrino factory or muon collider. The intended MICE precision requires development of analysis tools that can account for any effects (e.g., nonlinearities) which may lead to inaccurate cooling measurements. Non-parametric density estimation techniques, in particular, kernel density estimation (KDE), allow very precise calculations of the muon beam phase-space density and its increase as a result of cooling. In this study, these density estimation techniques and their application to measuring the reduction in muon beam phase-space volume and amplitude in MICE are investigated.

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TUPML065

Phase Space Density Evolution in MICE

emittance, factory, experiment, collider

1692

D. Rajaram
Illinois Institute of Technology, Chicago, Illinois, USA
V. Blackmore
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

Funding: STFC, DOE, NSF, INFN, and CHIPP
The Muon Ionization Cooling Experiment (MICE) collaboration will demonstrate the feasibility of ionization cooling, the technique proposed to cool the muon beam at a future neutrino factory or muon collider. The muon beam parameters are measured before and after the cooling cell using high precision scintillating-fibre trackers in a solenoidal magnetic field. Position and momentum reconstruction of each muon in MICE allows the development of several alternative figures of merit in addition to emittance. Contraction of the phase-space volume of the sample, or equivalently the increase in phases-pace density at its core, is an unequivocal cooling signature. Single-particle amplitude, defined as a weighted distance to the sample centroid, can be used to probe the change in density in the core of the beam. Alternatively, non-parametric statistics provide reliable methods to estimate the entire phase-space density distribution and reconstruct probability contours. The aforementioned techniques, robust to transmission losses and sample non linearities, are ideal candidates for a cooling measurement in MICE. Preliminary results are presented here*.
*Submitted by the MICE Speakers bureau, to be prepared and presented by a MICE member to be selected in due course

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TUPML066

Progress on Beam-Plasma Effect Simulations in Muon Ionization Cooling Lattices

plasma, emittance, scattering, cavity

1696

P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA
J.S. Ellison
IIT, Chicago, Illinois, USA

Funding: Work supported by the Department of Energy.
New computational tools are essential for accurate modeling and simulation of the next generation of muon-based accelerators. One of the crucial physics processes specific to muon accelerators that has not yet been simulated in detail is beam-induced plasma effect in liquid, solid, and gaseous absorbers. We report here on the development of required simulation tools and their applications to studying the properties of plasma and its effects on the beam in muon ionization cooling channels.

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TUPML074

Resonant Excitation of Accelerating Field in Dielectric Corrugated Waveguide

wakefield, experiment, electron, GUI

1715

A. Lyapin, S.T. Boogert, K. Lekomtsev
JAI, Egham, Surrey, United Kingdom
A. Aryshev
KEK, Ibaraki, Japan
A.A. Tishchenko
MEPhI, Moscow, Russia

Funding: This project has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 655179.
Beam driven dielectric wakefield accelerators (DWAs) [*] typically operate in the terahertz frequency range, which pushes the plasma breakdown threshold for surface electric fields into the multi GV/m range. DWA technique allows one to accommodate a significant amount of charge per bunch, and opens access to conventional fabrication techniques for the accelerating structures. Resonant excitation of coherent Cherenkov radiation in DWA by a multi-bunch beam was used for selective resonant mode excitation [**] and enhancement of accelerating wakefield [***]. We investigate the resonant excitation of Cherenkov Smith-Purcell radiation [****] in a corrugated cylindrical waveguide by a multi-bunch electron beam. The accelerating field is calculated using Particle in Cell simulations and some basic post-processing is done in order to estimate the possible enhancement of the accelerating field. The aim of this work is to investigate regimes of the resonant excitation that can potentially produce accelerating gradients above 1 GV/m.
* C. Jing, Rev. Acc. Phys. and Tech. 9, 127 (2016).
** G. Andonian, APL 98, 202901 (2011).
*** J.G. Power, PRSTAB 3, 101302 (2000).
**** A.A. Ponomarenko, A.A. Tishchenko, NIMB 309, 223 (2013).

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TUPML077

Development of Physical Processes in Geant4 for Simulation of ISOL Target-Ion-Source System

target, proton, ISOL, ion-source

1724

P. Lee, Y.-S. Cho, J.J. Dang, H.S. Kim, H.-J. Kwon, S. Lee, Y.G. Song, S.P. Yun
Korea Atomic Energy Research Institute (KAERI), Gyeongbuk, Republic of Korea

Funding: This work has been supported through KOMAC operation fund of KAERI and the NRF of Korea grant funded by the Korea government (MSIT) (No. NRF-2017M2A2A6A02071070).
Geant4 physical processes for simulating diffusion and effusion of radioactive ions in matter have been developed for optimizing ISOL target-ion-source (TIS) system. The developed processes simulate motions of radioactive ions with sub-eV kinetic energy in the TIS geometry. The processes consist of diffusion, effusion, and radioactive decay modules, and they are designed to work seamlessly with other implemented physics lists, extending capability of the Geant4 toolkit to more complicated applications in the field of nuclear physics. The diffusion probability is analytically calculated by using the well-known Fick's formula. The effusive flow of neutral atoms is interpreted in terms of kinetic molecular theory of gases, where the interaction between atoms and the wall of a target container is described by employing Lorentz-Lambert model. By the help of newly implemented processes, it is able to simulate the release of radioactive ions from the irradiation of a proton beam on the TIS system with different geometrical parameters in a single environment. Here, we present the status of the development and plans for further improvements.

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WEXGBE3

IBS Studies at BESSY II and MLS

emittance, scattering, radiation, damping

1755

T. Mertens
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
T. Atkinson, J. Feikes, P. Goslawski, J.G. Hwang, A. Jankowiak, J. Li, D. Malyutin, Y. Petenev, M. Ries, I. Seiler
HZB, Berlin, Germany

Intrabeam Scattering (IBS) effects will become a limiting factor for the attainable emittances and single-bunch currents in future electron storage rings and light sources. IBS studies were performed for BESSY II at the Helmholtz-Zentrum Berlin (HZB) and for the Metrology Light Source (MLS) at the Physikalisch-Technische Bundesanstalt (PTB) to quantify the IBS contributions to equilibrium beam sizes in these machines and make predictions for the BESSY II upgrade project, BESSY VSR. The energy dependence of IBS effects (γ −4 ) makes especially the MLS machine susceptible to IBS effects due to the relatively low energy ranges at which it can be operated (50 MeV-630 MeV). We compare experimental data with simulations and present IBS simulation results for BESSY VSR.

Slides WEXGBE3 [0.916 MB]

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WEPAF003

Beamline Architect

interface, quadrupole, software, solenoid

1812

J.D. Kunz, C.M. Conrad, L.M. Romero
Anderson University, Anderson, USA

Funding: Indiana Space Grant Fellowship Program 2015-2018, subaward number 4103-82252
Beamline Architect is a new particle accelerator simulation tool. Currently, two of the most widely used tools in this field are G4beamline and COSY Infinity. While these codes are fast and quite accurate, sometimes their interfaces can be time-consuming for students to learn, particularly undergraduate students or students whose primary field is not accelerator physics. Without Beamline Architect, each code has its own high-level language that must be manually written into a file and then executed on the command line. Moreover, sometimes the use of both simulation tools is warranted in order to check for consistency between the codes. Writing the codes by hand or translating between software can sometimes be cumbersome, even for experts. Furthermore, knowledge of an additional language, such as Python, is required in order to analyze the outputs of the codes (which may be in different formats from one another). Beamline Architect is a tool that provides a graphical user interface to G4beamline and COSY Infinity. This lets the user build a particle accelerator channel in 3D with or without using code. The channel may then be saved, exported, translated, or run. Any output data will be plotted in Beamline Architect using Python, since it is both flexible aesthetically and quite standard in the particle accelerator community. For undergraduate and non-accelerator students, Beamline Architect allows a hands-on experience with accelerator simulations. Some applications for these students include health physics radiation dosimetry problems, medical imaging mechanics, security scanner simulations, and (of course) accelerator channel design for particle physics experiments. For experts, Beamline Architect provides visual confirmation of the channel and a faster, more consistent way of cross-referencing results between the codes.

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WEPAF014

Commissioning the Superconducting Magnetic Inflector System for the Muon g-2 Experiment

storage-ring, experiment, injection, MMI

1844

N.S. Froemming
CENPA, Seattle, Washington, USA
K.E. Badgley, H. Nguyen, D. Stratakis
Fermilab, Batavia, Illinois, USA
J.D. Crnkovic
BNL, Upton, Long Island, New York, USA
L.E. Kelton
UKY, Kentucky, USA
M.J. Syphers
Northern Illinois University, DeKalb, Illinois, USA

The Fermilab muon g-2 experiment aims to measure the muon anomalous magnetic moment with a precision of 140 ppb - a fourfold improvement over the 540 ppb precision obtained in the BNL muon g-2 experiment. Both of these high-precision experiments require an extremely uniform magnetic field in the muon storage ring. A superconducting magnetic inflector system is used to inject beam into the storage ring as close as possible to the design orbit while minimizing disturbances to the storage-region magnetic field. The Fermilab experiment is currently in its first data-taking run, where the Fermilab inflector system is the refurbished BNL inflector system. This discussion reviews the Fermilab inflector system refurbishment and commissioning.

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WEPAF018

Proposed BPM-Based Bunch Crabbing Angle Monitor

cavity, site, electron, diagnostics

1860

P. Thieberger, M.G. Minty, C. Montag
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-AC02-98CH10886 with the US Department of Energy.
A tilted bunch traversing a button beam profile monitor will produce signals on opposite pickup electrodes that will have different degrees of distortion depending on the tilt angle. In particular, the zero-crossing time difference between the two signals will be approximately proportional to the tilt angle. We perform simulations to study this effect as a possible diagnostic tool for measuring the crabbing angles in a future electron-ion collider.

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WEPAF019

Fast Readout Algorithm for Cylindrical Beam Position Monitors Providing Good Accuracy for Particle Bunches with Large Offsets

FPGA, electron, collider, pick-up

1864

P. Thieberger, D.M. Gassner, R.L. Hulsart, R.J. Michnoff, T.A. Miller, M.G. Minty, Z. Sorrell
BNL, Upton, Long Island, New York, USA
A.C. Bartnik
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by Brookhaven Science Associates, LLC, under Contract No. DE-AC02-98CH10886 with the US Department of Energy.
A simple, analytically correct algorithm is developed for calculating 'pencil' beam coordinates using the signals from an ideal cylindrical beam position monitor (BPM) with four pickup electrodes (PUEs) of infinitesimal widths. The algorithm is then applied to simulations of realistic BPMs with finite width PUEs. Surprisingly small deviations are found. Simple empirically determined correction terms reduce the deviations even further. Finally, the algorithm is used to study the impact of beam-size upon the precision of BPMs in the non-linear region. As an example of the data acquisition speed advantage, a FPGA-based BPM readout implementation of the new algorithm has been developed and characterized

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WEPAF036

Energy Independence in Optical Transition Radiation Imaging

radiation, electron, diagnostics, optics

1898

J. Wolfenden, R.B. Fiorito, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
R.B. Fiorito, C.P. Welsch, J. Wolfenden
The University of Liverpool, Liverpool, United Kingdom

Funding: This work was supported by the EU under Grant Agreement No. 624890 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
The exploitation of optical transition radiation (OTR) in imaging-based diagnostics for charged particle beams is a well-established technique. Simulations of the expected OTR transverse beam profiles are therefore important in both the design of such imaging systems and the analysis of the data. Simulating OTR images is relatively straightforward for low energy electron beams. However, in the near future electron machines will be using high-energy and low-emittance beams. Using such parameters can be challenging to simulate, and can be limiting in their account of practical factors, e.g. chromatic aberrations. In this work we show systematically that the use of low-energy parameters in high-energy OTR image simulations induces little deviation in the resulting transverse beam profiles. Simulations therefore become much easier to perform, and further analysis may be performed. This opens up exciting opportunities to perform simulations quicker and with reduced demands on the computation requirements. It will be shown in this contribution how this approach will enable enhanced ways to optimize OTR diagnostics.

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WEPAF041

Use of Dimension-Reduction Techniques With Multi-Objective Genetic Algorithms to Improve the Vertical Emittance and Orbit at CESR

emittance, storage-ring, lattice, electron

1901

W.F. Bergan, I.V. Bazarov, C.J. Duncan, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
D. Liarte, J.P. Sethna
Cornell University, Ithaca, New York, USA

Funding: DOE DE-SC0013571 NSF DGE-1650441
In order to reduce the vertical emittance at the Cornell Electron Storage Ring (CESR), we first measure and correct the vertical orbit, dispersion, and coupling. However, due to the finite resolution of our optics measurements, we still retain a significant residual emittance. In order to correct this further, we made use of the theory of sloppy models, according to which certain high-dimensionality systems can be modeled with significantly fewer "eigenparameters" that still contain most of the effect on the desired objective, in this case, the emittance.* However, we noted that using these knobs for tuning often resulted in increased vertical orbit errors. In an attempt to constrain these, we have applied multi-objective genetic algorithms to this problem. We have found that it can be more efficient to run such algorithms using our eigenparameters as the genes to be varied, as opposed to the raw magnet values. When running with the first 8 such knobs as genes, we can get either orbits or beam sizes as good as we obtain with our regular emittance-tuning algorithm which uses all the corrector magnets.
*K.S. Brown and J.P. Sethna, Phys. Rev. E 68, 021904 (2003).

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WEPAF050

Simulations of 3D Charge Density Measurements for Commissioning of the PolariX-TDS

cavity, electron, MMI, lattice

1930

D. Marx, R.W. Aßmann, R.T.P. D'Arcy, B. Marchetti
DESY, Hamburg, Germany

The prototype of a novel X-band transverse deflection structure, the Polarizable X-band (PolariX) TDS*, is currently being prepared for installation in the FLASHForward beamline** at DESY in early 2019. This structure will have the novel feature of variable polarization of the deflecting mode, allowing bunches to be streaked at any transverse angle, rather than at just one angle as in a conventional cavity. By combining screen profiles from several streaking angles using tomographic reconstruction techniques, the full 3D charge density of a bunch can be obtained***. It is planned to perform this measurement for the first time during commissioning of the structure. In this paper, simulations of this measurement are presented and the effects of jitter are discussed.
*P Craievich et al. paper THPAL068, this conference
**A Aschikhin et al. Nucl. Instr. Meth. Phys. Res. A., vol.806, pp.175-183, 2018
***D Marx et al. J. Phys.: Conf. Ser., vol.874, p.012077, 2017

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WEPAF060

Non-Invasive Bunch Length Diagnostics for High Intensity Beams

detector, radiation, electron, real-time

1964

S.V. Kuzikov, S.P. Antipov
Euclid TechLabs, LLC, Solon, Ohio, USA
S.V. Kuzikov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Modern particle accelerators utilize photoinjectors and compression schemes to produce short high peak current electron bunches for various applications like x-ray free electron lasers, high gradient beam driven acceleration and others. Bunch length detection is a desired diagnostics for such machines. In this paper we describe a non-invasive, real-time detector which can be retrofitted into an existing beamline and measure the bunch length in real time using interferometric methods. Diffraction radiation is the mechanism to be used to produce a measurable signal without intercepting the beam. This became possible as sensitivity of pyrodetectors improved over the years, while peak beam power grew. For high peak current beams there is a possibility of a single shot measurement. This can be done with a pair of closely placed vacuum breaks that create a spatial correlation of the generated signals which can be measured by a pyro-detector array or a THz camera. The bunch length is determined from the correlation data using an iterative beam profile recovery algorithm.

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WEPAF076

Availability Studies Comparing Drive Beam and Klystron Options for the Compact Linear Collider

klystron, operation, linac, software

2013

O. Rey Orozko, S. Döbert, M. Jonker
CERN, Geneva, Switzerland

The initial proposal for the Compact Linear Collider (CLIC) is based on a two beam-scheme to accelerate the main colliding beams. For low collision energies, the main beam could also be accelerated by powering the accelerating structures with klystrons instead of the two-beam scheme. This paper studies the feasibility of this new alternative in terms of machine availability. An implemented bottom-up availability model considers the components failure modes to estimate the overall availability of the system. The model is defined within a Common Input Format scheme and the AvailSim3 software package is used for availability simulations. This paper gives an overview of the systems affecting the beam powering availability and makes recommendations for availability improvements.

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WEPAG002

Tunable Q-Factor Gas-Filled RF Cavity

cavity, coupling, hadron, plasma

2064

M.D. Balcazar, A. Moretti, A.V. Tollestrup, A.C. Watts, K. Yonehara, R.M. Zwaska
Fermilab, Batavia, Illinois, USA
M.A. Cummings, A. Dudas, R.P. Johnson, G.M. Kazakevich, M.L. Neubauer
Muons, Inc, Illinois, USA

Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795.
Fermilab is the main institution to produce the most powerful and wide-spectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gas-filled RF cavity has been proposed. The goal of this measurement is to study a tunable Q-factor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, the measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error.

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WEPAK008

Reconstructing Space-Charge Distorted IPM Profiles with Machine Learning Algorithms

electron, space-charge, GUI, network

2099

D.M. Vilsmeier, M. Sapinski, R. Singh
GSI, Darmstadt, Germany
J.W. Storey
CERN, Geneva, Switzerland

Measurements of undistorted transverse profiles via Ionization Profile Monitors (IPMs) may pose a great challenge for high brightness or high energy beams due to interaction of ionized electrons or ions with the electromagnetic field of the beam. This contribution presents application of various machine learning algorithms to the problem of reconstructing the actual beam profile from measured profiles that are distorted by beam space-charge interaction. (Generalized) linear regression, artificial neural network and support vector machine algorithms are trained with simulation data, obtained from the Virtual-IPM simulation tool, in order to learn the relation between distorted profiles and original beam dimension. The performance of different algorithms is assessed and the obtained results are very promising for testing with simulation data.

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WEPAK010

Simulations and Measurements of the BPM Non Linearity and Kicker Timing Influence on the Tune Shift With Amplitude (TSWA) Measurement at BESSY II

kicker, optics, factory, diagnostics

2107

F. Kramer, P. Goslawski, J.G. Hwang, A. Jankowiak, P. Kuske, M. Ruprecht, A. Schälicke
HZB, Berlin, Germany

The Tune Shift With Amplitude (TSWA) does not only determine the position of the stable fix points for the Transverse Resonant Island Buckets (TRIBs) but also represents a global observable for the nonlinear optics in general. For theoretical investigations of the TRIBs a reliable nonlinear optics of the machine is required and thus all measurable global observables for the nonlinear optics are of great interest. The measurement of the TSWA for the BESSY II standard optics was performed using an injection kicker to excite high amplitude betatron oscillations and then extract the amplitude dependant frequency from the synchrotron radiation damped oscillation with a Hilbert transformation. With TRIBs optics the injection kicker was not able to sufficienty excite the beam. The impact and correctability of the BPM nonlinearity at the reached amplitudes and the reason for the failure of the excitation method for our TRIBs optics shall be looked onto in this paper.

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WEPAL003

Baseband Simulation Model of the Vector RF Voltage Control System for the J-PARC RCS

controls, feedback, cavity, software

2144

F. Tamura, M. Nomura, T. Shimada, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
KEK, Tokai, Ibaraki, Japan

Vector rf voltage feedback control for the wideband magnetic alloy cavity of the J-PARC RCS is considered to be employed to compensate the heavy beam loading caused by high intensity proton beams. A prototype system of multiharmonic rf vector voltage control has been developed and is under testing. To characterize the system performance, full rf simulations could be performed by software like Simulink, while the software is proprietary and expensive. Also, it requires much computing power and time. We performed the simplified baseband simulations of the system in z-domain by using free software, Scilab and Python control library. It seems to be beneficial for searching the parameters that the baseband simulation can be performed quickly. In this presentation, we present the setup and results of the simulations. The simulations well reproduce the open and closed loop responses of the prototype system.

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WEPAL013

Design of the Diagnostic Stations for the ELI-NP Compton Gamma Source

radiation, electron, optics, linac

2173

M. Marongiu
INFN-Roma, Roma, Italy
M. Castellano, E. Chiadroni, G. Di Pirro, G. Franzini, A. Giribono, V. Shpakov, A. Stella, A. Variola
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy

A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches, 16 ns spaced, with a nominal charge of 250 pC will collide with the laser beam in the interaction point. Electron beam spot size is measured with optical transition radiation (OTR) profile monitors. Furthermore, OTR angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor beam envelope, one may perform a distributed energy measurement along the machine. This will be useful, for instance, during the commissioning phase of the GBS in order to verify the correct functionality of the C-Band accelerating structures, due to the fact that there are OTR screens after each accelerating module. This paper deals with the studies of different optic configurations to achieve the field of view, resolution and accuracy in order to measure the energy of the beam. Several configurations of the optical detection line will be studied with simulation tools (e.g. Zemax).

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WEPAL017

Adaptive Feedforward Control Design Based on Simulink for the J-PARC LINAC LLRF System

controls, LLRF, cavity, linac

2187

S. Li
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
Z. Fang, Y. Fukui, K. Futatsukawa, F. Qiu
KEK, Ibaraki, Japan
S. Mizobata, Y. Sato, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan

In j-parc linac, for dealing with high beam loading effect, an adaptive feedforward control method which based on iterative learning control was put forward. At the same time, in order to verify its effectiveness before it is officially put into use, an llrf system simulation model was built in simulink, matlab. In this paper, the architecture of llrf system simulation model will be introduced. The result of iterative learning control (ILC) is summarized.

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WEPAL028

Study of the Influence of the CSR Impedance on the Synchronous Phase Shift at KARA

impedance, synchrotron, storage-ring, radiation

2223

P. Schönfeldt, E. Blomley, M. Brosi, E. Bründermann, J. Gethmann, B. Kehrer, A.-S. Müller, A.I. Papash, J.L. Steinmann
KIT, Karlsruhe, Germany

Funding: This work has been supported by the German Federal Ministry of Education and Research (Grant No. 05K16VKA) and the Helmholtz Association (Contract No. VH-NG-320).
Measurements of the bunch current dependent synchronous phase shift are a standard method to characterize the impedance of a storage ring. To study this shift, different experimental approaches can be used. In this contribution, we first derive the phase shift caused by the impedance describing the emission of coherent synchrotron radiation (CSR) based on numerical simulations of the longitudinal phase space. The predicted shift is compared to measurement results obtained by time-correlated single photon counting.

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WEPAL030

Deep Learning Based Predictive Control for RFT-30 Cyclotron

controls, cyclotron, network, operation

2230

Y.B. Kong, M.G. Hur, E.J. Lee, J.H. Park, H.S. Song, S.D. Yang
KAERI, Jeongeup-si, Republic of Korea

Successful construction of the control system is an important problem in the accelerator. The RFT-30 cyclotron is 30 MeV cyclotron for radioisotope production and fundamental researches. To operate the RFT-30 cyclotron for beam irradiation, the human operators should carefully manipulate the control parameters. If the control does not function properly, it becomes difficult to handle the cyclotron and cannot perform the accurate operations for the control. In this work, we propose a deep learning based model predictive control approach for the RFT-30 cyclotron. The proposed approach is composed of two steps: system identification and a control design. In the system identification procedure, the proposed approach constructs the predictive model of the accelerator using the deep learning approach. In the control design stage, the controller finds the optimal control inputs by solving the optimization problem. To analyze the performance of the proposed approach, we applied the approach into the RFT-30 cyclotron.

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WEPAL033

Development of Real-Time Mass Analysis System with Permanent Magnet for Ion Beam

ion-source, extraction, permanent-magnet, ECR

2236

Y. Takeuchi, Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan

In order to analyze time variation of the ion species in a pulse, we are developing a mass analysis system that has multiple collector electrodes to detect several ion species simultaneously. Strong permanent magnets can generate 1T magnetic field and the size of the analyzing magnet system can be compact. The detected signals are scanned by a fast multiplexer. The scanning rate is 2 MHz, so that all electrode signals of the 16 channels are scanned in 8 μs period. In this paper, details of the design of the analysis system, and preliminary beam extraction test results with prototype of the system are described.

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WEPAL037

Simulation Study on Luminosity Feedback for Horizontal Beam Stabilization at Superkekb

luminosity, feedback, ground-motion, monitoring

2250

C.G. Pang, P. Bambade
LAL, Orsay, France
Y. Funakoshi, S. Uehara
KEK, Ibaraki, Japan

The SuperKEKB e⁺ e^- collider uses highly focused ultra-low emittance bunches colliding every 4 ns to reach a very high luminosity of 8× 10³⁵ cm^-2s^-1. It is quite essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between the colliding beams in the presence of ground motion disturbances. For the horizontal motion, a luminosity monitoring system, based on measuring the rate of the Bhabha process at vanishing scattering angle, is developed as input signal to the feedback system. The relative precision needed for this monitor is studied in detail, for the different successive stages of luminosity operation, based on a full simulation of this system, including the detector, DAQ, lock-in amplifier, and feedback control.

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WEPAL038

First Tests of Superkekb Fast Luminosity Monitors During 2018 Phase-2 Commissioning

luminosity, monitoring, detector, feedback

2254

C.G. Pang, P. Bambade, S. Di Carlo, D. Jehanno, V. Kubytskyi, Y. Peinaud, C. Rimbault
LAL, Orsay, France
Y. Funakoshi, S. Uehara
KEK, Ibaraki, Japan

The SuperKEKB e⁺e^- collider aims to reach a very high luminosity of 8× 10³⁵ cm^-2s^-1, by using highly focused ultra-low emittance bunches colliding every 4 ns, it is essential to have an orbit feedback system at the Interaction Point (IP) to maintain the optimum overlap between two colliding beams. Luminosity monitoring systems including LumiBelle2 and ZDLM as input to dithering feedback system used to stabilize the horizontal orbit at the IP were developed and will be described, including the detectors, mechanical set-up, DAQ. Preliminary measurements and analysis of background and first stage luminosity monitoring data collected will be reported and compared with simulation.

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WEPAL049

Simulating Non-Relativistic Beams Using Helical Pulse Lines

impedance, site, ECR, GUI

2288

C.J. Richard
NSCL, East Lansing, Michigan, USA
S.M. Lidia
FRIB, East Lansing, USA

Funding: Work supported by the US Department of Energy, Office of Science, High Energy Physics under Cooperative Agreement award number DE-SC0018362.
Benchtop calibration of capacitive beam position monitors (BPMs) in low energy beamlines is challenging due to non-relativistic effects. Typical benchtop calibrations cannot account for these effects because they rely on speed of light fields transmitted along a straight wire. However, it is possible to replicate the electromagnetic fields generated by non-relativistic beams using a helical line pulse instead of a straight wire. In order to properly replicate the fields from a beam, a method must be developed for tailoring input pulses into the helical line to match bunch shape and a model of the impedance of the helix should be developed to assist with matching. This paper uses the sheath helix model to analyze signal propagation along a helical line in the time domain, with attention to dispersive effects and impedance matching. The results from this model are then compared to Microwave Studio simulations.

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WEPAL065

Development of a Gas Sheet Beam Profile Monitor for IOTA

detector, space-charge, proton, plasma

2326

S. Szustkowski, B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay
Northern Illinois Univerity, DeKalb, Illinois, USA
D.J. Crawford
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy, Office of High Energy Physics, General Accelerator Research and Development (GARD) Program
A nitrogen gas sheet will measure the two dimensional transverse profile of the 2.5 MeV proton beam in IOTA. The beam lifetime is limited by the interaction with the gas, thus a minimally invasive instrument is required. To produce a gas sheet with the desired density and thickness, various nozzle types are being investigated, including rectangular capillary tubes for gas injection and skimmers for final shaping of the gas. It is essential to meet vacuum requirements in the interaction chamber while maintaining the precise thickness and density of the gas, without significantly affecting the beam lifetime. The current design of a gas sheet beam profile monitor and present status will be discussed.

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WEPAL069

Reentrant Cavity Resonator for Low Intensities Proton Beam Measurements

pick-up, cavity, resonance, scattering

2341

S. Srinivasan, P.-A. Duperrex
PSI, Villigen PSI, Switzerland

A non-interceptive beam current monitor has been developed to investigate the measurement possibilities of low-intensity beams down to 1 nA for proton therapy machines without the drawback of interceptive monitors. This works on the principle of a reentrant cavity resonator such that its fundamental mode resonance frequency of 145.7 MHz matches the second harmonic of the pulse repetition rate of the cyclotron beam i.e. 72.85 MHz. The Driven Modal analysis from the simulation tool ANSYS HFSS was used for parametric model development and to optimize design parameters such as e.g. the position of the inductively coupled pick-ups. A ceramic plate has been inserted in the resonator gap to relax the precision required during manufacturing. A test bench has been designed and constructed for the characterization tests of the prototype. Comparison of the simulated and the experimental scattering parameter from the test bench shows a good agreement.

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WEPAL072

A Novel Longitudinal Laserwire to Non-Invasively Measure 6-Dimensional Bunch Parameters at High Current Hydrogen Ion Accelerators

laser, emittance, detector, linac

2349

S.M. Gibson, A. Bosco
Royal Holloway, University of London, Surrey, United Kingdom
S.E. Alden, A. Bosco, S.M. Gibson
JAI, Egham, Surrey, United Kingdom
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom
J.K. Pozimski
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom

Funding: We acknowledge funding by the STFC Grant ST/P003028/1 and the John Adams Institute at Royal Holloway, University of London.
Optical methods for non-invasive beam diagnostics of high current H⁻ ion accelerators have been developed in recent years*, **. Such laserwires typically measure a 1D beam profile and/or 2D transverse emittance from the products of photo-detached ions as a laser beam is scanned across the H⁻ beam. For laser pulse durations (~80ns) longer than the RF period (~3ns), the detector integrates many complete bunches, enabling only transverse beam monitoring. This paper presents a new technique to capture a series of time resolved transverse emittance measurements along the bunch train. A fast (~10ps) pulsed laser photo-detaches ions within each bunch and is synchronized to sample consecutive bunches at certain longitudinal positions along each bunch. A fast detector records the spatial distribution and time-of-flight of the neutralized H⁰, thus both the transverse and longitudinal emittance are reconstructed. We present simulations of a time varying pulsed laser field interacting within an H⁻ bunch, and estimate the yield, spatial and time distributions of H⁰ arriving at the detector. We summarise the design of a recently funded longitudinal laserwire being installed in FETS at RAL, UK.
* NIM-A, 830, p526-531, T. Hofmann et al
** T. Hofmann et al, 'Commissioning of the Operational Laser Emittance Monitors for LINAC4 at CERN' IPAC18.

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WEPMF005

Design and Testing of a 12 kW, 352 MHz Solid State rf System at the Advanced Photon Source

cavity, controls, operation, GUI

2378

D. Horan, D.J. Bromberek, A. Goel, T.J. Madden, A. Nassiri, G.J. Waldschmidt
ANL, Argonne, Illinois, USA

A 12 kW, 352 MHz rf power amplifier system was designed and constructed at the Advanced Photon Source as a research and development test bed for eventual development of a 200 kW cw rf system capable of supporting accelerator beam operation. The system utilizes six 2 kW laterally diffused metal oxide field effect transistor (MOSFET) rf amplifiers, an output cavity combiner terminated with a WR2300 waveguide output flange, and a monitoring system based on programmable logic controller technology. The combining cavity has a total capacity of 10⁸ two-kilowatt inputs to support eventual operation up to 216kW maximum output power. Design details and operational performance of the 12 kW system will be discussed.

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WEPMF019

Conceptual Design of the eRHIC Storage Ring Magnets

storage-ring, dipole, sextupole, quadrupole

2407

H. Witte, J.S. Berg, S. Tepikian
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Presently the electron-ion collider eRHIC is under design, which aims to provide a facility with a peak luminosity of 10³⁴cm^-2sec^-1. Part of the eRHIC accelerator is the addition of an electron storage ring to the existing tunnel. This paper describes the magnets required for this storage ring. The necessary bending is provided by a triplet of dipole magnets, which generate excess bending to create additional radiation damping to allow a larger beam-beam tune shift. Each triplet consists of two long, low field magnets and a short, high-field magnet. This paper also describes the quadrupole and sextupole magnets necessary for this machine. All magnets require a large aperture to accommodate the beam-pipe.

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WEPMF022

Coulped Multiphysics Simulation for the Water Cooling Layout of a Rhodotron Cavity

cavity, operation, vacuum, electron

2416

L. Yang, X. He, H. Li, S.Q. Liao
CAEP/IFP, Mainyang, Sichuan, People's Republic of China

A Rhodotron-based electron accelerator served as micro-focused X-ray source is under development at IFP, CAEP. The RF-cavity, running in long pulse/ CW mode, will deliver 9 MeV energy to electron beams after multiple accelerations within the same field at a frequency of 10⁷.5MHz. A substantial amount of average power loss with tens of kW will be dissipated on the RF surface of the cavity to maintain the operational field level. Efficient water cooling is critical to prevent large scale temperature rise for stable operation sake. Reasonable prediction of temperature rise becomes essential to assess a certain cooling layout in the design phase. The frequency drift and thermal stress on account of temperature variation and gradient on cavity wall respectively, could be computed accordingly. This paper presents a comprehensive coupled simulation involving electromagnetic, thermal and structural for the RF-cavity of Rhodotron.

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WEPMF030

Optimization of Klystron Efficiency with MOGA

klystron, cavity, electron, bunching

2419

C. Meng, X. He, S. Pei, S.C. Wang, O. Xiao, Z.S. Zhou
IHEP, Beijing, People's Republic of China

As the very important element of accelerator the klystron provide power to cavities for accelerating. Considering the accelerator cost of construction and running, the improvement of klystron efficiency is one developing hotspot of klystron research. In this paper the optimization method of klystron efficiency with MOGA based on 1D simulation program is proposed and the influences on klystron efficiency will be discussed.

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WEPMF031

Development of a High-Power High-Directivity Directional Coupler and Four Power Dividers for S-Band

coupling, GUI, vacuum, MMI

2422

X. He, J. Lei, J.R. Zhang
IHEP, Beijing, People's Republic of China

A novel Bethe-hole S band directional coupler has been designed based on some structural optimizations, the prototype has been tested with a Directivity of more than 30 dB. The new directional coupler can also hold higher power compared to the old type, which is more useful for the future accelerator applications. Four power dividers using different structures are studied and the best one is chosen for fabrication. The prototype with matching rod in the middle has got qualified microwave cold test results and has been used during the whole microwave commissioning of an accelerating structure, the performance is quite stable.

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WEPMF033

RF Study And Cold Test of an S-band Spherical Cavity Pulse Compressor

cavity, coupling, vacuum, klystron

2429

J. Lei, X. He, M. Hou, X.P. Li, G. Pei, H. Wang, J.B. Zhao
IHEP, Beijing, People's Republic of China
S. Shu
Institute of High Energy Physics (IHEP), Chinese Academy of Sciences, Beijing, People's Republic of China

An S-band (2856 MHz) spherical cavity pulse compressor has been designed, fabricated and tested in the Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS). The pulse compressor consists of a special 3 dB coupler and only one spherical energy storage cavity, two TE114 modes are chosen to oscillate in which for fairly high unload Q factor. The prototype was made of aluminum for studying the performance of the pulse compressor and checking the validity of the simulations. The cold test results of the aluminum cavity are also presented. The copper coating on the whole internal surface of the aluminum spherical cavity is in progress and the test results will also be presented in the future.

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WEPMF044

Updates on the DC Field Dependence Cavity

cavity, niobium, multipactoring, SRF

2465

J.T. Maniscalco, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Work at Cornell has demonstrated good agreement between a theoretical model by A. Gurevich of the anti-Q-slope (a field-dependent decrease of the microwave surface resistance) and experimental results from impurity-doped niobium. As a corollary, the model predicts that a strong DC magnetic field applied parallel to the RF surface will produce a similar decrease in surface resistance. In order to explore this prediction for many materials, we have designed a new coaxial cavity with a strong, uniform DC field superimposed over a weak RF field on a removable and replaceable niobium sample. Here we present updates on the progress of this new cavity.

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WEPMF051

Multipacting in an RF Window: Simulations and Measurements

multipactoring, electron, resonance, gun

2483

M. Bousonville, S. Choroba
DESY, Hamburg, Germany

Electron guns are used in the accelerators of the European XFEL and FLASH. They are operated at 1.3 GHz. The RF peak power is 5 MW at 650 us pulse width and 10 Hz repetition rate. In order to understand the multipacting that occurs during conditioning, it was simulated in the RF window type that is used for the electron gun in the XFEL. The reduction in secondary emission yield associated with conditioning was taken into account. Since the RF windows are tested with high power on a test stand before their use, without the electron gun, measurement results are available which are compared with the simulation results. The main advantage of the simulation compared to the measurement is that the locations of multipacting can be determined in the RF window. This could be helpful for the development of high-power RF components in the future, in order to detect pronounced multipacting resonances even before production and to avoid them by design changes.

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WEPMF058

Anomaly Detection for Cavity Signals - Results from the European XFEL

cavity, flattop, FEL, beam-loading

2502

A.S. Nawaz, S. Pfeiffer
DESY, Hamburg, Germany
G. Lichtenberg
HAW, Hamburg, Germany
P. Rostalski
Institute for Electrical Engineering in Medicine, Lübeck, Germany

The data throughput of the European XFEL DAQ is about 1.5 Gb/s. Data depicting the cavity signal behavior is currently only saved manually. This either happens, when cavity tests are being performed, or an operator detects a fault in the cavity system, that has to be further investigated. Those instances of interest are neither systematically nor automatically stored. It can therefore be assumed that unwanted or degraded cavity behavior is detected late or not at all. It is proposed to change the focus from detecting known faults (such as quenches) to additionally detect anomalies in the cavity system behavior. In order to detect anomalies in the cavity signals, an algorithm is proposed using a cavity model. It aims on finding those data sets, which diverge from the nominal cavity behavior, saving those instances for later analysis. The nominal behavior is defined by the cavity electromagnetic resonance model with beam loading as well as the model for the mechanical oscillations due to the Lorentz Forces. By using such an approach, the detection of anomalies, as well as faults could be automated. This contribution aims to summarize the influence of beam loading on the detection and gives examples for anomalies that were found in several cavities.

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WEPMF062

Simulation of Cavity Conditioning for the Diamond SCRF Cavity

cavity, GUI, coupling, operation

2509

S.A. Pande, C. Christou, P. Gu
DLS, Oxfordshire, United Kingdom

Diamond SCRF cavities are pulse conditioned every week in order to keep them operating reliably. During conditioning, the cavities are detuned in order to sweep the standing wave through the waveguide. To match these cavities at lower voltage (typically < 1.4 MV) and at higher power, 3 stub tuners are used in the waveguide feed. Simulations with CST studio show that a strong SW field exists between the RF window and the matching posts. As the cavity is detuned the electric field maximum passes through the window causing heating of the ceramic. Temperature measurements with thermal camera reveal that the temperature of the window increases to maximum when the cavity is detuned towards higher frequency. Based on the simulation results and the measurements, it was decided to reduce the conditioning voltage. These results are summarised.

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WEPMF075

Performance Measurements and Analysis of Jitter Like Events for the PS Injection Kicker System

kicker, controls, operation, injection

2549

A. Ferrero Colomo, J.C.C.M. Borburgh, L. Ducimetière, L.M.C. Feliciano, V. Forte, M.A. Fraser, T. Kramer, L. Sermeus
CERN, Geneva, Switzerland

In the framework of the LIU project, several modifications have been made to the CERN PS injection kicker system during the winter stop 2016-2017 (EYETS). Current waveform and beam-based measurements were carried out in 2017 to validate the implemented design changes by observing the magnetic field impact on the beam. During these long-term measurements, increased values for the rise and fall times were observed when compared to single shot observations of the current waveform. An unknown source of jitter-like pre-firing in the main switch has been identified, creating an additional challenge to meet the already tight system rise and fall time specifications. This paper briefly describes the efforts made to fine tune the pulse generator after the EYETS, summarises the optimised configuration and analyses the observed jitter events. A new triggering system design is briefly outlined to address the issue.

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WEPMF082

Design and Construction of the CERN PS Booster Charge Exchange Injection Chicane Bumpers

injection, vacuum, septum, linac

2575

B. Balhan, C. Baud, J.C.C.M. Borburgh, M. Hourican
CERN, Geneva, Switzerland

In the framework of the LIU project and the connection from LINAC4 to PS Booster, the 160 MeV H⁻ beam will be injected horizontally into the PSB by means of one charge-exchange injection system for each PSB ring. A set of four outside vacuum pulsed dipole magnets (BSW) creating the required injection bump has been designed and built. The dynamic requirements for the bump ramp down determine, to a large extent, the field homogeneity due to the eddy currents induced in the corrugated Inconel vacuum chamber. Magnetic simulations were performed to determine the field harmonics during bump ramp down, and the results subsequently used for the dynamic tracking of the beam during injection. The mechanical design and construction of the magnets will be briefly outlined, and the article will conclude with the magnetic measurements of the magnets. The magnetic performance of the as built magnets will be compared with the simulations and the influence of the vacuum chambers on the magnetic field will be quantified.

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WEPMF089

Measurements of Electromagnetic Properties of Ferrites as a Function of Frequency and Temperature

kicker, impedance, injection, coupling

2592

A. Chmielinska, M.J. Barnes, F. Caspers, B.K. Popovic, C. Vollinger
CERN, Geneva, Switzerland

Fast kicker magnets are used to inject beam into and extract beam out of the CERN accelerator rings. These kickers are often ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. The interaction of the beam with the resistive part of the longitudinal beam coupling impedance leads to power dissipation and heating of different elements in the accelerator ring. In particular, power deposition in the kicker magnets can be a limitation: if the temperature of the ferrite yoke exceeds the Curie temperature, the beam will not be properly deflected. In addition, the imaginary portion of the beam coupling impedance contributes to beam instabilities. A good knowledge of electromagnetic properties of materials up to GHz frequency range is essential for a correct impedance evaluation. This paper presents the results of transmission line measurements of complex initial permeability and permittivity for different ferrite types. We present an approach for deriving electromagnetic properties as a function of both frequency and temperature; this information is required for simulating ferrite behaviour under realistic operating conditions.

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WEPMG001

Engineering Design and Prototyping of the New LIU PS Internal Beam Dumps

vacuum, interface, proton, operation

2600

G. Romagnoli, J.A. Briz Monago, M.E.J. Butcher, M. Calviani, D.G. Cotte, Y. C. Coutron, J.J. Esala, E. Grenier-Boley, J. Hansen, A. Huschauer, A. Masi, F.-X. Nuiry, D. Steyart, V. Vlachoudis
CERN, Geneva, Switzerland

For the LHC Injectors Upgrade (LIU) at CERN, the two Proton Synchrotron (PS) internal dumps are redesigned and upgraded for the new high intensity/brightness beams. The dumps are installed as active elements in the lattice in straight sections between the main bending magnets. The dumps are moved into the beam when requested by operation and shave the circulating beam turn by turn stopping the beam after about 6 ms. The shaving induces a very localized beam energy deposition on the dump surface in a thickness of tens of microns. A completely new approach has been developed with FLUKA to simulate beam shaving, coupled with ANSYS to define a new dump core design. This paper presents the design of the dump based on operational constraints such as cycling 200 000 times per year for 20 years, limited access for maintenance or reaching the beam trajectory in 150 ms. These constraints had a major impact on the technological choices. The new dump core is made of a low-density graphite block followed by a denser copper alloy (CuCr1Zr) one. Water circuits, bonded with Hot Isostatic Pressing, are cooling the core in ultra-high vacuum. The core is moved by a spring-based actuation mechanism.

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WEPMG002

Beam Dump Facility Target: Design Status and Beam Tests in 2018

target, radiation, operation, experiment

2604

E. Lopez Sola, O. Aberle, P. Avigni, L. Bianchi, J. Busom, M. Calviani, M. Casolino, J.P.C. Espadanal, M.A. Fraser, S. Girod, B. Goddard, D. Grenier, M. Guinchard, C. Heßler, R. Illan Fiastre, R. Jacobsson, M. Lamont, A. Ortega Rolo, B. Riffaud, G. Romagnoli, L. Zuccalli
CERN, Geneva, Switzerland

The Beam Dump Facility (BDF) Project, currently in its design phase, is a proposed general-purpose fixed target facility at CERN, dedicated to the Search for Hidden Particles (SHiP) experiment in its initial phase. At the core of the installation resides the target/dump assembly, whose aim is to fully absorb the high intensity 400 GeV/c SPS beam and produce charmed mesons. In addition to high thermo-mechanical loads, the most challenging aspects of the proposed installation lie in very high energy and power density deposition that are reached during operation. In order to validate the design of the BDF target, a scaled prototype is going to be tested during 2018 in the North Area at CERN, upstream the existing beryllium primary targets. The prototype testing under representative beam scenarios will allow having an insight of the material response in an unprecedented regime. Online monitoring and an extensive Post Irradiation Experimental (PIE) campaign are foreseen. The current contribution will detail the design and handling aspects of the innovative Target Complex as well as the design of the BDF target/dump core and the design and construction of the prototype target assembly.

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WEPMG003

Analysis and Operational Feedback of the New High-Energy Beam Dump in the CERN SPS

operation, MMI, shielding, monitoring

2608

A. Perillo-Marcone, M. Calviani, R. Illan Fiastre, P. Rios Rodriguez, G. Romagnoli
CERN, Geneva, Switzerland

The CERN Super Proton Synchrotron (SPS) high-energy internal dump (TIDVG) is used to intercept beam dumps from 10².2 to 450 GeV. An inspection in 2013 revealed significant beam induced damage to the aluminium absorbing block, resulting in operational limitations to minimize the risk of reproducing this phenomenon. Additionally, in 2016 a vacuum leak was detected in the dump assembly, which imposed further limitations, i.e., a reduction of the beam intensity that could be dumped. In the winter stop of 2016-2017, a new version of the TIDVG (featuring several design modifications) was installed. This paper analyses the performance of the dump observed during the commissioning period and subsequent operation in 2017 of the most recent installed version of the TIDVG. The temperature measurements recorded during this time were used to benchmark numerical models that allow predicting the performance of the dump under different conditions. After several iterations, a good agreement between simulations and real measurements was obtained; resulting in numerical models that can produce reliable results for this and other devices with similar design.

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WEPMG004

Design of the Future High Energy Beam Dump for the CERN SPS

operation, shielding, dumping, kicker

2612

S. Pianese, J.A. Briz Monago, M. Calviani, D. Grenier, P.B. Heckmann, J. Humbert, R. Illan Fiastre, A. Perillo-Marcone, G. Romagnoli, S. Sgobba, D. Steyart, V. Vlachoudis
CERN, Geneva, Switzerland

The future CERN Super Proton Synchrotron (SPS) internal dump (Target Internal Dump Vertical Graphite, known as TIDVG#5), to be installed during CERN's Long Shutdown 2 (2019-2020), will be required to intercept beam dumps from 26 to 450 GeV, with increased intensity and repetition rates with respect to its predecessor (TIDVG#4). The beam power to be managed by the dump will increase by approximately a factor of four; resulting in new challenges in terms of design in order to fulfil the highly demanding specification, which is based on guaranteeing a good performance of the machine with little or no limitations imposed by this device. This paper presents the proposed design, including material selection, manufacturing techniques and thermo-mechanical simulations under different operational scenarios expected during the lifetime of the device.

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WEPMK002

Longitudinal Impedance Analysis of an Upgraded LHC Injection Kicker Magnet

impedance, kicker, injection, vacuum

2628

V. Vlachodimitropoulos, M.J. Barnes, L. Vega Cid, W.J.M. Weterings
CERN, Geneva, Switzerland

Prior to Long Shutdown 1 (LS1) one of the LHC injection kickers (MKIs) occasionally exhibited high temperatures leading to significant turnaround times. After a successful impedance mitigation campaign during LS1, the MKI ferrite yokes have remained below their Curie point and have not limited LHC's availability. However, for HL-LHC operation the MKI yokes are expected to exceed their Curie temperatures after long physics runs. To ensure uninterrupted future HL-LHC operation, a modified beam screen design, relocating some of the heat load to more easily cooled parts, and a suitable cooling system are under development as the current baseline for the HL-LHC upgrade of the MKIs. An upgraded beam screen providing such relocation has been designed, simulated and compared to the existing model. To validate simulations, two longitudinal beam coupling impedance measurement techniques have been used and the results are compared to predictions. The modified beam screen was implemented in an upgraded MKI installed in the LHC during the Year End Technical Stop (YETS) 2017/18.

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WEPML002

Design of 650 MHz Tuner for PIP-II Project

cavity, interface, experiment, linac

2671

Y.M. Pischalnikov, S. Cheban, J.C. Yun
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Proton Improvement Plan (PIP) II project at Fermilab is a proton driver linac which will use of five different cavity geometries including a 650 MHz 5-cell elliptical cavities that will operate in RF-pulse mode. Detuning of these cavities by Lorentz Forces will be large and strongly depend of the stiffness of the cavity's tuner. First prototype tuner built and tested warm [1,2]. Measured stiffness of the prototype tuner was below 30kN/mm instead of expected from simulation 70kN/mm [2]. Significant effort has been invested into understanding discrepancy between simulation and experimental data that led to newest tuner design. Updated 'dressed cavity-helium vessel-tuner' model provided consistent results between ANSYS simulations and experiment results. Modified tuner design and analysis in limitations for overall 'cavity/tuner system' stiffness will be presented.

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WEPML006

Modified Slow Tuner Design for Cavity 1 Inside LCLS II Cryomodules

cavity, cryomodule, interface, SRF

2684

Y.M. Pischalnikov, T.T. Arkan, S. Cheban, J.P. Holzbauer, J.A. Kaluzny, Y.O. Orlov, J.C. Yun
Fermilab, Batavia, Illinois, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
Initial LCLS-II cryomodule testing at Fermilab showed microphonics on the furthest upstream cavity (number 1) at least factor 2 larger than on the rest of the cavities. Testing indicated that this was a difference in the mechanical support of cavity 1, not a local acoustic source. Further investigation pointed to the upstream beam-pipe of the cavity 1. The upstream cavity flange has a solid spool piece connection to the beamline gate valve unlike the other cavities, which all connect through bellows. The gate valve's weight is supported by sliding system (free in z-axis) connected to large diameter Helium gas return pipe. The tuner design was modified to transform interface between cavity#1 and gate valve. Arms of the tuner for cavity 1 were extended and became the support structure for gate valve, eliminating the connection to the helium return pipe. Modification of the tuner design and results in microphonics mitigations will be presented.

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WEPML010

Operation Regime Analysis of Conduction Cooled Cavities Through Multi-Physics Simulation

cavity, operation, SRF, niobium

2697

R.A. Kostin, R. Dhuley, M.G. Geelhoed, R.D. Kephart, T.K. Kroc, O.V. Prokofiev, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA

Funding: Department of Energy
Euclid Techlabs in collaboration with Fermilab IARC (Batavia, IL) is developing industrial superconducting 10MeV electron linac. Conduction cooling is used for cooling instead of liquid helium bath to simplify linac maintenance. The cavity linked to commercially available cryo-cooler cold head through highly conductive aluminium strips. However, this solution raises a problem of contact thermal resistance. This paper shows some results of Comsol multyphysics simulations of the cavity cooling by AL strips. Some insight was obtained on the acceptable range of contact resistance. Operation regimes were obtained at different accelerating gradients and cavity temperatures. The results of simulation are presented and discussed.

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WEPML011

Garnet Ring Measurements for the Fermilab Booster 2nd Harmonic Cavity

cavity, booster, controls, solenoid

2700

R.L. Madrak, J.E. Dey, K.L. Duel, J. Kuharik, A.V. Makarov, W. Pellico, J. Reid, G.V. Romanov, M. Slabaugh, D. Sun, C.-Y. Tan, I. Terechkine
Fermilab, Batavia, Illinois, USA

A perpendicularly biased tuneable 2nd harmonic cavity is being constructed for use in the Fermilab Booster. The cavity's tuner uses National Magnetics AL800 garnet as the tuning media. For quality control, the magnetic properties of the material and the uniformity of the properties within the tuner must be assessed. We describe two tests which are performed on the rings and on their corresponding witness samples.

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WEPML022

3.9 GHz Power Coupler Design and Tests for LCLS-II Project

cavity, resonance, cryomodule, diagnostics

2727

N. Solyak, I.V. Gonin, C.J. Grimm, E.R. Harms, T.N. Khabiboulline, A. Lunin, O.V. Prokofiev, G. Wu
Fermilab, Batavia, Illinois, USA

LCLS-II linac requires two 3.9 GHz cryomodules (eight cavities per CM), operating up to 16MV/m in cw regime. Fermilab has designed and built few prototypes of the cavity and auxiliaries and tested them at the vertical and horizontal cryostats. Fundamental power coupler, based on existing design (FLASH, XFEL) was redesign for 2kW average power. We built three prototypes and tested them at room temperature test stand. One coupler was assembled on the cavity and tested at horizontal cryostat as part of design verification program. Test results and comparison with simulations are discussed in this paper.

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WEPML039

Design of the Two-Gap Superconducting Re-Buncher

cavity, heavy-ion, linac, proton

2779

M. Gusarova, W.A. Barth, S. Yaramyshev
MEPhI, Moscow, Russia
W.A. Barth, S. Yaramyshev
GSI, Darmstadt, Germany
W.A. Barth, M. Miski-Oglu
HIM, Mainz, Germany
M. Basten, M. Busch
IAP, Frankfurt am Main, Germany
M. Gusarova
JINR, Dubna, Moscow Region, Russia

A new design of a spoke cavity for low relative velocities of heavy ions has been elaborated. Simulation results for a 2-gap spoke cavity with a resonance frequency of 216.816 MHz and a relative velocity of 0.07с are presented.

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WEPML043

RF Simulations of the Injector Section from CH8 to CH15 for MYRRHA

cavity, impedance, resonance, MMI

2790

P. Müller, M. Busch, H. Hähnel, K. Kümpel, D. Mäder, N.F. Petry, H. Podlech
IAP, Frankfurt am Main, Germany

Funding: Work supported by the EU Framework Programme H2020 662186 (MYRTE) and HIC for FAIR
MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) is the first prototype of an accelerator driven nuclear reactor dealing with the transmutation of long-living nuclear waste. Beam quality and reliability are crucial for the reactor. The injector design is done by IAP, Goethe-University, and has been adapted to the final magnet design and voltage distributions. The energy section from 5.87 MeV up to 16.6 MeV has been changed to normal conducting CH cavities as in the lower energy part of the injector. For beam adjustment a 5-gap CH cavity rebuncher at 5.87 MeV as well as two doublet magnets forming the new MEBT-2 section between CH7 and CH8 have been added. Starting parameters for the RF simulations have been given by beam dynamics results calculated with LORASR. RF simulations of these structures consisting of flatness and tuning optimizations will be presented within this contribution.

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WEPML044

Design of HOM Couplers for Superconducting 400 MHz RF Cavities

HOM, cavity, collider, proton

2793

N.F. Petry, M. Busch, K. Kümpel, O. Meusel, H. Podlech
IAP, Frankfurt am Main, Germany

The Future Circular Collider (FCC) is one possible future successor of the Large Hadron Collider (LHC). The proton-proton collider center-of-mass collision energy is set to 100 TeV with a beam current of 0.5 A. To reach this goal a stable acceleration is critical and therefore higher order modes (HOM) need to be damped. To avoid a high power level in the HOM dampers, further described as couplers, the loaded Q-factor should be below 1000 for the cavity with mounted HOM couplers. Besides a low Q-factor the R/Q value should also be in the range of 1 Ω or below. Two different types of couplers are used to achieve a high damping. The two types are a narrowband Hook-type HOM coupler and a broadband Probe-type HOM coupler. The recent results of the design of the HOM couplers attached to a superconducting 400 MHz RF cavity will be presented.

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WEPML048

HOM Power Levels in the BESSY VSR Cold String

HOM, cavity, SRF, GUI

2808

A.V. Tsakanian, T. Flisgen
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
H.-W. Glock, J. Knobloch, A.V. Vélez
HZB, Berlin, Germany

The BESSY VSR upgrade of the BESSY II light source represents a novel approach to simultaneously store long (ca. 15ps) and short (ca. 1.7ps) bunches in the storage ring. This challenging goal requires installation of four new SRF cavities (2x1.5 GHz and 2x1.75 GHz) in one module for installation in a single straight. These cavities are equipped with strong waveguide HOM dampers necessary for stable operation. The expected HOM power and spectrum has been analyzed for the complete cold string. The cold string is a combination of various elements such as SRF cavities, bellows with and without shielding, warm HOM beampipe absorbers and UHV pumping domes. The presented study is performed for various BESSY VSR bunch filling patterns with 300 mA beam current. The contribution of each component to the total HOM power is presented. In addition the optimization of different cavity arrangements in the module is performed in order to reach the optimal operation conditions with equally distributed power levels along the string and tolerable beam coupling impedance.

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WEPML049

The Challenge to Measure nΩ Surface Resistance on SRF Samples

SRF, quadrupole, pick-up, cavity

2812

S. Keckert, T. Junginger, J. Knobloch, O. Kugeler
HZB, Berlin, Germany
T. Junginger
Lancaster University, Lancaster, United Kingdom

Systematic research on fundamental limits of superconducting materials for SRF applications and their intrinsic material properties relevant for use in an accelerator requires studies in a wide parameter space of temperature, RF field and frequency. The Quadrupole Resonator at HZB enables precision measurements on planar samples at temperatures of 1.8 K to >20 K, RF fields of up to 120 mT, and frequencies of 420 MHz, 850 MHz and 1285 MHz. In the past years the capabilities of the setup were studied intensively and developed further. Sources of systematic errors, such as microphonics or misalignment have been identified and eliminated. In this contribution the current status of the QPR and its systematic limitations are discussed.

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WEPML069

Fast Kicker and Pulser R&D for the HEPS on-Axis Injection System

kicker, injection, impedance, vacuum

2846

H. Shi, J. Chen, Z. Duan, L. Huo, P. Liu, X.L. Shi, G. Wang, L. Wang, N. Wang
IHEP, Beijing, People's Republic of China

The HEPS plans to adopt on-axis injection scheme because the dynamic aperture of machine is not large enough for off-axis injection for its baseline 7BA lattice design. A sets of super fast kicker and pulser of ±15kV amplitude, 15ns pulse bottom width are needed for bunch spacing of 10ns to minimize perturbation on adjacent bunches. To achieve these requirement, a multifaceted R&D program including the strip-line kicker and HV pulser, was initiated last 2 years. So far, the prototype development of a 750mm long strip-line kicker and a DSRD pulser was completed and the preliminary test results show they can meet the baseline requirement of the HEPS.

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THXGBD1

The Upgrade of the Advanced Photon Source

lattice, feedback, controls, cavity

2872

M. Borland, M. Abliz, N.D. Arnold, T.G. Berenc, J.M. Byrd, J.R. Calvey, J.A. Carter, J. Carwardine, H. Cease, Z.A. Conway, G. Decker, J.C. Dooling, L. Emery, J.D. Fuerst, K.C. Harkay, A.K. Jain, M.S. Jaski, P.S. Kallakuri, M.P. Kelly, S.H. Kim, R.M. Lill, R.R. Lindberg, J. Liu, Z. Liu, J. Nudell, C.A. Preissner, V. Sajaev, N. Sereno, X. Sun, Y.P. Sun, S. Veseli, J. Wang, U. Wienands, A. Xiao, C. Yao
ANL, Argonne, Illinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

After decades of successful operation as a 7-GeV synchrotron radiation source, the Advanced Photon Source is pursing a major upgrade that involves replacement of the storage ring with an ultra-low emittance multi-bend achromat design. Using a seven-bend hybrid multi-bend achromat with reverse bending magnets gives a natural emittance of 42 pm operated at 6 GeV. The x-ray brightness is predicted to increase by more than two orders of magnitude. Challenges are many, but appear manageable based on thorough simulation and in light of the experience gained from world-wide operation of 3^\text{rd}-generation light sources. The upgraded ring will operate in swap-out mode, which has allowed pushing the performance beyond the limits imposed by conventional operation.

Slides THXGBD1 [14.684 MB]

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THXGBE1

6D Beam Measurement, Challenges and Possibilities

rfq, experiment, quadrupole, linac

2890

A.V. Aleksandrov, S.M. Cousineau, A.P. Zhukov
ORNL, Oak Ridge, Tennessee, USA
B.L. Cathey
ORNL RAD, Oak Ridge, Tennessee, USA

A system to measure the full 6D beam parameters (not 3x2D) has been built at the SNS RFQ test stand. Such a measurement will allow detailed analysis of the beam physics from a properly measured input term. This invited provides an overview of the principles and design of this system, and reports on status and results.

Slides THXGBE1 [4.471 MB]

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THYGBD2

Results of UFO Dynamics Studies with Beam in the LHC

experiment, emittance, proton, beam-losses

2914

B. Lindstrom, A. Apollonio, P. Bélanger, M. Dziadosz, A.A. Gorzawski, L. K. Grob, E.B. Holzer, A. Lechner, R. Schmidt, M. Valette, D. Valuch, D. Wollmann
CERN, Geneva, Switzerland

Micrometer sized particles entering the LHC beam (the so-called Unidentified Falling Objects or UFOs) are a known cause of localized beam losses since the beginning of high intensity beam operation, however the origin of these particles is not fully known. Their effect limits LHC availability by causing premature dumps due to excessive beam losses and occasionally even magnet quenches. This could become an important limitation for future accelerators such as the High Luminosity upgrade of the LHC (HL-LHC) and the Future Circular Collider (FCC). The dynamics of these UFOs was investigated in two dedicated experiments. In the first experiment, it was shown that the transverse movements of these particles can be studied by observing bunch-by-bunch losses from bunches with different horizontal and vertical emittances. In the second experiment, UFO-like events around the 16L2 interconnect in the LHC, which has seen intense UFO activity in 2017, were studied with the above method. This paper summarizes the results of both experiments.

Slides THYGBD2 [1.357 MB]

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THYGBE4

Early Phase 2 Results of LumiBelle2 for the SuperKEKB Electron Ring

luminosity, background, electron, photon

2934

S. Di Carlo, P. Bambade, D. Jehanno, V. Kubytskyi, C.G. Pang, Y. Peinaud, C. Rimbault
LAL, Orsay, France

We report on the early SuperKEKB Phase 2 operations of the fast luminosity monitor (LumiBelle2 project). Fast luminosity monitoring is required by the dithering feedback system, which is used to stabilize the beam in the presence of horizontal vibrations. In this report, we focus on the operations related to the electron side of LumiBelle2. Diamond sensors are located 30 meters downstream of the IP, just above, beside, and below the electron beam pipe. During early Phase 2, the sensors are used to measure the background, arising from beam-gas scattering. We present the hardware design, the detection algorithm, and the analysis of the background measurements taken up-to-date. The results are then compared with a detailed simulation of the background, in order to well understand the physical processes involved. The simulation is performed using SAD for generation and tracking purposes, while Geant4 is used to calculate the energy deposition in the diamond sensors.

Slides THYGBE4 [3.091 MB]

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THPAF005

Simulations of Modulator for Coherent Electron Cooling

electron, bunching, plasma, quadrupole

2953

J. Ma, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Highly resolved numerical simulations have been performed using the code SPACE for the modulator, the first section of the Coherent electron cooling (CeC) device installed in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Simulation results have been benchmarked with analytical solution using uniform electron beam with realistic thermal velocities. Electron bunches with Gaussian distribution and quadrupole field with realistic settings have been applied in the simulations to predict the modulation process and final bunching factors induced by ions with reference and off-reference energies in the CeC experiment at BNL RHIC.

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THPAF006

Simulations of Cooling Rate and Diffusion for Coherent Electron Cooling Experiment

electron, FEL, kicker, bunching

2957

J. Ma, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Start-to-end numerical simulations have been performed using the code SPACE and GENESIS for the single pass of gold ions through the coherent electron cooling (CeC) device installed in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). Cooling rate of CeC experiment has been predicted using off-reference energy ions in a finite Gaussian electron beam through a realistic beam-line, in which settings of quadrupoles and free-electron laser (FEL) device are relevant to BNL RHIC.

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THPAF010

Reduction of Coherent Betatron Oscillations Using RF Electric Fields in the Fermilab Muon g-2 Experiment

dipole, quadrupole, experiment, betatron

2961

O. Kim, S. Hacıömeroğlu, Y.I. Kim, Y.K. Semertzidis
CAPP/IBS, Daejeon, Republic of Korea
Y.F. Orlov
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

The Fermilab Muon g-2 experiment aims to measure the muon anomalous magnetic moment with a 140 parts-per-billion precision to investigate the greater than 3 standard deviation difference between the Standard Model prediction and the previous measurement by the BNL Muon g-2 experiment. The coherent betatron oscillation (CBO) beam effects must be corrected for in the decay-positron time spectra fits used in high precision muon storage ring based anomalous magnetic moment measurements. This MC simulation study indicates that the application of radio frequency (RF) electric fields to the muon storage ring beam can reduce the CBO amplitude by up to a factor of 10, as well to increase the symmetry of the beam phase space. This is achieved by correcting the mismatched oscillation phases between the high and low momentum muon populations by modulating the muon beam betatron oscillation frequencies with off-resonance RF fields.

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THPAF012

The Influence of Chromaticity on Transverse Single-Bunch Instability in the Booster of HEPS

booster, damping, injection, radiation

2968

H.S. Xu, N. Wang
IHEP, Beijing, People's Republic of China

The study of the transverse single-bunch instability has been carried out for the HEPS booster to double check whether the required single-bunch charge can be achieved. The chromaticity has been varied in our study to see how the threshold changes accordingly. Usually, the slightly positive chromaticity is expected for stabilizing the beam. However, our simulations show that the single-bunch threshold current drops significantly when the chromaticity becomes non-zero. We present the simulation methods and results in details in this paper. The analysis of the simulation results is also presented.

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THPAF015

Beam Tracking Studies of Electron Cooling in ELENA

electron, proton, antiproton, emittance

2975

B. Veglia, J.R. Hunt, J. Resta-López, V. Rodin, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.R. Hunt, J. Resta-López, V. Rodin, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom

Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 721559.
The Extra Low ENergy Antiproton storage ring (ELENA), which is currently being commissioned at CERN, will further decelerate antiprotons extracted from the Antiproton Decelerator (AD) from 5.3 MeV to energies as low as 100 keV. It will provide high quality beams for the antimatter experiments located within the AD hall. At such low energies, it is important to correctly evaluate the long term beam stability. To provide a consistent explanation of the different physical phenomena affecting the beam, tracking simulations have been performed and the results will be presented in this contribution. These include electron cooling and various scattering effects under realistic conditions. The effects of several imperfections in the electron cooling process will also be discussed. In addition, analytical approximations of the temporal variation of emittance under these conditions will be presented, and compared with numerical simulation results.

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THPAF016

3D Tracking Methods in a GEANT4 Environment Through Electrostatic Beamlines

quadrupole, experiment, proton, antiproton

2979

J.R. Hunt, J. Resta-López, V. Rodin, B. Veglia, C.P. Welsch
The University of Liverpool, Liverpool, United Kingdom
J.R. Hunt, J. Resta-López, V. Rodin, B. Veglia, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Funding: Work supported by the EU under Grant Agreement 721559 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
Due to the relatively infrequent use of electrostatic beamline elements compared with their magnetic counterparts, there are few particle tracking codes which allow for the straightforward implementation of such beamlines. In this contribution, we present 3D tracking methods for beamlines containing electrostatic elements utilising a modified version of the Geant4 based tracking code 'G4beamline'. In 2020 transfer lines will begin transporting extremely low energy (100 keV) antiproton beams from the Extra Low Energy Antiproton (ELENA) ring to the antimatter experiments at CERN. Electrostatic bending and focusing elements have been chosen for the beamlines due to their mass independence and focusing efficiency in the low energy regime. These beamlines form the basis of our model which is benchmarked against simplified tracking simulations. Realistic beam distributions obtained via tracking around ELENA in the presence of collective effects and electron cooling will be propagated along the optimised 3D transfer model to achieve the best beam quality possible for the experiments.

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THPAF017

Improvement of RF Field Phase and Amplitude Errors Simulations in TraceWin Code

cavity, linac, diagnostics, beam-losses

2983

D. Uriot
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France

Funding: This work is supported by the European Atomic Energy Community's (EURATOM) H2020 Programme under grant agreement n°662186 (MYRTE project)
RF field phase and amplitude errors are usually not correctly simulated and it is a serious problem especially when in high intensity linear accelerators, the main losses are due to particle leaving the beam acceptance. This new development implemented in TraceWin fixes this issue. The objective is to improve the longitudinal beam dynamics simulation methods, by including more close-to-real models for the cavities tuning procedure. By this way, clear distinction should be done between static and dynamic errors and longitudinal diagnostics accuracy can be clearly defined according to beam dynamics results.

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THPAF021

Start to End Simulation of the CBETA Energy Recovery Linac

linac, lattice, optics, space-charge

2993

W. Lou, A.C. Bartnik, J.A. Crittenden, C.M. Gulliford, G.H. Hoffstaetter, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
J.S. Berg, S.J. Brooks, F. Méot, D. Trbojevic, N. Tsoupas
BNL, Upton, Long Island, New York, USA
C.E. Mayes
SLAC, Menlo Park, California, USA

Funding: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.
CBETA is an energy recovery linac accelerating from 6 MeV to 150 MeV in four linac passes, using a single return line accepting all energies from 42 MeV to 150 MeV. We simulate a 6-dimensional particle distribution from the injector through the end of the dump line. Space charge forces are taken into account at the low energy stages. We compare results using field maps to those using simpler magnet models. We introduce random and systematic magnet errors to the lattice, apply an orbit correction algorithm, and study the impact on the beam distribution.

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THPAF022

Beam Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery Linac Test Accelertor

HOM, cavity, lattice, dipole

2996

W. Lou, G.H. Hoffstaetter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL-FFAG Test Accelerator (CBETA). To be built at Cornell Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) fields are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). We would present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current.

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THPAF025

Progress in Measurement and Modeling of Electron Cloud Effects at CesrTA

electron, dipole, emittance, positron

3007

S. Poprocki, S.W. Buechele, J.A. Crittenden, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467 and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
The synchrotron-radiation-induced buildup of low-energy electron densities in positron and proton storage rings limits performance by causing betatron tune shifts and incoherent emittance growth. The Cornell Electron Storage Ring (CESR) Test Accelerator project includes extensive measurement and modeling programs to quantify such effects and apply the knowledge gained to the design of future accelerator projects. We report on improved measurements of betatron tune shifts along a train of positron bunches, now accurate in both horizontal and vertical planes. Improved electron cloud buildup modeling uses detailed information on photoelectron production properties obtained from recently developed simulations and successfully describes the measurements after determining ring-wide secondary-yield properties of the vacuum chamber by fitting the model to data with a multi-objective optimizer. Cloud splitting in dipole magnetic fields is seen to be the source of horizontal tune shifts decreasing at higher bunch populations.

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THPAF026

Modeling Studies for Synchrotron-Radiation-Induced Electron Production in the Vacuum Chamber Walls at CesrTA

photon, electron, vacuum, site

3011

S. Poprocki, J.A. Crittenden, D. L. Rubin, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work is supported by the US National Science Foundation PHY-0734867, PHY-1002467 and the US Department of Energy DE-FC02-08ER41538, DE-SC0006505.
We report on calculations of electron production by synchrotron radiation absorbed in the vacuum chamber walls of the Cornell Electron Storage Ring (CESR). These electrons are the source of electron clouds which limit the performance of storage rings by causing betatron tune shifts, instabilities and emittance growth. Until now, cloud buildup modeling codes have used ad hoc models of the production of the seed electrons. We have employed the photon scattering code Synrad3D to quantify the pattern of absorbed photons around the CESR ring, including the transverse distribution on the wall of the beam-pipe. These distributions in absorbed photon energy and incident angle are used as input to Geant4-based simulations of electron emission from the walls. The average quantum efficiency is found to vary dramatically with the location of the absorption site, owing to the distribution in impact energies and angles. The electron production energy spectrum plays an important role in the modeling of electron cloud buildup, where the interplay of production energy and acceleration by the beam bunches determines the time structure and multipacting characteristics of the cloud.

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THPAF032

Simulation Study of an RF Injector for the LWFA Configuration at EuPRAXIA

linac, injection, plasma, emittance

3025

J. Zhu, R.W. Aßmann, A. Ferran Pousa, B. Marchetti, P.A. Walker
DESY, Hamburg, Germany

The Horizon 2020 Project EuPRAXIA (EuropeanPlasma Research Accelerator with eXcellence In Applications) aims at producing a design report of a highly compact and cost-effective European facility with multi-GeV electron beams using a plasma accelerator. LWFA with external injection from an RF accelerator is one of the most promising configurations. In order to achieve the goal parameters for the 5 GeV, 30 pC electron beam at the entrance of the undulator, a high-quality electron beam with bunch length of less than 10 fs (FWHM) and matched beta functions (~1 mm) at the plasma entrance is required. In addition, from the compactness point of view, the injection energy is desired to be as low as possible. A hybrid compression scheme is considered in this paper and a detailed start-to-end simulation is presented.

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THPAF034

Studies of Horizontal Instabilities in the CERN SPS

octupole, optics, damping, impedance

3032

M.S. Beck, H. Bartosik, M. Carlà, K.S.B. Li, G. Rumolo, M. Schenk
CERN, Geneva, Switzerland
U. van Rienen
Rostock University, Faculty of Engineering, Rostock, Germany

In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations.

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THPAF041

Uncontrolled Longitudinal Emittance Blow-Up during RF Manipulations in the CERN PS

impedance, cavity, emittance, controls

3056

A. Lasheen, H. Damerau, G. Favia
CERN, Geneva, Switzerland

The CERN Proton Synchrotron (PS) determines the basic bunch spacing for the Large Hadron Collider (LHC) by means of rf manipulations. Several rf systems in a frequency range from 2.8 MHz to 200 MHz are available for beam acceleration and manipulations. Each of the six bunches injected from the PS Booster is split in several steps into 12 bunches spaced by 25 ns, yielding a batch of 72 bunches at transfer to the Super Proton Synchrotron (SPS). In the framework of the LHC Injector Upgrade (LIU) project the bunch intensity must be doubled. However, with most of the planned upgrades already in place this intensity has not yet been achieved due to collective effects. One of them is uncontrolled longitudinal emittance blow-up during the bunch splittings. In this contribution, measurements of the blow-up during the splitting process are presented and compared with particle simulations using the present PS impedance model. Beam-based measurements of the impedances of the rf cavities have been performed. They revealed that to reproduce the instability an additional impedance source is required in the PS impedance model.

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THPAF051

Beam Impedance Evaluation for CERN PS Gate Valves by Simulation and Benchmark Measurement

impedance, wakefield, resonance, coupling

3080

B.K. Popovic, C. Vollinger
CERN, Geneva, Switzerland

The CERN High Luminosity LHC project calls for a doubling of beam intensity which requires a clear identification of possible longitudinal instability sources in the injector chain. This requirement yields the need to further improve the longitudinal impedance model for the Proton Synchrotron (PS). In this impedance model it is necessary to include not only obvious impedance sources, such as RF cavities and kickers but also seemingly innocuous elements like certain vacuum components. Individually these vacuum elements would give only a small impedance contribution, however, due to the large number of these elements in the machine, their resultant combined impedances impact the overall impedance budget. This paper presents the electromagnetic simulation analysis of the PS sector gate valves along with EM measurements confirming the simulation model. These measurements are especially crucial in this case since no complete mechanical model or drawings are available and assumptions had to be made regarding its interior mechanical structure.

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THPAF053

Lower-Harmonic RF System in the CERN SPS

emittance, impedance, cavity, proton

3087

J. Repond, H. Damerau, A. Lasheen, E.N. Shaposhnikova
CERN, Geneva, Switzerland

Significant beam losses increasing with intensity are observed at capture and along the SPS flat bottom for the LHC-type proton beam. The intensity should be doubled for HL-LHC and high losses may be a major performance limitation. Bunches extracted from the PS, the SPS injector, are produced in a 40 MHz RF system applying a bunch rotation at the end of the cycle and therefore cannot be perfectly matched to the 200 MHz SPS RF bucket. The possibility of using a lower harmonic additional RF capture system in the SPS was already proposed after the LEP era in preparation for transfer of the LHC beam but the bunch rotation was the preferred solution, since the induced voltage in the SPS 200 MHz RF system would be too large to ensure stability in a low harmonic system without mitigation measures. However, the use of the upgraded one-turn feedback and the 200 MHz RF system as a Landau cavity could help to improve stability. The feasibility of this scenario to reduce capture losses in the SPS is analysed and presented in this paper. The choice of an optimum RF frequency and voltage is also discussed. The transfer to the main 200 MHz is simulated using a realistic bunch distribution.

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THPAF055

Space Charge Studies on LEIR

resonance, space-charge, emittance, lattice

3095

Á. Saá Hernández, H. Bartosik, N. Biancacci, S. Hirlaender, A. Huschauer, D. Moreno Garcia
CERN, Geneva, Switzerland

The performance of the CERN Low Energy Ion Ring with electron cooled ion beams is presently limited by losses occurring once the beam has been captured in the RF buckets. An intense machine study program was started by the end of 2015 to mitigate the losses and improve the performance of the accelerator. The measurements pointed to the interplay of direct space charge forces and excited betatron resonances as the most plausible driving mechanism of these losses. In this paper, we present the systematic space-charge measurements performed in 2017 and compare them to space-charge tracking simulations based on an adaptive frozen potential.

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THPAF057

Instability Observations in the Large Hadron Collider During Run 2

coupling, operation, electron, hadron

3099

L.R. Carver, D. Amorim, S. A. Antipov, N. Biancacci, X. Buffat, G. Iadarola, K.S.B. Li, E.H. Maclean, L. Mether, E. Métral, B. Salvant, M. Schenk
CERN, Geneva, Switzerland
L. Mether, M. Schenk
EPFL, Lausanne, Switzerland

Instabilities of many different types and characteristics have been observed in the LHC during Run 2. The origin of these instabilities come from a variety of stabilising and destabilising mechanisms. Efforts to understand these instabilities and prevent their occurrence has improved the performance of the LHC in all stages of the machine cycle. This paper aims to give an overview into some of the instability observations and details the operational steps to prevent them.

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THPAF062

Impact of Superconducting Magnet Protection Equipment on the Circulating Beam in HL-LHC

dipole, quadrupole, shielding, experiment

3115

M. Valette, L. Bortot, A.M. Fernandez Navarro, B. Lindstrom, M. Mentink, R. Schmidt, E. Stubberud, A.P. Verweij, D. Wollmann
CERN, Geneva, Switzerland
E. Ravaioli
LBNL, Berkeley, California, USA

Funding: Work supported by the HL-LHC project.
The new superconducting quadrupole and dipole magnets for the High Luminosity LHC (HL-LHC) will rely on quench heaters or Coupling-Loss Induced Quench (CLIQ) units or a combination of both to protect the magnet coils in case of a quench. After the detection of a quench, the quench heater power supplies will discharge currents of several hundreds of amperes into the quench heater strips glued to the coils, and the CLIQ units will discharge an oscillating current in the order of 1~kA directly into the coils. These currents can have a significant effect on the circulating beam if the discharge occurs before the beam is dumped. In the HL-LHC inner triplet quadrupole magnets and 11 T dipole magnets, which will be installed in the collimation region dispersion suppressor, this effect will even be stronger due to the larger number of quench heaters and use of CLIQ units (triplet magnets only) as well as due to the greater value of beta function in comparison with the present LHC. In this paper, the expected effects of quench heater and CLIQ discharges on the circulating beam are summarized, and several mitigation methods are proposed and evaluated.
Matthieu. Valette@cern.ch

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THPAF065

Semi-Empirical Hamiltonian Model for Elliptical Cavities

cavity, linac, linear-dynamics, proton

3127

E. Laface, J. F. Esteban Müller
ESS, Lund, Sweden

We propose to use the sum of TM_0m0 modes to treat a radio-frequency superconducting elliptical cavity as a pill-box cavity with variable radius. The amplitudes of the different modes are obtained interpolating the field-map of the cavity with the model. Once the field is calculated, the Hamiltonian of the cavity is constructed and used to evaluate the transfer matrices associated to each step of the field-map. The multi-particle non-linear dynamics can also be evaluated using the Lie Transform of the Hamiltonian. The results are benchmarked against the ESS Linac Simulator contained in the OpenXAL suite.

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THPAF068

Suppression of Instabilities Generated by an Anti-Damper With a Nonlinear Magnetic Element in IOTA

experiment, lattice, optics, damping

3134

E.G. Stern, J.F. Amundson, A. Macridin
Fermilab, Batavia, Illinois, USA

Funding: US Department of Energy
The Integrable Optics Test Accelerator (IOTA) storage ring is being constructed at Fermilab as a testbed for new accelerator concepts. One important series of experiments tests the use of a novel nonlinear magnetic insert to damp coherent instabilities. To test the damping power of the ele- ment, an instability of desired strength may be intentionally excited with an anti-damper. We report on simulations of beam stabilization using the Synergia modeling framework over ranges of driving and damping strengths.

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THPAF069

Particle Tracking Simulation of Collective Modes - Parametric Landau Damping Off Coupling Resonance

damping, coupling, resonance, synchrotron

3137

A. Macridin, J.F. Amundson, A.V. Burov, P. Spentzouris, E.G. Stern
Fermilab, Batavia, Illinois, USA

Employing Synergia simulations with the DMD method we investigate the Landau damping of space charge modes in bunched beams. The simulations reveal two instances of the parametric damping mechanism in bunched beams. The first example occurs in the proximity of coupling resonance and is due to the oscillation of particles' amplitudes in the transverse plane. This oscillation modulates the mode-particle coupling with particle dependent trapping frequency. The second example is due to the modulation of the mode-particle coupling in one transverse plane by the oscillatory motion in the other plane.

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THPAF071

McMillan Lens in a System with Space Charge

emittance, resonance, quadrupole, lattice

3143

I. Lobach
University of Chicago, Chicago, Illinois, USA
S. Nagaitsev, E.G. Stern, T. Zolkin
Fermilab, Batavia, Illinois, USA

Space charge (SC) in a circulating beam in a ring produces both betatron tune shift and betatron tune spread. These effects make some particles move on to a machine resonance and become unstable. Linear elements of beam optics cannot reduce the tune spread induced by SC because of its intrinsic nonlinear nature. We investigate the possibility to mitigate it by a thin McMillan lens providing a nonlinear axially symmetric kick, which is qualitatively opposite to the accumulated kick by SC. Experimentally, the proposed concept can be tested in Fermilab's IOTA ring. A thin McMillan lens can be implemented by a short (70 cm) insertion of an electron beam with specifically chosen density distribution in transverse directions. In this article, to see if McMillan lenses reduce the tune spread induced by SC, we make several simulations with particle tracking code Synergia. We choose such beam and lattice parameters that tune spread is roughly 0.5 and a beam instability due to the half-integer resonance 0.5 is observed. Then, we try to reduce emittance growth by shifting betatron tunes by adjusting quadrupoles and reducing the tune spread by McMillan lenses.

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THPAF075

Numerical Simulations of Space Charge Compensation with an Electron Lens

space-charge, electron, lattice, emittance

3154

E.G. Stern, Y.I. Alexahin, J.F. Amundson, A.V. Burov, A. Macridin, V.D. Shiltsev
Fermilab, Batavia, Illinois, USA

The future high energy physics program at Fermilab requires that the proton complex operate with beam bunch intensities four times larger than is currently handled. At these intensities space charge nonlinear defocussing effects cause unacceptable particle losses especially in the low energy rapid-cycling-synchrotron (RCS) Booster. Focusing electron lens elements may offer a solution by providing partial space charge compensation but there is a need for detailed simulations as this technique has not been demonstrated. We report on high fidelity numerical 6D space charge simulations in a model accelerator lattice with a record high space charge tune shift approaching unity.

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THPAF076

Using Graphic-Turtle with the Particle Beam Optics Laboratory (PBO Lab)

optics, scattering, software, quadrupole

3158

G.H. Gillespie
G.H. Gillespie Associates, Inc., Del Mar, California, USA

A Particle Beam Optics Laboratory (PBO Lab) module has been developed for the Paul Scherrer Institute (PSI) version of the TURTLE program commonly known as Graphic-Turtle. The PSI-TURTLE version extends the original TURTLE program by including several unique beam optics capabilities, as well as by providing a self-contained graphics package. The unique optics modeling, together with the data visualization enhancements, make the PSI-TURTLE program ideal for certain types of beam simulations. The PBO Lab environment provides a single graphic user interface (GUI) that features an easy-to-learn and easy-to-use drag-and-drop beamline construction kit. Underlying the GUI is a sophisticated object model developed specifically for the accelerator community. PBO Lab provides a common interface for multiple charged particle optics codes. Modules have been developed for a number of popular beam optics programs that cover a range of accelerator types and applications. The PSI-TURTLE Module extends those capabilities. The module is described and its main capabilities and limitations are summarized.

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THPAF077

Ion-optical Measurements at CRYRING@ESR during Commissioning

MMI, acceleration, injection, closed-orbit

3161

O. Geithner, Z. Andelkovic, M. Bai, A. Bräuning-Demian, V. Chetvertkova, O. Chorniy, C. Dimopoulou, W. Geithner, O.E. Gorda, F. Herfurth, M. Lestinsky, S.A. Litvinov, S. Reimann, A. Reiter, M. Sapinski, R. Singh, T. Stöhlker, G. Vorobjev, U. Weinrich
GSI, Darmstadt, Germany
A. Källberg
Stockholm University, Stockholm, Sweden

CRYRING@ESR is a heavy ion storage ring, which can cool and decelerate highly charged ions down to a few 100 keV/u. It has been relocated from Sweden to GSI, downstream of the experimental storage ring (ESR), within the FAIR project. The ring will be used as a test facility for FAIR technologies as well as for physics experiments with slow exotic ion beams for several FAIR collaborations: SPARC, BioMat, FLAIR and NUSTAR. CRYRING@ESR is in its commissioning phase since summer 2016. Several ion-optical measurements such as tunes, tune diagram, dispersion, chromaticity and orbit response matrix were performed at the ring. The measurements will be used for several purposes such as improvement of the theoretical model, closed orbit control and correction of unacceptable misalignments, calibration coefficients and field errors.

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THPAF078

Expected Performance of the Stochastic Cooling and RF System in the Collector Ring

bunching, proton, antiproton, emittance

3165

O.E. Gorda, C. Dimopoulou, A. Dolinskyy
GSI, Darmstadt, Germany
T. Katayama
Nihon University, Narashino, Chiba, Japan

The Collector Ring is designed for stochastic cooling of antiprotons or radioactive ions at FAIR. Simulations of the cooling process in combination with the required RF beam manipulations have been done taking into account the improved and recently fixed ion-optics. The measured RF properties of the first of series debuncher system have been considered to evaluate the performance of the bunch rotation, de-bunching and re-bunching process within the planned CR operation cycle. The expected beam parameters and matching at extraction to the HESR storage ring are discussed in this paper. The latest hardware developments of the stochastic cooling system components are also presented.

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THPAF079

Landau Damping and Tune-Spread Requirements for Transverse Beam Stability

octupole, damping, impedance, quadrupole

3168

V. Kornilov, O. Boine-Frankenheim
GSI, Darmstadt, Germany

Passive mitigation methods are effective cures for collective instabilities in ring accelerators. For decades, octupole magnets have been used as an established and well-understood passive mitigation method. Present and the future accelerator facilities, like FAIR or FCC, impose new challenges on the passive mitigation due to higher energies and smaller beam emittances. Lattice resonances usually restrict the tolerable tune-spreads which are essential for the passive mitigation methods. We study the stability of transverse bunch oscillations provided by octupole magnets and radio-frequency quadrupoles. The special focus of our study is on the interplay and role of decoherence, phase-mixing and Landau damping for the different mitigation schemes. Particle tracking simulations are performed and the tune spreads for the different mechanisms are compared with each other and also with analytical dispersion relations.

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THPAF082

Frequency Jump at Low Energies

rfq, linac, emittance, bunching

3176

C. Zhang
GSI, Darmstadt, Germany
H. Podlech
IAP, Frankfurt am Main, Germany

One or more radio-frequency jumps are usually necessary for realizing a ≥100 AMeV/u proton or ion driver linac. Typically, such jumps happen in the range of β = 0.2-0.6 between the resonator structures fitting to this β-range, e.g. DTL, HWR, CCL or elliptical cavities. We propose to perform the first frequency jump already at low energies (β ≤ 0.1) between two RFQ accelerators, which can bring some unique advantages. First studies have been performed and the results proved that this idea is feasible and promising. Many efforts have been and are being made to address the most critical issue for the jumps i.e. the beam matching at the transition.

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THPAF083

LINAC-Multitool - an Open Source Java-Toolkit

linac, cavity, GUI, MMI

3179

M. Schwarz, D. Bade, J. Corbet, H. Podlech
IAP, Frankfurt am Main, Germany

Funding: Work supported by BMBF contr. No. 05P15RFRBA and HIC for FAIR.
Dedicating more precious time to advanced research instead of spending it towards time-consuming routine tasks is a desirable goal in particle accelerator simulation and development. Requirements engineering was started at IAP in order to identify routine processes at our institute's R&D that can be automated or simplified. Results indicated that there were several areas to consider: Bead pull measurements, data processing and visualization for the beam dynamics code LORASR, CST field map processing for the use with TraceWin, conversion between different particle distribution data formats and more. Subsequently development of the LINAC-Multitool started to rationalize these processes and replace preexisting scripts also to ensure consistency of results and increase transparency and reliability of computation. In order to guarantee maintainability, expandability and platform independence, LINAC-Multitool is programmed using Java and will be open source. This contribution presents the current state of development.

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THPAF084

Impact of RF Coupler Kicks on Beam Dynamics in BESSY VSR

cavity, kicker, SRF, lattice

3182

T. Mertens
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), Berlin, Germany
T. Atkinson, F. Glöckner, A. Jankowiak, M. Ries, A.V. Tsakanian
HZB, Berlin, Germany

The expected BESSY II upgrade to BESSY VSR requires the installation of a superconducting RF system, consisting of four cavities. Two cavities will operate at 1.5 GHz and two at 1.75 GHz. Each of them is equipped with a Fundamental Power Coupler and with Higher Order Mode (HOM) damping waveguide couplers. Dedicated simulations of these cavities and couplers have shown that at the location of the FPC the beam will see a transverse kick [*], perturbing the closed orbit and affecting transverse beam dynamics. We present the results of simulations and experiments of the impact on transverse beam dynamics of these coupler induced kicks for different FPC orientations.
[*] Study on RF Coupler Kicks of SRF Cavities in the BESSY VSR Module
A. Tsakanian#, H.-W. Glock, T. Mertens, M. Ries, A. Velez, J. Knobloch
IPAC18

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THPAK001

Impedance Evaluation of In-Vacuum Undulator at KEK Photon Factory

impedance, undulator, factory, vacuum

3200

O. Tanaka, M. Adachi, R. Kato, N. Nakamura, T. Obina, S. Sakanaka, R. Takai, K. Tsuchiya, N. Yamamoto
KEK, Ibaraki, Japan

The estimate of impedance and kick factors of the recently installed at KEK Photon Factory (PF) four In-Vacuum Undulators (IVU) is currently a very important issue, because they could be considerable contributors to the total impedance of PF. Moreover, the coupling impedance of the IVUs could lead to the beam energy loss, changes in the bunch shape, betatron tune shifts and, finally, to the various beam instabilities. Using the simulation tool (CST Particle Studio), longitudinal and transverse impedances of the IVUs were evaluated and compared to analytical formulas and measurement results. The study provides guidelines for mitigation of unwanted impedance, for the accurate estimate of its effects on the beam quality and beam instabilities and also for the impedance budget of a newly designed next-generation machine which has many IVUs and small-aperture beam pipes.

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THPAK005

Measuring the Coupling Impedance of Vacuum Components for the Advanced Photon Source Upgrade Using a Goubau Line

impedance, cavity, vacuum, coupling

3211

M.P. Sangroula
IIT, Chicago, Illinois, USA
R.M. Lill, R.R. Lindberg, R.B. Zabel
ANL, Argonne, Illinois, USA

The Planned upgrade of the Advanced Photon Source to a multi-bend achromat (MBA) will increase the x-ray brightness by two to three orders of magnitude. Storing such an intense beam stably inside the narrow gap vacuum chambers requires sophisticated and appropriately designed rf-components that helps to minimize rf heating and collective instabilities associated with the impedance of these small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. In this paper, we briefly introduce the novel Goubau line (G-line) test fixture for the impedance measurement, at first, and then present our measurements data along with simulations with simulations for various vacuum components designed for the APS Upgrade.

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THPAK008

Space Charge and Microbunching Studies for the Injection Arc of MESA

space-charge, bunching, injection, lattice

3221

A. Khan, O. Boine-Frankenheim
Institut Theorie Elektromagnetischer Felder, TU Darmstadt, Darmstadt, Germany
C.P. Stoll
IKP, Mainz, Germany

For intense electron bunches traversing through bends, as for example the recirculation arcs of an ERL, space charge (SC) may result in beam phase space deterioration. SC modifies the electron transverse dynamics in dispersive regions along the beam line and causes emittance growth for mismatched beams or for specific phase advances. On the other hand, longitudinal space charge together with dispersion can lead to the microbunching instability. The present study focuses on the 180° low energy (5 MeV) injection arc lattice for the multi-turn Mainz Energy-recovering Superconducting Accelerator (MESA), which should deliver a CW beam at 10⁵ MeV for physics experiments with an internal target. We will discuss matching conditions with space charge together with the estimated microbunching gain for the arc. The implication for the ERL operation will be outlined, using 3D envelope and tracking simulations.
Supported by the DFG through GRK 2128

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THPAK009

Benchmark Analyses of Electrostatic Devices for SPIRAL2-DESIR Beam Lines

quadrupole, optics, emittance, electrostatic-devices

3225

L. Perrot, M. Kemel, S. Rousselot
IPN, Orsay, France

Funding: French ANR, Investissements d'Avenir, EQUIPEX. Contract number ANR-11-EQPX-0012.
The new ISOL facility SPIRAL2 is currently being built at GANIL, Caen France. The commissioning of the accelerator is in progress since 2015. SPIRAL2 will produce a large number of new radioactive ion beams (RIB) at high intensities. In 2023, the DESIR facility will receive beams from the upgraded SPIRAL1 facility of GANIL (stable beam and target fragmentation), from the S3 Low Energy Branch (fusion-evaporation and deep-inelastic reactions). In order to deliver the RIB to the experimental set-ups installed in the DESIR hall, 140 meters of beam line are studied since 2014. The transfert lines are today fully design and building will start in 2018. Electrostatic devices (quadrupoles, steerers and deflectors) have been intensively study using various tools. This paper will focus on the detail results of a benchmark using OPERA3D and Comsol Multiphysics apply to the DESIR quadrupole conception.

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THPAK014

Analytical Estimation of the Beam Ion Instability in HEPS

operation, brightness, damping, electron

3231

N. Wang, Z. Duan, S.K. Tian, H.S. Xu
IHEP, Beijing, People's Republic of China

The High Energy Photon Source (HEPS) is a new designed photon source at beam energy of 6 GeV, with natural beam emittance less than 100pm. Due to the small transverse beam size, beam ion instability is one of the potential issues for HEPS. The growth time of the instability is estimated analytically for different operation scenarios. The results show considerably good agreement with the wake strong simulations.

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THPAK015

Impedance and Heat Load Analysis of the Stripline Kicker in HEPS

kicker, impedance, coupling, injection

3234

N. Wang, J. Chen, Z. Duan, H. Shi, S.K. Tian, L. Wang, H.S. Xu
IHEP, Beijing, People's Republic of China

In the High Energy Photon Source (HEPS), strip-line kickers are adopted for beam injection and extraction. Beam coupling impedance contribution from the strip-line kicker is calculated. Detailed studies on the heat load dissipation have been performed. The peak electric field on the blade and the induced voltage on the feedthroughs due to the beam passage are also calculated.

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THPAK018

Recent Developments in DEMIRCI for RFQ Design

rfq, software, multipole, cavity

3243

E. Celebi
IBU, Istanbul, Turkey
O. Cakir, G. Turemen
Ankara University, Faculty of Sciences, Ankara, Turkey
G. Turemen
TAEK, Ankara, Turkey
G. Unel
UCI, Irvine, California, USA

Funding: This project has been supported by TUBITAK with project number 114F10⁶ and 117F143.
DEMIRCI software aims to aid RFQ design efforts by making the process easy, fast and accurate. In this report, DEMIRCI 8-term potential results are compared with the results provided by other commercially available simulation software. Computed electric fields are compared to the re- sults from simulations of a recently produced 352 MHz RFQ. Recent developments like the inclusion of space charge ef- fects in DEMIRCI beam dynamics are also discussed. More- over, further terms are added to 8-term potential to simulate possible vane production errors. The FEM solver was also improved to mesh the cells with errors.

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THPAK021

Design of High Resolution Mass Spectrometer for SPES

dipole, HOM, emittance, high-voltage

3252

M. Comunian, C. Baltador, L. Bellan, M. Cavenago, A. Pisent
INFN/LNL, Legnaro (PD), Italy
E. Khabibullina
ITEP, Moscow, Russia
E. Khabibullina
MEPhI, Moscow, Russia

Within the framework of the SPES (Selective Production of Exotic Species) project at National Institute of Nuclear Physics (INFN laboratory, Legnaro, Italy) the High Resolution Mass Spectrometer (HRMS) will be build. HRMS needs to provide full separation of the ions with mass resolution 1/20000 for the following breeding and acceleration on ALPI Linac. In this article the main design choice of the HRMS and of the transport channel will be reported.

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THPAK022

Beam Dynamic Simulation for the Beam Line from Charge Breeder to ALPI for SPES Project

rfq, linac, experiment, quadrupole

3255

M. Comunian, L. Bellan, A. Pisent
INFN/LNL, Legnaro (PD), Italy
A.V. Ziiatdinova
ITEP, Moscow, Russia
A.V. Ziiatdinova
MEPhI, Moscow, Russia

The SPES project (Selective Production of Exotic Species) is under development at INFN-LNL. This facility is intended for production of neutron-rich Radioactive Ion Beams (RIBs) by ISOL method. The +1 charged beam will be transformed to n+ charge by Charge Breeder (Electron Cyclotron resonance ion source) and reaccelerated by the ALPI (Acceleratore Lineare Per Ioni) superconducting Linac . This paper includes results of beam dynamic simulation at the beam line from Charge Breeder to ALPI.

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THPAK025

Recent Developments in Beam Delivery Simulation - BDSIM

dipole, radiation, sextupole, interface

3266

L.J. Nevay, A. Abramov, S.T. Boogert, H. Garcia Morales, S.M. Gibson, W. Shields, S.D. Walker
JAI, Egham, Surrey, United Kingdom
J. Snuverink
PSI, Villigen PSI, Switzerland

Funding: Work supported by Science and Technology Research council grant 'The John Adams Institute for Accelerator Science' ST/P00203X/1 and Impact Acceleration Account.
Beam Delivery Simulation (BDSIM) is a program to seamlessly simulate the passage of particles in an accelerator, the surrounding environment and detectors. It uses a suite of high energy physics software including Geant4, CLHEP and ROOT to create a 3D model from an optical description of an accelerator and simulate the interaction of particles with matter as well as the production of secondaries. BDSIM is used to simulate energy deposition and charged particle backgrounds in a variety of accelerators worldwide. The latest developments are presented including low-energy tracking extension, more detailed geometry, support for ion beams and improved magnetic fields. A new analysis suite that allows scalable event by event analysis is described for advanced analysis such as the trace back of energy deposition to primary particle impacts.

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THPAK028

Beam Dynamics Simulations in the Dubna SC202 Superconducting Cyclotron for Hadron Therapy

extraction, cyclotron, proton, cavity

3270

O. Karamyshev, G.A. Karamysheva, D.V. Popov, G. Shirkov, S.G. Shirkov
JINR, Dubna, Moscow Region, Russia
V. Malinin
JINR/DLNP, Dubna, Moscow region, Russia

In 2015 the joint project JINR (Dubna, Russia) - ASIPP (Hefei, China) on design and construction of supercon-ducting proton cyclotron SC202 was started. Two cyclo-trons are planned to be manufactured in China, according to the Collaboration Agreement between JINR and ASIPP. The first cyclotron will be used for proton therapy in Hefei and the second one will replace the Phasotron in the research and treatment program on proton therapy in Dubna. New schema of extraction system and results of beam acceleration and extraction simulations for Dubna cyclotron are presented.

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THPAK030

Studies of Longitudinal Dynamics in the Micro-Bunching Instability Using Machine Learning

longitudinal-dynamics, bunching, synchrotron, vacuum

3277

T. Boltz, M. Brosi, E. Bründermann, A.-S. Müller, P. Schönfeldt, M. Yan
KIT, Karlsruhe, Germany
M. Schwarz
CERN, Geneva, Switzerland

The operation of synchrotron light sources with short electron bunches increases the emitted CSR power in the THz frequency range. However, the spatial compression leads to complex longitudinal dynamics, causing the formation of micro-structures in the longitudinal bunch profiles. The fast temporal variation and small scale of these micro-structures put challenging demands on their observation. At the KIT storage ring KARA (KArlsruhe Research Accelerator), diagnostics have been developed allowing direct observation of the dynamics by an electro-optical setup, and indirect observation by measuring the fluctuation of the emitted CSR. In this contribution, we present studies of the micro-structure dynamics on simulated data, obtained using the numerical Vlasov-Fokker-Planck solver Inovesa, and first applications on measured data. To deal with generated data sets in the order of terabytes in size, we apply the machine learning technique k-means to identify the dominant micro-structures in the longitudinal bunch profiles. Following this approach, new insights on the correlation of the CSR power fluctuation to the underlying longitudinal dynamics can be gained.

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THPAK032

Elaborated Modeling of Synchrotron Motion in Vlasov-Fokker-Planck Solvers

synchrotron, electron, storage-ring, damping

3283

P. Schönfeldt, T. Boltz, A. Mochihashi, A.-S. Müller, J.L. Steinmann
KIT, Karlsruhe, Germany

Funding: Funded by the German Federal Ministry of Education and Research (Grant No. 05K16VKA) & Initiative and Networking Fund of the Helmholtz Association (contract number: VH-NG-320).
Solving the Vlasov-Fokker-Planck equation is a well-tested approach to simulate dynamics of electron bunches self-interacting with their own wake-field. Typical implementations model the dynamics of a charge density in a damped harmonic oscillator, with a small perturbation due to collective effects. This description imposes some limits to the applicability: Because after a certain simulation time coherent synchrotron motion will be damped down, effectively only the incoherent motion is described. Furthermore - even though computed - the tune spread is typically masked by the use of a charge density instead of individual particles. As a consequence, some effects are not reproduced. In this contribution, we present methods that allow to consider single-particle motion, coherent synchrotron oscillation, non-linearities of the accelerating voltage, higher orders of the momentum compaction factor, as well as modulations of the accelerating voltage. We also provide exemplary studies - based on the KIT storage ring KARA (KArlsruhe Research Accelerator) - to show the potential of the methods.

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THPAK035

Numerical Tools for Modeling Nonlinear Integrable Optics in IOTA with Intense Space Charge Using the Code IMPACT-Z

space-charge, optics, lattice, proton

3290

C.E. Mitchell, J. Qiang
LBNL, Berkeley, California, USA

Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Integrable Optics Test Accelerator (IOTA) is a novel storage ring under commissioning at Fermi National Accelerator Laboratory designed to investigate the dynamics of beams with large transverse tune spread in the presence of strongly nonlinear integrable optics. Several new numerical tools have been implemented in the code IMPACT-Z to allow for high-fidelity modeling of the IOTA ring during Phase II operation with intense proton beams. A primary goal is to ensure symplectic treatment of both single-particle and collective dynamics. We describe these tools and demonstrate their application to modeling nonlinear integrable dynamics with space charge in IOTA.

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THPAK037

Beam-Loading Transients and Bunch Shape in the Operation of Passive Harmonic Cavities in the ALS-U

cavity, beam-loading, impedance, controls

3298

Z. Pan, S. De Santis, C. Steier, C. Sun, M. Venturini
LBNL, Berkeley, USA
T. Hellert
DESY, Hamburg, Germany
C.-X. Tang
TUB, Beijing, People's Republic of China

The ALS-U is a major upgrade of the LBNL ALS to a diffraction limited light source. The current plan is to replace all the vacuum and magnet components while retaining the existing 500 MHz main and third-harmonic, passively operated, rf cavities, but replacement of the existing rf cavities is also being considered. A new feature, is represented by beam-loading transients associated with a beam consisting of 11 bunch trains separated by 10 ns gaps as needed to enable on-axis swap-out injection. In this paper we study these transients and the associated bunch-to-bunch phase, length, and profile variations.

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THPAK040

Bunched Beam Envelope Instability in a Periodic Focusing Channel

emittance, focusing, lattice, solenoid

3301

J. Qiang
LBNL, Berkeley, California, USA

The space-charge driven envelope instability presents a great danger in high intensity accelerator design. In this paper, we report on the study of bunched beam envelope instability in a periodic focusing channel using three-dimensional envelope model for a 3D uniform Waterbag distribution and a 3D Gaussian distribution. Our results show that the envelope instability stopband becomes broader with the increase of longitudinal focusing and are not sensitive to the type of distribution. Self-consistent macroparticle simulations using both distributions show similar structure in emittance growth but also extra instability stopbands. The emittance growth from the Waterbag distribution has larger stopband than that from the Gaussian distribution.

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THPAK042

On Long-Term Space-Charge Tracking Simulation

space-charge, emittance, lattice, optics

3305

J. Qiang
LBNL, Berkeley, California, USA

The nonlinear space-charge effects in high intensity accelerator can degrade beam quality and cause particle losses. Self-consistent macroparticle tracking simulations have been widely used to study these space-charge effects. However, it is computationally challenging for long-term tracking simulation of these effects. In this paper, we study a fully symplectic self-consistent particle-in-cell model and numerical methods to mitigate numerical emittance growth. We also discuss about a fast alternative frozen space-charge model that has a potential to improve computational speed significantly.

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THPAK043

Performance Optimization of a Beam Dynamics PIC Code On Hybrid Computer Architectures

GPU, kicker, plasma, HOM

3309

Zh.C. Liu
IHEP, Beijing, People's Republic of China
J. Qiang
LBNL, Berkeley, California, USA

The self-consistent multi-particle tracking based on particle-in-cell method (PIC) has been widely used in particle accelerator beam dynamics study. However, the PIC simulation is time-consuming and needs to use modern parallel computers for high resolution applications. In this paper, we implemented and optimized a parallel beam dynamics PIC code on two types of hybrid parallel computer architectures: one is the GPU and GPU cluster, while the other is the "Knight Landing" CPU cluster.

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THPAK044

Self-Consistent Modeling using a Lienard-Wiechert Particle-Mesh Method

space-charge, radiation, synchrotron, emittance

3313

R.D. Ryne, C.E. Mitchell, J. Qiang
LBNL, Berkeley, California, USA
B.E. Carlsten
LANL, Los Alamos, New Mexico, USA

In this paper we describe a parallel, large-scale simulation capability using a Lienard-Wiechert Particle-Mesh (LWPM) method. The approach is a natural extension of the convolution-based technique to solve the Poisson equation in space-charge codes. It provides a unified method to compute both Coulomb-like self-fields and radiative phenomena like coherent synchrotron radiation (CSR). The approach brings together several mathematical and computational capabilities including the use of integrated Green function (IGF) methods and adaptive quadrature methods. We will describe the theoretical model and our progress to date.

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THPAK046

The Ion-Hose Instability in High-Current Multi-Pulse Induction Linacs

electron, induction, vacuum, experiment

3320

C. Ekdahl
LANL, Los Alamos, New Mexico, USA

The ion-hose instability has long been considered a danger for long-pulse, high-current electron linear induction accelerators (LIAs)*. This instability is enabled by beam-electron ionization of residual background gas in the accelerator. The space-charge of the high-energy beam ejects low-energy electrons from the ionized channel, leaving a positively-charged ion channel that attracts the electron beam. The beam can oscillate in the potential well around the channel position. Likewise, the electron beam attracts the ions, which can oscillate about the beam position. Because of the vast differences in particle mass, the oscillations are out of phase, and the amplitudes grow unstably. The number of instability e-foldings is proportional to the channel ion density*, which in turn is proportional to the background pressure and pulse length. This scaling of the instability growth was demonstrated on the long-pulse DARHT-II linear induction accelerator (LIA) at Los Alamos**. The ion-hose instability is also problematic for high-current multi-pulse LIAs, because ion recombination times are so very long at typical background pressures. Moreover, because of low ion channel ion densities, and massive ions, channel expansion is too slow to reduce the instability growth by very much. In particular, the ion channel is expected to persist and its density to increase during the 3-microsecond duration of a four-pulse burst from the 2-kA, 20-MeV Scorpius LIA now being developed. Recent simulations with an experimentally validated code that was used to predict DARHT-II growth rates have shown that the magnetic focusing field designed for Scorpius will be strong enough to inhibit ion-hose instability if the background pressure is kept below a value that is readily attainable with the present designs of induction cells and other accelerator components. Details and results of these calculations are the subject of this presentation.
*H. L. Buchanan, Phys. Fluids, vol. 30, pp. 221 - 231, 1987
**C. A. Ekdahl, et al., IEEE Trans. Plasma Sci., vol. 34, pp. 460-466, 2006

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THPAK047

Comparison of Profile Measurements and TRANSPORT Beam Envelope Predictions Along the 80-m LANSCE pRad Beamline

linac, emittance, proton, diagnostics

3323

P.K. Roy, C. Pillai, C.E. Taylor
LANL, Los Alamos, New Mexico, USA

Funding: *Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
The Proton Radiography (pRad) experimental facility beam transport line is over 80 meters in length starting from the end of the LANSCE linear accelerator. The 800-MeV beam is transported through a beam line containing many bending and focusing elements before it reaches the pRad beam optics system where the beam spot size requirement is nominally 2 mm (RMS). Here we discuss the efforts to reconcile the beam transport inconsistencies (sizes) seen between comparisons of the beam sizes obtained using the LANL version of the beam envelope code TRANSPORT with those measured along the beam line. The transverse input beam parameters for the code were extracted from a fit to several wire-scanner measurements located in the downstream portion of the LINAC. The longitudinal input beam parameters were extrapolated from lower-energy information. Recently, new measurements were made of the beam line element locations and compared with legacy drawings. Beam envelope measurements made at various locations throughout the beam line using wire scanners and gated imaging systems were compared to the calculated results. The predicted beam envelopes and measured data agree within expected errors.
*Los Alamos National Laboratory (LA-UR-17-30876)

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THPAK049

Simulation Code Design for the Interpreted Language Using the Compiled Module

interface, EPICS, linac, lattice

3327

K. Fukushima, M.A. Davidsaver, Z.Q. He, M. Ikegami, G. Shen, T. Yoshimoto, T. Zhang
FRIB, East Lansing, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DESC0000661.
We are planning to use two types of the accelerator simulation codes for FRIB (Facility for Rare Isotope Beams). One is the linear envelope tracking code "FLAME" for fast simulations. FLAME can calculate the FRIB-linac beam envelope within an order of ms. This is useful in systematic surveys, wide range optimizations and so forth. This code, written in C++, was designed with Python interface from the beginning. On the other hand, "Advanced-IMPACT" is the particle tracking code dedicated for precise and realistic calculations, which can simulate the particle losses, nonlinear and space-charge effects. This code is refactored from the Fortran code IMPACT-Z developed in LBNL. Both codes provide the compiled modules for Python to support flexible inputs and direct outputs management in memory. In other words, they can be directly connected to the modern scientific tools through the Python interface without delay in the data transport. In addition, these modules can accomplish the interactive simulation processes without losing computational efficiency. We report the knowledges applicable for other accelerator simulation codes among those obtained through these developments and designs.

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THPAK050

MuSim, a User-Friendly Interface for Multiple Simulation Codes

interface, proton, real-time, controls

3330

T.J. Roberts
Muons, Inc, Illinois, USA

MuSim is a new and innovative graphical framework that permits the user to construct, explore, optimize, analyze, and evaluate nuclear, accelerator, and other particle-based systems efficiently and effectively. It is designed for both students and experienced scientists to use in dealing with the many modeling tools and their different description languages and data formats. Graphical interfaces are used throughout, making it easy to construct the system graphically, display the system with particle tracks, analyze results, and use on-screen controls to vary parameters and observe their effects in (near) real time. Such exploration is essential to give users insight into how systems behave, and is valuable to both new users and experienced system designers. The use of URL-based component libraries will encourage collabor-ation among geographically diverse teams. This project will facilitate access to advanced modeling and simulation tools for inexperienced users and provide workflow management for them and advanced users.

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THPAK051

Computer Simulation of Explosive Emission Electrons Acceleration and X-ray Quantum Generation in Pulse Coaxial Diode System with Interior Anode

cathode, electron, radiation, target

3333

V.I. Rashchikov, A.A. Isaev, A.E. Shikanov, E.A. Shikanov
MEPhI, Moscow, Russia

Computer simulation of electrons from explosive emission acceleration and X-ray quantum generation in pulse coaxial diode system with interior anode, which is used in accelerating tube of compact X-ray generator* with Tesla transformer as high voltage source, was done. The results obtained allow us to choose accelerating tube diode system geometry for different running modes. Comparison of numerical results with experimental data of dose rate dependence on the distance from vacuum tube anode and energy at first circuit Tesla transformer was fulfilled.
*Patent RF N71817, 03.10.2007

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THPAK052

Single Bunch Instabilities in FCC-ee

impedance, collider, electron, vacuum

3336

E. Belli
Sapienza University of Rome, Rome, Italy
G. Castorina, M. Migliorati
INFN-Roma1, Rome, Italy
G. Rumolo
CERN, Geneva, Switzerland
B. Spataro, M. Zobov
INFN/LNF, Frascati (Roma), Italy

FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes.

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THPAK061

Magnetized and Flat Beam Generation at the Fermilab's FAST Facility

quadrupole, emittance, cathode, solenoid

3364

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.J. Crawford, D.R. Edstrom, D. Mihalcea, S. Nagaitsev, P. Piot, A.L. Romanov, J. Ruan, V.D. Shiltsev
Fermilab, Batavia, Illinois, USA

Funding: This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.
Canonical angular momentum (CAM) dominated beams can be formed in photoinjectors by applying an axial magnetic field on the photocathode surface. Such a beam possess asymmetric eigenemittances and is characterized by the measure of its magnetization. CAM removal using a set skew-quadrupole magnets maps the beam eigenemittances to the conventional emittance along each transverse degree of freedom thereby yielding flat beam with asymmetric transverse emittance. In this paper we report on the experimental generation of CAM dominated beam and their subsequent transformation into flat beams at the Fermilab Accelerator Science and Technology (FAST) facility. Our results are compared with numerical simulations and possible applications of the produced beams are discussed.

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THPAK062

Bunch Compression of Flat Beams

emittance, experiment, cavity, booster

3368

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.J. Crawford, D.R. Edstrom, D. Mihalcea, S. Nagaitsev, P. Piot, A.L. Romanov, J. Ruan, V.D. Shiltsev
Fermilab, Batavia, Illinois, USA

Funding: This work is supported by the DOE contract No.DEAC02-07CH11359 to the Fermi Research Alliance LLC. A.H. is supported by the DOE under contract No. DE-SC0011831 with Northern Illinois University.
Flat beams can be produced via a linear manipulation of canonical angular momentum (CAM) dominated beams using a set of skew-quadrupole magnets. Recently such beams were produced at Fermilab Accelerator Science and Technology (FAST) facility. In this paper, we report the results of flat beam compression study in a magnetic chicane at an energy of E~32 MeV. Additionally, we investigate the effect of energy chirp in the round-to-flat beam transform. The experimental results are compared with numerical simulations.

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THPAK064

Theoretical Modeling of Electromagnetic Field from Electron Bunches in Periodic Wire Medium

radiation, electron, lattice, FEL

3376

S.S. Chuchurka, A.I. Benediktovitch
BSU, Minsk, Belarus, Belarus
S.N. Galyamin, V.V. Vorobev
Saint Petersburg State University, Saint Petersburg, Russia
A. Halavanau
Northern Illinois University, DeKalb, Illinois, USA

Funding: Work supported by the Grant from Russian Foundation for Basic Research (No. 17-52-04107).
The interaction of relativistic electrons with periodic structures results in radiation by a number of mechanisms. In case of crystals one obtains parametric X-ray radiation, its frequency is determined by distance between crystallographic planes and direction of electron beam. If instead of crystal one considers a periodic structure of metallic wires with period of the order of mm, one can expect emission of THz radiation. In the present contribution we consider theoretical approaches for modeling of the distribution of electromagnetic field from electron bunches in lattice formed by metallic wires. The analytical description is possible for the case of wires with small radius, the range of validity is checked by numerical simulations. The intensity of radiation will be significantly increased if the electrons in the bunch could radiate coherently. Two possibilities will be discussed: the prebunching of the beam and the self-modulation of the beam due to interaction with radiated field.

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THPAK065

Application of Transverse-to-Longitudinal Phase-Space-Exchanged Beam Produced from a Nano-Structure Photocathode to a Soft X-Ray Free-Electron Laser

cathode, acceleration, quadrupole, laser

3379

A. Lueangaramwong, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
G. Andonian
RadiaBeam, Santa Monica, California, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Nano-structured cathodes can form transversely modulated beams which can be subsequently converted to temporally modulated beam via a transverse-to-longitudinal phase space-exchanging beamline. We demonstrate via numerical simulation the generation of transversely modulated beam at the nm scale and investigate the corresponding enhancement in a soft-X-ray SASE free-electron laser. Our study is supported by start-to-end simulation combining WARP, IMPACT-T and GENESIS(FEL process) and focuses on the optimization of the beamline to preserve initial modulation at the nanometer level. We also discuss the scaling of the concept to shorter-wavelengths.

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THPAK067

Progress Toward a Self-Consistent Beam at the Spallation Neutron Source

injection, solenoid, kicker, quadrupole

3382

J.A. Holmes, S.M. Cousineau, T.V. Gorlov, M.A. Plum
ORNL, Oak Ridge, Tennessee, USA
N.J. Evans
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the US DOE. This research was supported by the DOE Office of Science, Accelerator and Detector Research Program.
We have proposed to inject a self-consistent "rotating" beam into the Spallation Neutron Source (SNS). Self-consistent beam distributions are defined to be ellipsoidal, or elliptical in 2D, distributions that have uniform density and that retain these properties under all linear transformations. We have made much progress since the original proposal. We have demonstrated computationally the feasibility of injecting a rotating beam under realistic physics assumptions. We have optimized the injection scheme with respect to beam loss and to minimum necessary hardware changes. We have also determined how existing SNS beam diagnostic equipment can be used to verify the self-consistency of the injected beam. This paper will report the details of this work as well as the status of plans to carry out the self-consistency experiments.

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THPAK071

Simulation Study of the Magnetized Electron Beam

solenoid, cathode, electron, gun

3395

S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
ODU, Norfolk, Virginia, USA
J. F. Benesch, F.E. Hannon, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman
JLab, Newport News, Virginia, USA

Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177
Electron cooling of the ion beam plays an important role in electron ion colliders to obtain the required high luminosity. This cooling efficiency can be enhanced by using a magnetized electron beam, where the cooling process occurs inside a solenoid field. This paper compares the predictions of ASTRA and GPT simulations to measurements made using a DC high voltage photogun producing magnetized electron beam, related to beam size and rotation angles as a function of the photogun magnetizing solenoid and other parameters.

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THPAK072

Generation of Flat Ultra-Low Emittance Beams

quadrupole, emittance, cathode, permanent-magnet

3398

N.R. Bell
UCLA, Los Angeles, USA
L. Phillips
PBPL, Los Angeles, USA

By placing a cathode in a longitudinal magnetic field generated by a solenoid or permanent magnet, angular-momentum dominated electron beams can be produced. Such beams can be uncoupled using a skew-quadrupole channel to remove the angular momentum and yield flat beams with an ultralow emittance in one of the transverse dimensions. Flat beams have immediate relevance in our pursuit of ultrahigh brightness in two dimensions for dielectric laser accelerator (DLA) or slab beam applications. We are currently investigating the possibility of implementing flat beam generation at the UCLA Pegasus beamline. We utilize particle tracking simulations to optimize the transverse emittance ratio and normalized transverse emittance. Our simulations show emittance ratios of more than 100 and normalized emittances in the <5 nm range in the vertical dimension, matching analytic estimates. In addition to simulation results, experimental plans to implement and test the flat beam transform (FBT) are also discussed.

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THPAK075

Simulation of Particle Interactions in a High Intensity Radio-Frequency Quadrupole for Molecular Hydrogen Ions

rfq, proton, electron, acceleration

3405

M.J. Easton, H.P. Li, Y.R. Lu, Z. Wang
PKU, Beijing, People's Republic of China
J. Qiang
LBNL, Berkeley, California, USA

High-intensity deuteron accelerators run the risk of deuteron-deuteron interactions leading to activation. For this reason, in the commissioning phase, a molecular hydrogen ion (H²⁺) beam is often used as a model for the deuteron beam without the radiation risk. However, composite ions are susceptible to particle interactions that do not affect single ions, such as stripping of electrons and charge exchange. Such interactions affect the beam dynamics results, and may lead to production of secondary particles, which in high-intensity beams may cause damage to the accelerator and reduce the quality of the beam. In order to understand these effects, we have modified the IMPACT-T particle tracking code to include particle interactions during the tracking simulation through a high-intensity continuous-wave (CW) radio-frequency quadrupole (RFQ). This code is also designed to be easily extensible to other interactions, such as collisions or break-up of heavier ions. Preliminary results and possibilities for future development will be discussed.

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THPAK076

Development and Benchmarking of the IMPACT-T Code

rfq, linac, SRF, space-charge

3408

H.P. Li, M.J. Easton, Y.R. Lu, Z. Wang
PKU, Beijing, People's Republic of China
J. Qiang
LBNL, Berkeley, California, USA

The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code.

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THPAK078

GPT-CSR: a New Simulation Code for CSR Effects

radiation, emittance, electromagnetic-fields, linac

3414

S.B. van der Geer, M.J. de Loos
Pulsar Physics, Eindhoven, The Netherlands
A.D. Brynes, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
I.D. Setija, P.W. Smorenburg
ASML Netherlands B.V., Veldhoven, The Netherlands

For future applications of high-brightness electron beams, including the design of next generation FEL's, correct simulation of Coherent Synchrotron Radiation (CSR) is essential as it potentially degrades beam quality to unacceptable levels. However, the long interaction lengths compared to the bunch length, numerical cancellation, and difficult 3D retardation conditions make accurate simulation of CSR effects notoriously difficult. To ease the computational burden, CSR codes often make severe simplifications such as an ultra-relativistic bunch travelling on a prescribed reference trajectory. Here we report on a new CSR model implemented in the General Particle Tracer (GPT) code that avoids most of the usual assumptions: It directly evaluates the Liénard'Wiechert potentials based on the stored history of the beam. It makes no assumptions about reference trajectories, and also takes into account the transverse size of the beam. Example results demonstrating normalised emittance growth in the first bunch compressor of FERMI@Elettra are presented.

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THPAK079

New Algorithms in Zgoubi

dipole, proton, polarization, factory

3418

D.T. Abell
RadiaSoft LLC, Boulder, Colorado, USA
F. Méot
BNL, Upton, Long Island, New York, USA

Funding: This work was supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0017181.
The particle tracking code Zgoubi*,** is used for a broad array of accelerator design studies, including FFAGs*** and EICs****,*****. In this paper, we describe recent work aimed at improving Zgoubi's speed and flexibility. In particular, we describe a new implementation of the Zgoubi tracking algorithm that requires significantly less memory and arithmetic. And we describe a new algorithm that performs symplectic tracking through field maps. In addition, we describe the current efforts to parallelize Zgoubi.
*https://sourceforge.net/projects/zgoubi/
**F. Méot, FERMILAB-TM-2010, 1997
***F. Lemuet et al., NIM-A, 547:638, 2005
****F. Méot et al., eRHIC/45, 2015
*****F. Lin et al., IPAC17, WEPIK114, 2017

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THPAK082

Simulation of Perturbative Effects in IOTA

lattice, optics, octupole, emittance

3422

C.C. Hall, D.L. Bruhwiler, N.M. Cook, J.P. Edelen, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA

The Integrable Optics Test Accelerator (IOTA) is being commissioned at Fermi National Laboratory for study of the concept of nonlinear integrable optics. The use of a special nonlinear magnetic element introduces large tune spread with amplitude while constraining the idealized dynamics by two integrals of motion. The nonlinear element should provide suppression of instabilities through nonlinear decoherence. We examine the case of a bunch injected off-axis and the resulting damping of centroid oscillations from decoherence. A simple model of the damping is described and compared to simulation.

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THPAK083

An s-Based Symplectic Spectral Space Charge Algorithm

space-charge, optics, plasma, proton

3425

N.M. Cook, D.T. Abell, D.L. Bruhwiler, J.P. Edelen, C.C. Hall, S.D. Webb
RadiaSoft LLC, Boulder, Colorado, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC001340.
Traditional finite-difference particle-in-cell methods for modeling self-consistent space charge introduce non-Hamiltonian effects that make long-term tracking in storage rings unreliable. Foremost of these is so-called grid heating. Particularly for studies where the Hamiltonian invariants are critical for understanding the beam dynamics, such as nonlinear integrable optics, these spurious effects make interpreting simulation results difficult. To remedy this, we present a symplectic spectral space charge algorithm that is free of non-Hamiltonian numerical effects and, therefore, suitable for long-term tracking studies. We present initial results demonstrating the implementation of the algorithm, using a spectral representation of the fields and macro particles to preserve Hamiltonian structures. We then discuss applications to the Integrable Optics Test Accelerator (IOTA), currently under construction at Fermilab.

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THPAK085

3D Space Charge in Bmad

space-charge, software, lattice, brightness

3428

C.E. Mayes
SLAC, Menlo Park, California, USA
R.D. Ryne
LBNL, Berkeley, California, USA
D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

We present a parallel fast Fourier transform based 3D space charge software library based on integrated Green functions. The library is open-source, and has been structured to easily be used by existing beam dynamics codes. We demonstrate this by incorporating it with the Bmad toolkit for charged particle simulation, and compare with analytical formulas and well-established space charge codes.

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THPAK087

Software-Computing System for Numerical Modelling of Beam Dynamics in Accelerators

software, experiment, controls, interface

3435

E. Krushinevskii, E. Sboeva
Saint Petersburg State University, Saint Petersburg, Russia
S.N. Andrianov, A.N. Ivanov, N.V. Kulabukhova
St. Petersburg State University, St. Petersburg, Russia

The spectrum of software packages for the physics of charged particles beams is extremely wide. From most popular and effective systems can be allocated such programs as COSY Infinity, MAD X, MARYLIE, TRANSPORT. Heterogeneous individual formats of input and output data, the lack of a common and user-friendly interface and the narrow specialization of these programs poses a number of challenges for the modern researchers. It significantly reduces the effectiveness and quality of corresponding computational experiments. In this article we present a universal tool for automation and acceleration of computing experiments. The authors consider a method for developing the concept and prototype of a corresponding software package that would combine the advantages of existing (non-commercial) systems. This software will be able to unify the input and output data format for certain programs, visualize the information in various ways, provide reference and training information for "beginners". The results obtained within the developed framework will be a significant contribution both to the development of numerical and symbolical methods for solving evolution nonlinear equations.

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THPAK088

Matrix Representation of Lie Transform in TensorFlow

network, storage-ring, GPU, linear-dynamics

3438

A.N. Ivanov, S.N. Andrianov, N.V. Kulabukhova, A.A. Sholokhova
St. Petersburg State University, St. Petersburg, Russia
E. Krushinevskii, E. Sboeva
Saint Petersburg State University, Saint Petersburg, Russia

In the article, we propose an implementation of the matrix representation of Lie transform using TensorFlow as a computational engine. TensorFlow allows easy description of deep neural networks and provides automatic code execution on both single CPU/GPU and cluster architectures. In this research, we demonstrate the connection of the matrix Lie transform with polynomial neural networks. The architecture of the neural network is described and realized in code. In terms of beam dynamics, the proposed technique provides a tool for both simulation and analysis of experimental results using modern machine learning techniques. As a simulation technique one operates with a nonlinear map up to the necessary order of nonlinearity. On the other hand, one can utilize TensorFlow engine to run map optimization and system identification problems.

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THPAK091

Design of the New Proton Synchrotron Booster Absorber Scraper (PSBAS) in the Framework of the Large Hadron Collider Injection Upgrade (LIU) Project

impedance, vacuum, proton, booster

3444

L. Teofili, M. Migliorati
Sapienza University of Rome, Rome, Italy
J.A. Briz Monago, M. Calviani, N. Chritin, J.J. Esala, S.S. Gilardoni, I. Lamas Garcia, J. Maestre, T. Polzin, T.L. Rijoff
CERN, Geneva, Switzerland
T.L. Rijoff
TU Darmstadt, Darmstadt, Germany

The Large Hadron Collider (LHC) Injector Upgrade (LIU)Project at CERN calls for increasing beam intensity for the LHC accelerator chain. Some machine components will not survive the new beam characteristics and need to be rebuilt for the new challenging scenario. This is particularly true for beam intercepting devices (BIDs) such as dumps, collimators, and absorber/scrapers, which are directly exposed to beam impacts. In this context, this work summarizes conceptual design studies on the new Proton Synchrotron Booster (PSB) Absorber/Scraper (PSBAS), a device aimed at cleaning the beam halo at the very early stage of the PSB acceleration. This paper outlines the steps performed to fulfil the component design requirements. It discusses thermo-mechanical effects as a consequence of the beam-matter collisions, simulated with the FLUKA Monte Carlo code and ANSYS finite element software; and the impedance minimization study performed to prevent beam instabilities and to reduce RF-heating on the device.

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THPAK092

Analysis on the Mechanical Effects Induced by Beam Impedance Heating on the HL-LHC Target Dump Injection Segmented (TDIS) Absorber

impedance, injection, HOM, shielding

3448

L. Teofili, M. Migliorati
Sapienza University of Rome, Rome, Italy
M. Calviani, D. Carbajo Perez, S.S. Gilardoni, F. Giordano, I. Lamas Garcia, G. Mazzacano, A. Perillo-Marcone
CERN, Geneva, Switzerland

The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity. In such a scenario, critical accelerator devices need to be redesigned and rebuilt. Impedance is among the design drivers, since its thermo-mechanical effects could lead to premature device failures. In this context, the current work reports the results of a multiphysics study to assess the electromagnetic and thermo-mechanical behaviour of the Target Dump Injection Segmented (TDIS). It first discusses the outcomes of the impedance analysis performed to characterise the resistive wall and the high order resonant modes (HOMs) trapped in the TDIS structures. Then, their RF-heating effects and the related temperature distribution are considered. Finally, mechanical stresses induced by thermal gradients are studied in order to give a final validation on the design quality.

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THPAK093

A Multi-Physics Approach to Simulate the RF Heating 3D Power Map Induced by the Proton Beam in a Beam Intercepting Device

impedance, HOM, injection, proton

3452

L. Teofili, M. Migliorati
Sapienza University of Rome, Rome, Italy
D. Carbajo Perez, F. Giordano, I. Lamas Garcia, G. Mazzacano
CERN, Geneva, Switzerland

The project High Luminosity Large Hadron Collider (HL- LHC) calls for a streaking beam intensity and brightness in the LHC machine. In such a scenario, beam-environment electromagnetic interactions are a crucial topic: they could lead to uneven power deposition in machine equipment. The resulting irregular temperature distribution would gener- ates local thermal gradients, this would create mechanical stresses which could lead to cracks and premature failure of accelerator devices. This work presents a method to study this phenomenon by means of coupled electro-thermo- mechanical simulations. Further, examples of applications on real HL-LHC devices is also discussed.

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THPAK100

Design and Fabrication of a Combined Function Magnet Prototype for Siam Photon Source

quadrupole, dipole, multipole, synchrotron

3466

P. Sunwong, B. Boonwanna, S. Chaichuay, P. Klysubun, A. Kwankasem, C.P. Preecha, V. Sooksrimuang
SLRI, Nakhon Ratchasima, Thailand

A prototype of combined function magnet has been developed for a new facility of Siam Photon Source (SPS). The magnet is a combined dipole and quadrupole with the required dipole field and quadrupole gradient of 0.6 T and 30 T/m, respectively. The high field gradient is attained from an offset quadrupole design pioneered by the European Synchrotron Radiation Facility (ESRF). The prototype magnet is fabricated and tested in-house. Magnetic field quality is characterized by the field homogeneity in the central field region and multipole components of the magnetic field. Calculated results show that the gradient deviation and the normalized multipole error are less than 0.01 within the good field region of ±8 mm. Preliminary measurements show a good agreement with the calculation, although further measurements are required to verify the results and the multipole error of magnetic field.

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THPAK103

Pragmatic Method of Deducing a Wake Function for a General 3D Structure

impedance, wakefield, vacuum, resonance

3469

G. Skripka
CERN, Geneva, Switzerland
R. Nagaoka
SOLEIL, Gif-sur-Yvette, France

A key quantity in simulating collective beam instabilities is the wake potential of a bunch of particles whose charge distribution is continuously evolving in time. However, obtaining such wake potential is only possible if a wake excited by a single particle in the surrounding environment is known. A practical self-consistent approach was developed to obtain an effective wake function from a numerical wake potential computed for a finite length bunch. The wake potential is processed to a numerical impedance which is decomposed into a set of well-known analytical wake functions. The decomposed impedance is then transformed back into time domain and, thus, converted into an effective wake function which is by nature physical and most consistent with the numerical wake potential. Though the method is limited by the initial numerical impedance data and the choice of impedance decomposition, the retrieved wake function can be used in instability simulations with a bunch whose length is comparable to that used in the electromagnetic field solver. We show that the method can be applied to a general 3D structure, which allows finding effective wake functions of realistic vacuum chambers.

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THPAK109

Improved Simulation for Centre Region of TRIUMF 500 MeV Cyclotron with Space Charge

space-charge, TRIUMF, focusing, cyclotron

3489

Y.-N. Rao, R.A. Baartman, T. Planche
TRIUMF, Vancouver, Canada

Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada
The TRIUMF 500 MeV cyclotron delivered routinely a total current up to 200 μA protons for 15 years till 2001. Since 2002, developments towards 300 μA total extraction became compelling because of the ISAC expansion. To meet future requirements (for addition of a new beam-line), a total extraction of 310 − 450 μA shall be envisioned. With such an increase of beam current, the space charge effect becomes a major concern in the centre region, as it limits the maximum amount of beam current achievable out of the machine. Therefore, numerical simulation on beam orbits with the space charge force has has been initiated, starting from the injection gap. This study is focused on the beam bunches which are very long compared with transverse size (because TRIUMF extraction is by stripping of H-minus and separated turns are not required). In order to achieve an improved understanding of the space charge effect, we worked to validate the simulations performed without and with the space charge force, using realistic centre region geometry. Our goal is to work out the space charge limits and their dependence upon the bunchers, rf voltage, and matching. In this paper we present our recent progress in this study.

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THPAK110

Correction of ν_r-ν_z=1 Resonance in TRIUMF Cyclotron

resonance, coupling, cyclotron, TRIUMF

3492

Y.-N. Rao, R.A. Baartman, T. Planche
TRIUMF, Vancouver, Canada

Funding: TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada
The second order linear coupling resonance nu_r-nu_z=1 is driven by an asymmetry in the median plane of the cyclotron due to presence of the first harmonic in B_r component. In TRIUMF cyclotron, this resonance is encountered at about 166 MeV and 291 MeV, where nu_r=1.2 and nu_z=0.2. When the beam is off-centered radially to pass through this resonance, the radial oscillation gets converted into vertical oscillation, which can cause beam loss to occur, though these loss modes do not reduce the machine transmission under normal operation. In this paper, we present the results of simulations and measurements that we have performed to correct this resonance by using the existing harmonic coils.

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THPAK111

Envelope Calculations on the Ion Beam Injection and Extraction of CANREB EBIS

electron, injection, extraction, TRIUMF

3496

M.H. Pereira-Wilson
UW/Physics, Waterloo, Ontario, Canada
R.A. Baartman, S. Saminathan
TRIUMF, Vancouver, Canada

An electron beam ion source (EBIS) is being developed as a charge state breeder for the production of highly charged ions in the CANREB (CANadian Rare isotope facility with Electron Beam ion source) project at TRIUMF. The multiple tunable electrodes of the EBIS, coupled with the necessity of directing both an electron beam and an ion beam of varying charge, impose a challenging task for the optimization of the beam optics. With this in mind, beam envelope simulations have been performed to determine the acceptance of the EBIS and the emittance of the extracted ion beam. The electric field of the different EBIS electrodes were modelled using finite element analysis software and the envelope simulations were executed using beam envelope code TRANSOPTR. Preliminary results show envelope calculation as a viable candidate for tuning the injection and extraction optics of the EBIS.

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THPAK112

Toward an End-to-End Model for ISAC-I Accelerators

ISAC, rfq, linac, TRIUMF

3500

O. Shelbaya, O.K. Kester
TRIUMF, Vancouver, Canada

Diurnal-like transmission variations in the ISAC-I warm accelerator system necessitates periodic retuning by operators. While beam loss points are well known, re-tuning nevertheless results in additional downtime and reduced count rates at experiments. This has motivated the development of an end-to-end simulation of the ISAC-I linear accelerator (linac) system to understand and characterize the nature of transmission instabilities spanning several hours to days.

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THPAK116

Modeling Surface Roughness Effects and Emission Properties of Bulk and Layered Metallic Photocathode

electron, emittance, experiment, cathode

3515

D.A. Dimitrov, G.I. Bell
Tech-X, Boulder, Colorado, USA
I. Ben-Zvi, J. Smedley
BNL, Upton, Long Island, New York, USA
J. Feng, S.S. Karkare, H.A. Padmore
LBNL, Berkeley, California, USA

Funding: This work was supported by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under Contract Nos. DE-SC0013190, DE-AC02-05CH11231, and KC0407-ALSJNT-I0013.
The thermal limit of the intrinsic emittance of photocathodes represents an important property to measure experimentally and to understand theoretically. Detailed measurements of intrinsic emittance have become possible in momentatron experiments. Moreover, recent developments in material design have allowed growing photoemissive layers with controlled surface roughness. Although analytical formulations of the effects of roughness have been developed, a full theoretical model and experimental verification are lacking. We aim to bridge this gap by developing realistic models for different materials in the three-dimensional VSim particle-in-cell code. We have recently implemented modeling of electron photo-excitation, transport, and emission from photoemissive layers grown on a substrate. We report results from simulations with these models on electron emission from antimony and gold. We consider effects due to density of states, photoemissive layer thickness, surface roughness and how they affect the spectral response of quantum yield and intrinsic emittance.

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THPAK117

Space Charge Limitations for Bunch Compression in Synchrotrons

space-charge, resonance, emittance, synchrotron

3518

Y.S. Yuan, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
G. Franchetti, I. Hofmann
GSI, Darmstadt, Germany

Bunch compression achieved via a fast bunch rotation in longitudinal phase space is a well-accepted scheme to generate short, intense ion bunches for various applications. During bunch compression, coherent beam instabilities and incoherent single particle resonances can occur because of increasing space charge, resulting in an important limitation for the bunch intensity. We present an analysis of the relevant space charge driven beam instability and resonance phenomena during bunch compression. A coupled longitudinal-transverse envelope approach is compared with Particle-In-Cell (PIC) simulations. Two distinct cases of crossing are discussed and applied to the GSI SIS18 heavy-ion synchrotron. It is shown that during bunch compression, the 90^° condition of phase advance is associated with a fourth order single particle resonance and the 120^° condition with the recently discovered dispersion-induced instability. The agreement between the envelope and PIC results indicates that the stop band is defined by the 120^° dispersion instability, which should be avoided during bunch compression.

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THPAK127

Toroidal Merger Simulations for the JLEIC Bunched Beam Electron Cooler Ring

electron, emittance, solenoid, space-charge

3540

A.V. Sy
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The bunched beam electron cooler ring for the Jefferson Lab Electron-Ion Collider (JLEIC) requires a merger system to transport magnetized electron beams of two different energies to the same energy recovery linac (ERL) beamline. The system is especially challenging compared to existing mergers for ERL or hadron cooling applications (as at COSY) due to the small separation in energy between the two beams; for the JLEIC bunched beam cooler, the two beam energies may only differ by a factor of 4. An additional complication is the use of a magnetized beam. A toroidal merger system is studied using G4Beamline/GEANT4. Preservation of the quality of the low energy beam from the injector is especially vital for efficient cooling performance and compatibility with the ERL. Effects of the toroidal system on transverse and longitudinal emittances of the magnetized beams, as well as space charge effects, are presented and discussed.

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THPAK137

Beam-Based Sextupolar Nonlinearity Mapping in CESR

sextupole, experiment, resonance, lattice

3565

L. Gupta, Y.K. Kim
University of Chicago, Chicago, Illinois, USA
S. Baturin
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
M.P. Ehrlichman, J.M. Maxson, R.E. Meller, D. L. Rubin, D. Sagan, J.P. Shanks
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams
In order to maintain beam quality during transport through a storage ring, sextupole magnets are used to make chromatic corrections, but necessarily introduce deleterious effects such as nonlinear resonances and reduced dynamic aperture. Implementing intricate sextupole distributions to mitigate these effects will rely on precision beam-based measurement of the applied sextupole distribution. In this work, we generalize previous sextupole mapping techniques by using resonant phase-locked excitation of the beam at the Cornell Electron Storage Ring (CESR), which accounts for variations in the normal mode tunes on a turn by turn basis. The methods presented here are applied to simulation and actual turn by turn data in CESR for both simplified and realistic sextupole distributions.

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THPAK138

Development of Efficient Tree-Based Computation Methods for the Simulation of Beam Dynamics in Sparsely Populated Phase Spaces

electron, FEL, bunching, HOM

3569

Ph. Amstutz
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
M. Vogt
DESY, Hamburg, Germany

Collective instabilities pose a major threat to the quality of the high brightness electron beams needed for the operation of a free electron laser. Multi-stage bunch compression schemes have been identified as a possible source of such an instability. The dispersive sections in these compressors translate energy inhomogeneities within the bunch into longitudinal charge density inhomogeneities. In conjunction with a collective force driving locally density-dependent energy modulations this leads to intricate longitudinal beam dynamics. As a consequence of the thin shape those bunches form in the longitudinal phase space, efficient simulation of such systems is not straight forward. At high resolutions, the numerical representation of the phase space density on a uniform grid is too wasteful, due to the large unpopulated phase space regions. In this contribution we present advances made in the development of a simulation code that addresses the problem of sparsely populated phase spaces by means of quadtree domain decomposition. A focus lies on the explanation of the underlying tree data structure.

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THPAK140

Pyroelectric Detection of Coherent Radiation on the CLARA Phase 1 Beamline

radiation, electron, dipole, detector

3577

B.S. Kyle
University of Manchester, Manchester, United Kingdom
R.B. Appleby, T.H. Pacey
UMAN, Manchester, United Kingdom
P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
J. Wolfenden
The University of Liverpool, Liverpool, United Kingdom

The impacts of coherent synchrotron radiation (CSR) and space charge in the bunch compressor section of the CLARA Free Electron Laser (FEL) are expected to be significant, given the relatively high charge and short bunch lengths expected. The General Particle Tracer (GPT) code allows for the modelling of these effects in tandem, presenting an opportunity to more reliably estimate their effects on the CLARA beam. To provide confidence in future studies using GPT, a benchmarking study on the CLARA Phase 1 beamline is presented alongside relevant simulations. This study will make use of pyroelectric detectors to measure the emitted coherent power of the CLARA beam as it passes through a dispersive section whilst varying the chirp imparted on the bunches longitudinal phase space (LPS). Simulations presented demonstrate the viability of such a study, with energies between ∼ 10-100 nJ per pulse expected to be incident upon the detector face.

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THPAK141

Initial Tests of Nonlinear Quasi-Integrable Optics at the University of Maryland Electron Ring

octupole, electron, optics, experiment

3581

H. Baumgartner, B.L. Beaudoin, I. Haber, T.W. Koeth, D.B. Matthew, K.J. Ruisard
UMD, College Park, Maryland, USA

Funding: Funding for this project and travel is provided by DOE-HEP, NSF GRFP and NSF Accelerator Science Program.
An octupole channel has been inserted into the University of Maryland Electron Ring (UMER), in order to investigate the mitigation of destructive resonances as a novel approach in high-intensity beam transport. The individual octupole magnets have been characterized using our in-house 3-dimensional magnet mapping stage, with a measured gradient of 51.6 ± 1.5 T/m3/A. A single section (20°) of an 18-cell FODO lattice has been replaced by a longitudinally-varying octupole channel constructed from seven flexible printed circuits (PCBs). We present the design of the channel and preliminary beam based measurements on the ring.

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THPAL004

Research and Development of RF System for SC200 Cyclotron

cavity, LLRF, cyclotron, acceleration

3616

G. Chen, C. Chao, G. Liu, X.Y. Long, Z. Peng, Y. Song, Y.S. Wang, C.S. Wei, M. Xu, Q. Yang, X. Zhang, Y. Zhao
ASIPP, Hefei, People's Republic of China
L. Calabretta, A.C. Caruso
INFN/LNS, Catania, Italy
O. Karamyshev, G.A. Karamysheva, N.A. Morozov, E. Samsonov, G. Shirkov
JINR, Dubna, Moscow Region, Russia

A 200MeV compact isochronous superconducting cyclotron, named SC200, for proton therapy is under development by collaboration of ASIPP (Hefei, China) and JINR (Dubna, Russia). The radio frequency (RF) system as one of most significant subsystems in cyclotron consists of acceleration cavity, low level RF, RF source and transmission network. SC200 has two cavities connected in the centre, which are operated at 91.5 MHz with second harmonic. To meet the required acceleration voltage, the cavities have been carefully designed with comprised choices between several aspects, such as Q factor, mechanic stability and so on. The low-level RF (LLRF) system has been implemented by using the FPGA to achieve the significant accelerating voltage with an amplitude stability of <0.2% and a phase stability of < 0.1 degree. The cavity and LLRF system have been tested outside of cyclotron, the results will be presented. For future, the commissioning of whole RF system will be started after the assembly of SC200 at the end of 2019.

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THPAL017

From design to alignment of ThomX quadrupoles

quadrupole, multipole, HOM, alignment

3660

C. Vallerand, R. Marie, H. Monard
LAL, Orsay, France
J. Campmany, J. Marcos, V. Massana
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
J. Chavanne, G. Le Bec
ESRF, Grenoble, France
M.-E. Couprie, A. Lestrade, A. Loulergue, F. Marteau, M. Ros
SOLEIL, Gif-sur-Yvette, France

Quadrupoles for Thomx Facility have been carefully designed and measured due to high constraints of the storage ring. The need of a compact accelerator, 70 m2 on floor, as well as a beam life time of 20 ms, led to the following requirements for the quadrupole : a gradient of 5 T/m with 20.5 mm radius bore, harmonic content better than few 1.10^-3 at the reference radius of 18 mm, no cross-talk with sextupole placed within 5 cm and a precision of the magnetic axis of 100 μm and the roll angle of 300 μrad for measurements and alignment. Total of 41 quadrupoles have been built and all measured by a rotating coil at ALBA and SOLEIL, providing multipole components, transfer function and magnetic center. Cross-check measurements have also been carried out with a versatile stretched wire from ESRF at LAL. This paper mainly describes results of simulations with OPERA and RADIA and provides the results of measurements with these three benches. These results will be compared and highlighted important points for the alignment and installation of quadrupoles in an accelerator.

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THPAL018

DQW HOM Coupler Design for the HL-LHC

HOM, impedance, cavity, GUI

3663

J.A. Mitchell
Lancaster University, Lancaster, United Kingdom
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga
CERN, Geneva, Switzerland
S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA

HOMs in the DQW crab cavity can produce large heat loads and beam instabilities as a result of the high current HL-LHC beams. The DQW crab cavity has on-cavity, coaxial HOM couplers to damp the HOMs whilst providing a stop-band response to the fundamental mode. Manufacturing experience and further simulations give rise to a set of desirable coupler improvements. This paper will assess the performance of the current HOM coupler design, present operational improvements and propose an evolved design for HL-LHC.

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THPAL020

Design of Asymmetric Quadrupole Gradient Bending R&D Magnet for the Advanced Light Source Upgrade (ALS-U)

dipole, quadrupole, multipole, lattice

3667

J.-Y. Jung, M. Leitner, N. Li, E.R. San Mateo, C. Steier, C.A. Swenson, M. Venturini
LBNL, Berkeley, California, USA

Lawrence Bekerley National Laboratory (LBNL) is en-gaged in the development of magnets for the upgrade of the ALS synchrotron (ALS-U) [1]. The proposed ALS-U lattice is a 9-bend achromat reproducing the existing 12-fold symmetric ALS foot print. The ALS-U lattice requires strong focusing elements and the dipole magnet requires high gradient larger than 46 T/m. This paper presents the detailed design of the R&D dipoles under construction.

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THPAL023

Assessing the Continued Suitability of an Existing Water System for an Accelerator Upgrade

operation, neutron, interface, HOM

3673

W.C. Barkley, C.E. Buechler, E.N. Pulliam
LANL, Los Alamos, New Mexico, USA

This paper assesses the continued suitability of an existing Water Cooling System (WCS) for cooling intermediate and high-power RF power amplifiers at the Los Alamos Neutron Science Center (LANSCE). At LANSCE, the high-power and intermediate power amplifiers installed in the 70s were at end-of-life with obsolete parts and no suitable replacements available to extend their life. The LANSCE Refurbishment Project was initiated (now complete) to replace these amplifiers and to utilize already existing WCSs. Two existing WCSs were repurposed and one new WCS was designed and installed. Unscheduled, intermittent water system trips on one of the WCSs has prompted the engineering group to drill down into the original decision, build a flow model and assess some of the legacy components' suitability to solve the problem. This paper discusses the general approach, troubleshooting and solution recommendations to be made for resolution of the intermittent issues.

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THPAL024

A Simple Variable Focus Lens for Field Emitter Cathodes

cathode, emittance, focusing, laser

3677

R.L. Fleming, H.L. Andrews, K. Bishofberger, D. Kim, J.W. Lewellen, K.E. Nichols, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

Funding: Los Alamos National Laboratory LDRD Program
We present the design for a simple, variable-focus solenoidal lens with integrated emittance filtering. The design was developed as a first-iteration injection optics solution for transport of a beam from a field-emitter cathode into a dielectric laser accelerator structure. The design is easy to fabricate and, while based on permanent magnets, can readily be modified to allow for remote control of the focal length. The emittance is controlled via selection of collimating irises. The focal length can be changed by altering the spacing between two permanent ring magnets. Results from fabrication and initial testing will be presented.

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THPAL033

Measurement of the Internal Dark Current in a High Gradient Accelerator Structure at 17 GHz

multipactoring, acceleration, electron, experiment

3705

H. Xu, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA

Funding: Work supported by the U.S. Department of Energy, Office of High Energy Physics, under Grant No. DE-SC0015566
We report a study of internal dark current generation by multipactor inside a 17 GHz single cell standing wave disk-loaded waveguide accelerator structure. The multipactor takes place on the side wall of the central cell, driven by the local rf electric and magnetic fields. Theory indicates that a resonant multipactor mode with two rf cycles can be excited near 45 MV/m gradient and a single rf cycle multipactor mode near 60 MV/m. The accelerator structure had two thin slits opened on the side wall of the central cell to directly extract and measure the internal dark current. The dark current was measured as a function of the gradient up to a gradient of 70 MV/m. The experimental results agreed well with theory, showing the two predicted multipactor modes. To further study the effect of the central cell side wall surface properties on the structure performance, we prepared and tested a second structure with the central cell side wall coated with a layer of diamond-like carbon. The comparison of the results showed that the coating reduced the internal dark current and thus enhanced the structure performance considerably.

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THPAL041

Power Coupler Design for the LUCRECE Project

cavity, SRF, coupling, linac

3732

H. Guler, D. Auguste, J. Bonis, O. Bouras, M. El Khaldi, W. Kaabi, P. Lepercq
LAL, Orsay, France

The LUCRECE project aims at developing an elementary RF system (cavity, power source, LLRF and controls) suitable for continuous (CW) operation at 1.3 GHz. This effort is made in the framework of the advanced and compact FEL project LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation), using superconducting linac technology for high repetition rate and multi-user operation (www.lunex5.com). In this context, based on its large experience on coupler design and RF conditioning, LAL Laboratory is in charge of the design and the fabrication of RF couplers that could operate at up to 15-20 kW in CW mode. For this purpose, geometry based on CORNELL 65kW CW couplers will me modified to fulfil the LCLS2 type cavity with the high necessary coupling level. Electromagnetic simulations and optimisation and associated thermal heating will be discussed. Methods to decrease the thermal impact, and strategy for RF conditioning will be considered.

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THPAL043

Dipole Magnets for the Technological Electron Accelerators

dipole, electron, permanent-magnet, radiation

3739

I.S. Guk, O.M. Bovda, V.O. Bovda, A.N. Dovbnya, S.G. Kononenko, V.N. Ljashchenko, A. Mytsykov, L.V. Onishchenko, A.Y. Zelinsky
NSC/KIPT, Kharkov, Ukraine

Permanent magnets made of rare earth elements alloys allow to develop compact dipole magnets for the applied electron accelerator. These devices can be used for the beam trajectory bending as well as for the beam characteristics measurements. For NSC KIPT linear accelerator «EPOS» a dipole magnet on the base of Nd-Fe-B alloy has been designed and developed. The magnet provides 90 degrees bend of 23 MeV electron beam. The design value of magnetic field at the beam design trajectory is 0.5 Т. The magnet effective length is 242 mm. The magnet temperature can be changed with thermos-stabilization system. For NSC KIPT 10 MeV LU-10 applied accelerator a dipole magnet of Sm2Co17 alloy has been manufactured. The maximum magnet field of the magnet is 0.3 Т. The magnet layout allows easy magnet assembling at the accelerator chamber. The magnet is used for the beam energy measurement and accelerator beam energy turning. After energy turning the magnet should be removed from the accelerator lattice.

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THPAL045

Determination of the Electron Bunch Length With Third Harmonic Cavity for the Taiwan Photon Source

cavity, operation, SRF, electron

3745

Z.K. Liu, F.Y. Chang, L.-H. Chang, M.H. Chang, S.W. Chang, L.J. Chen, F.-T. Chung, M.-C. Lin, C.H. Lo, Ch. Wang, M.-S. Yeh, T.-C. Yu
NSRRC, Hsinchu, Taiwan

The Taiwan Photon Source (TPS) is a modern 3 GeV low emittance light source with RMS bunch lengths of about 3 mm at a beam current of 500 mA and operating gap voltage of 3.2 MV. With a higher harmonic cavity, we could increase the Touschek lifetime and lower the heat load of in-vacuum undulators by lengthening the bunch lengths. Preliminary studies show that for full and uni-form fill patterns, the bunch lengths could be increased by a factor of four. However, this calculation ignores phase transient effects and may overestimate the effect of harmonic cavities. A multi-bunch, multi-particle tracking method has been developed to determine the bunch lengths for non-uniform fill patterns, which also takes phase transient effects into account and the expected maximum bunch lengthening factor for different TPS operation conditions are discussed.

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THPAL049

Power Supply Decoupling Design

controls, power-supply, coupling, electron

3751

Y.T. Li, F.Y. Chang
NSRRC, Hsinchu, Taiwan

After an actual operation of the phase-shifted magnet's power supply was conducted, it was found that the currents in the two modules of magnets would be coupled each other. In order to solve this mutual coupling current, a decoupling controller is designed. From the experiment results indicate that it does not only solve the issue of coupling current but also shorten the rising time of the power supply current. This helps to increase the power supply bandwidth.

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THPAL052

Finite Element Analysis on Beam-Induced Heat Load in in-Vacuum Undulators with a Small Magnet Gap

undulator, synchrotron, vacuum, synchrotron-radiation

3760

J.-C. Chang, Y.-H. Liu
NSRRC, Hsinchu, Taiwan

In-vacuum undulators with a small gap and short period have been applied in synchrotron accelerators for hard X-rays users for years. However, beam-induced heat load resulted from synchrotron radiation or the image current will not only degrade the performance of undulator but damage the magnet foil. It is difficult to quantitatively study heat transfer phenomenon of the magnet foil through physical experiment. In this study, finite element analysis was applied to study the effect of beam-induced heat load on an in-vacuum undulator.

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THPAL055

A Novel High Step-down DC-DC Converter with Isolated Transformer and Switched Capacitor Techniques for Corrector Magnet Bulk Power in Taiwan Photon Source

ISOL, power-supply, high-voltage, operation

3769

Y.S. Wong, K.-B. Liu
NSRRC, Hsinchu, Taiwan
J.F. Chen
NCKU, Tainan city, Taiwan

In this study, a high step down DC-DC converter was successfully integrated using switch capacitor and isolated transformer techniques. Switching capacitor techniques has use of capacitor parallel energy storage and series release of the way to improve the voltage conversion ratio. In addition, the output voltage ripple will be smaller due to the input current being continuous, the inductance is an element to prevent a surge current. The isolated transformer techniques has use of inductor coil turns ratio to achieve high conversion ratio. But, the leakage inductor and parasitic capacitance on the power switch will be resonant to generate a surge voltage spike when the power switch S is turned off. So that, additional a passive clamp circuit, energy of leakage inductor will be recycled to clamp capacitor and voltage stress of main power switch. The power switch S can be selected a lower Rds(on) components and reduce the conduction losses to improve power converter efficiency. Step down mode operation principle and steady-state analysis were discussed in this paper. Finally, simulation and prototype circuit is implemented in this laboratory to verify the performance, the step-down DC-DC converter is input voltage 400-V, output voltage 48-V and output power 960-W.

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THPAL059

TEMPERATURE ISSUES OF THE TPS BPMS

impedance, wakefield, site, resonance

3781

Y.T. Huang, C.-C. Chang, C.M. Cheng, P.J. Chou, Y.C. Yang
NSRRC, Hsinchu, Taiwan

Since the TPS is capable to operate at higher currents, long-term 400mA conditioning runs were conducted. Current-dependent temperature data of BPMs were collected and analysed for both, aluminium and stainless steel BPM chambers. To better understand beam coupling effects in different types of TPS BPMs, electromagnetic and thermal simulation models were established. In this paper, we discuss associated results of such studies.

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THPAL060

Advanced Modeling of Klystrons by the Tesla-Family of Large-Signal Codes

klystron, cavity, impedance, experiment

3785

I.A. Chernyavskiy, D.K. Abe, B. Levush, A.N. Vlasov
NRL, Washington, DC, USA
T.M. Antonsen
UMD, College Park, Maryland, USA
T.M. Antonsen
Leidos Corp, Billerica, MA, USA
J. Rodgers
Naval Research Laboratory (NRL), Washington, USA

Funding: US Office of the Naval Research
Klystrons and IOTs are widely used or proposed to be used in accelerators as high-power RF sources. Development and optimization of klystron and IOT designs is aided by the use of different simulation tools, including highly efficient large-signal codes. We present an overview of the advances in the code development and modeling using Naval Research Laboratory (NRL) set of TESLA-family of large-signal codes, suitable for the modeling of single-beam and multiple beam klystrons and IOTs. Original 2D large-signal algorithm of the code TESLA* was developed for the modeling of klystrons based on (relatively) high Q resonators and is applicable to the multiple-beam devices in an approximation of identical beams/beam-tunnels. Parallel extension of TESLA algorithm (code TESLA-MB**) enabled an accurate, quasi-3D modeling of multiple-beam devices with non-identical beams/beam-tunnels. Recently developed more general TESLA-Z algorithm*** is based on the impedance matrix approach and enabled geometry-driven large-signal modeling. Examples of applications of TESLA-family of codes to the modeling of advanced single-beam and multiple-beam klystrons (and IOTs) will be presented.
*A.N. Vlasov, et al,IEEE TPS, v.30(3), 1277-1291, June 2002
**I.A. Chernyavskiy, et al.,IEEE TPS, v.36(3), 670-681, June 2008
***I.A. Chernyavskiy, et al.,IEEE TED, v.64(2), 536-542, Feb 2017

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THPAL061

Simulation of Pulsed Temperature Rise in Cryogenic Copper RF Cavity Achieving a Very High Accelerating Field

cavity, accelerating-gradient, coupling, cryogenics

3788

T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Sumitomo
LEBRA, Funabashi, Japan

A cryogenic C-band photocathode RF electron gun cavity has been studied at Nihon University LEBRA in cooperation with KEK. The RF properties of a cold model measured at 20 K have shown good agreement with those expected from computer simulations using the cavity surface resistance predicted by the theory of the anomalous skin effect. Recent studies on the vacuum RF breakdown at high electric fields suggest that the temperature in the cavity surface during the high power RF pulse has a significant effect on the behavior of the breakdown rate. In order to investigate the breakdown property of the cryogenic cavity aiming at a very high accelerating field with as low breakdown rate as possible, one-dimensional simulations of the temperature rise in the cavity surface have been done for various combinations of the RF pulse width and the peak input RF power. The evaluation will be taken into consideration in the design of a new high power cryogenic cavity that has basically the same configuration with the cold model.

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THPAL063

RF and Thermo-Mechanical Considerations in Designing the Waveguide Iris Coupler for the Drift Tube Linac in the ORNL Spallation Neutron Source

cavity, GUI, DTL, vacuum

3796

S.W. Lee, Y.W. Kang
ORNL, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT Battelle, LLC, under contract DE AC05 00OR22725 for the U.S.DOE
The Spallation Neutron Source (SNS) employs tapered ridge waveguide iris couplers to power six drift tube linac (DTL) cavity structures with pulsed RF systems using 2.5MW klystrons at 402.5MHz. All DTL iris couplers have been operating continuously for more than a decade without replacement. Transferring high RF energy to the cavities requires robust RF and mechanical performances with respect to power dissipation, electrical breakdown, and vacuum pressure. Considering the upcoming full 1.4MW operation and the future proton power upgrade (PPU) project, the structural design and the material selection needed to be reviewed for potential spare manufacturing. The existing design and the modified design with improvements to the coupler have been numerically studied. For the study, 3D models were used for RF and structural characterizations of the waveguide iris couplers on the DTL cavity. RF and thermo-mechanical co-simulations were performed to assess the effects of using the different materials and the structural modification.

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THPAL067

Room Temperature Measurements of Higher Order Modes for the SPS Prototype RF-Dipole Crabbing Cavity

HOM, cavity, dipole, luminosity

3805

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
P. Berrutti
Fermilab, Batavia, Illinois, USA
N.A. Huque, H. Park
JLab, Newport News, Virginia, USA

LHC High Luminosity Upgrade will be developing two local crabbing systems to increase the luminosity of the colliding bunches at the ATLAS and CMS experiments. One of the crabbing systems uses the rf-dipole cavity design that will be crabbing the beam in the horizontal plane. The fully integrated crabbing cavity has two higher order mode couplers in damping those excited modes. Currently two sets of HOM couplers have been fabricated at Jefferson Lab for prototyping and testing with the LARP crabbing cavities. This paper presents the measurements of the higher order modes with the prototype HOM couplers carried out at room temperature.

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THPAL069

Simulation of a 10 mm Diameter Cascaded Plasma Window

plasma, cathode, vacuum, experiment

3812

P.P. Gan, S. Huang, Y.R. Lu, S.Z. Wang, K. Zhu
PKU, Beijing, People's Republic of China

As a windowless vacuum device, the 10 mm diameter 60 mm long plasma window designed by Peking University only achieved to separate 28.8 kPa from 360 Pa experimentally with 50 A direct current and 2.5 kW power. Based on our 10 mm diameter plasma window, we have proposed a cascaded plasma window to achieve the isolation of atmosphere and high vacuum. In this paper, a numerical 2D FLUENT-based magneto-hydrodynamic simulation on 10 mm diameter cascaded plasma window was developed. The gas inlet, arc creation and plasma expansion segments are all contained in this model. A set of parameters including pressure, temperature, velocity and current distribution were obtained and analysed. In our first simulation, the isolation of 100 kPa and 50 Pa pressure has been realised, and some interesting phenomena occurred.

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THPAL070

Multi-Physics Analysis of Two Bunchers for CIFNEF

cavity, beam-transport, target, neutron

3815

Q.Y. Tan, M.J. Easton, Q. Fu, P.P. Gan, H.P. Li, Y.R. Lu, Z. Wang
PKU, Beijing, People's Republic of China

CIFNEF(Compact Intense Fast NEutron Facility) project will accelerate and deliver a 5 MeV deuteron beam to the targets to produce high-intense neutrons. A 2.5 MHz pulsed deuteron beam with bunch width within 2 ns is needed on the targets at last. To fulfill the special requirements of the beam dynamics, two types of bunchers are adopted in the CIFNEF. One is a 10.156 MHz buncher used in the low energy beam transport (LEBT) line to longitudinally focus the 50 keV deuteron beam to the RFQ longitudinal acceptance with 4 kV effective voltage. A lumped element model is adopted because of the low frequency and it consists of an inductance coil in parallel with the capacitance of drift tube. The other one is an 81.25 MHz buncher used in the high energy beam transport (HEBT) line to longitudinally focus the 5 MeV deuteron beam to 2 ns. A QWR cavity with 2-gaps is used to provide 150 kV effective voltage. Thermal and structural analyses have been carried out on these two bunchers. Details of simulations of these two bunchers are presented and discussed in this paper.

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THPAL078

In-Vacuum Lambertson Septum for SPEAR3 Low Emittance Injection

septum, vacuum, storage-ring, injection

3831

M.A.G. Johansson, J. Langton, J.A. Safranek
SLAC, Menlo Park, California, USA
S.C. Gottschalk
STI Magnetics LLC, Woodinville, USA

Funding: Work supported by DOE Contract No. DE-AC02-76SF00515
A new in-vacuum Lambertson septum magnet is being designed for the SPEAR3 storage ring, intended to replace the existing septum to allow injection into a new lower emittance operation mode for SPEAR3. The new septum design is constrained to fit in the same length and have the same bend angle as the existing injection septum, so as to minimize changes to surrounding storage ring and transfer line components, while also meeting stringent requirements on the stored beam leakage field. This has led to a design using Vanadium Permendur alloy for the septum pole pieces, with shaping of the inner profile of the stored beam channel to minimize the leakage fields indicated in 2D and 3D magnetic simulations.

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THPAL080

Parallel-Feed SRF Accelerator Structures

cavity, SRF, coupling, impedance

3835

P.B. Welander, Z. Li, M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory, under contract DE-AC02-76SF00515.
Development of SRF accelerator technology that enables both higher gradient and higher efficiency is crucial for future machines. While much of the recent R&D focus has been on materials and surface science, our aim is to optimize the cavity geometry to maximize performance with current materials. The recent demonstration of a highly efficient parallel-feed NCRF structure at SLAC has served as a proof-of-concept. Applied to SRF, such a structure could dramatically reduce power consumption while boosting the achievable gradient. Instead of coupled elliptical cells, our structure employs isolated reentrant cells. To feed RF power to the cavities, each cell is directly coupled to an integrated manifold. The structure is made in two parts, split along the beam axis, which are then joined. Such a structure has been fabricated from bulk Cu and tested at SLAC - designed for X-band, it operates at a record gradient of 150 MV/m. Adapting to SRF at 1.3 GHz and fabricating from Nb, such a cavity could achieve more than 50% lower RF loss and 40% higher gradient compared to the TESLA cavity. We will describe our simulations and propose an experimental roadmap for demonstrating this technology.

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THPAL084

An X-Band Lineariser for the CLARA FEL

cavity, FEL, wakefield, klystron

3848

L.S. Cowie, A.D. Brynes, J.K. Jones, A.E. Wheelhouse, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R. Apsimon, G. Burt, W.L. Millar
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
Ö. Mete
UMAN, Manchester, United Kingdom
A.J. Moss
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

The CLARA FEL at Daresbury Laboratory will employ four S-band linacs to accelerate electron bunches to 250 MeV/c. In order to compress the bunch sufficiently to achieve peak currents suitable for FEL lasing, one must compensate for curvature imprinted on the longitudinal phase space of the bunch. For CLARA a harmonic RF linearization system has been designed to achieve this requirement. The linearization will be achieved by an X-band travelling wave cavity of the PSI/CERN design, which incorporates wake-field monitoring of the bunch position. A five-axis mover will align the cavity to the beam axis. Pulse compression of a 6 MW klystron pulse will provide the required power to achieve a 30 MV/m operational gradient.

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THPAL092

Test Particle Monte Carlo Simulation of NEG Coated Narrow Tubular Samples

vacuum, ECR, experiment, SRF

3862

O. Seify, A.N. Hannah, O.B. Malyshev, Sirvinskaite, R. Sirvinskaite, R. Valizadeh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
Sirvinskaite, R. Sirvinskaite
Loughborough University, Loughborough, Leicestershire, United Kingdom

The pumping properties of the NEG coated vacuum chambers play an important role in the efficiency of vac-uum system of accelerators. The sticking probability of the NEG films is one the most important parameters to characterise the pumping properties of the NEG coated vacuum chambers. In order to investigate the NEG film sticking probability, Test Particle Monte-Carlo (TPMC) models were used. The models were based on the design of the installed experimental setup in ASTeC Vacuum Science group laboratory at Daresbury Laboratory (DL). The results of the simulations have been used for inter-preting the results of the measurements in the experi-mental setup.

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THPAL105

Lower Critical Field Measurement System of Thin Film Superconductor

controls, experiment, SRF, embedded

3882

H. Ito
Sokendai, Ibaraki, Japan
C.Z. Antoine
CEA/IRFU, Gif-sur-Yvette, France
A. Four
CEA/DRF/IRFU, Gif-sur-Yvette, France
H. Hayano, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
R. Ito, T. Nagata
ULVAC, Inc, Chiba, Japan
Y. Iwashita, R. Katayama, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
H. Oikawa
Utsunomiya University, Utsunomiya, Japan

Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
Superconducting thin film is the promising technology to increase the performance of SRF cavities. The lower critical field Hc1, which is one of the important physical parameters characterizing a superconducting material, will be enhanced by coating Nb with thin film superconductor such as NbN. To investigate the performance of thin film, we developed the Hc1 measurement system using the third harmonic response of applied AC magnetic field. The measurement system consists of helium cryostat with two of GM refrigerators, sample Cu stage, solenoid coil Cu mount, solenoid coil, temperature sensors, and liquid helium level meter. AC magnetic field is produced by a coil which is driven by function generator and power amplifier at around 1 kHz. In order to control the temperature of the sample stage and coil mount, the depth of thermal anchors attached to the stage and the mount can be moved by the motor. By this temperature control the sample state can be easily transferred from Meissner state to mixed state. So that the measurement is repeated for various applied magnetic field, and the transition curve can be made. In this report, performance of the measurement system is described.

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THPAL108

In-Situ Characterization of Normal Conducting RF Cavities in Solaris Light Source Storage Ring

cavity, HOM, storage-ring, ISOL

3891

P.B. Borowiec, A.I. Wawrzyniak
Solaris National Synchrotron Radiation Centre, Jagiellonian University, Kraków, Poland
J. Björklund Svensson
Lund University, Division of Atomic Physics, Lund, Sweden

The SOLARIS 1.5 GeV storage ring is equipped with two 100 MHz active cavities and two 3rd harmonic passive cavities. They are in operation since 2015. For control of their respective working points, knowledge about cavity voltage and higher order mode (HOM) frequency spec-trum is mandatory. After their installation in the storage ring and connection of the RF feeder to a high power isolator and a transmitter, the influence of the external elements on the quality factor and the HOM spectrum should be verified with respect to simulations of a simpli-fied model of a stand-alone cavity. This paper will pre-sent results of in-situ cavity measurements to qualify the HOM placement and their quality factor. HOM meas-urements have been performed in the range 100 MHz to 1.3 GHz for active cavities and 300 MHz to 1.5 GHz for 3rd harmonic cavities at three different temperatures under ultra-high vacuum conditions for each cavity separately. The measurement and analysis methodology will also be presented

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THPAL109

The New 118 MHz Cavity for RF Development Activities of the RF for Accelerator Laboratory at SLRI

cavity, HOM, coupling, impedance

3895

N. Juntong, K. Kittimanapun, P. Sunwong
SLRI, Nakhon Ratchasima, Thailand
A. Sutchada
Walailak University, Nakhon Si Thammarat, Thailand

The RF for accelerator laboratory is established at SLRI to perform RF related development activities of the current light source and the future synchrotron light facility in Thailand. One of activities is to build an in-house RF cavity. It will be used for testing of RF amplifier unit and the developed LLRF system. The cavity is a nose-cone pill-box cavity operating at 118 MHz and aiming at 100 kV gap voltage. Details of designing in particular the inner surface profile, the RF properties, the higher order modes properties, the RF power coupler, and the tuning mechanism will be presented with the manufacturing timeline.

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THPAL112

RF Matching Circuit for CANREB RFQ

rfq, TRIUMF, network, pick-up

3902

T. Au, B. Barquest, J.J. Keir, V. Zvyagintsev
TRIUMF, Vancouver, Canada

A RF matching circuit has been developed to provide two phase RF voltage of 1.2 kVpp at 3 MHz and 6 MHz for the CANREB RFQ structure with an equivalent capacitive load of 300 pF. The RF matching circuit utilizes pi-network with two phase transformer. Beyond RF drive the CANREB structure requires pulse DC bias with amplitude up to 500 V. Results of development and testing of RF matching circuit and filters are presented in this paper.

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THPAL113

The Design of 1 MeV Proton LINAC Operating in CW

cavity, linac, proton, resonance

3905

N.V. Avreline
TRIUMF, Vancouver, Canada

Experimental results and computer simulations of electrodynamic and thermodynamic characteristics are presented for an accelerating structure that is excited in the TM010 mode and that has the accelerating channel of URAN-1M located in the diametric plane. The idea of using this structure in the particle accelerator URAN-1M, located at the Baikov Institute of Metallurgy and Materials Science, with the goal of increasing the average beam current is explored.

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THPAL114

The Analytical Model of the Helical Accelerating Structure of Linac with Helix Outside of the Vacuum Chamber

vacuum, experiment, resonance, TRIUMF

3908

N.V. Avreline
TRIUMF, Vancouver, Canada

An analytical model of the helical RF resonator for the single charged 250 keV nitrogen ion implanter operating in CW was developed. The analytical model allowed to determine the geometry of the accelerating structure and to construct CST Microwave Studio and ANSYS HFSS models based on this analytical model. Results obtained from the analytical model and simulations were within 5% of each other. The experimental investigation of the accelerating section confirmed that the models are correct. The accelerating section was tuned and verified for the right accelerating field distribution and operating frequency. Finally, the section was successfully tested in 2 kW CW RF power.

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THPAL115

The Design of 1.1 MW RF Dummy Load for the RF System of 520 MeV Cyclotron

cyclotron, TRIUMF, pick-up, controls

3911

N.V. Avreline, Y. Bylinskii, B. Jakovljevic, Y. Ma, V. Zvyagintsev
TRIUMF, Vancouver, Canada

The RF System of 520-MeV Cyclotron is operating at 23 MHz with 1 MW CW RF power. The RF dummy load is required to troubleshoot and tune the RF amplifier. The RF system is being constantly improved and the future goal is to increase cyclotron's beam current up to 400 μA, which requires increasing the RF amplifier's power. As a part of this goal, a new RF dummy load was designed.

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THPAL145

Magnetron R&D toward the Amplitude Modulation Control for SRF Accelerator

injection, controls, cavity, SRF

3986

R.A. Rimmer, T. E. Plawski, H. Wang
JLab, Newport News, Virginia, USA
A. Dudas, S.A. Kahn, M.L. Neubauer
Muons, Inc, Illinois, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 and SBIR grant DE-SC0013203
The scheme of using a high efficiency magnetron to drive a superconducting radio frequency (SRF) accelerator cavity needs not only the injection phase locking but also the amplitude modulation to compensate the cavity's microphomics caused cavity voltage change and the beam loading variation. To be able to do a fast and efficient modulation, the magnetron's magnetic field has to be trimmed by an external coil to compensate the frequency pushing effect due to the anode current change [1]. A low eddy current magnetron body has been designed and built [2]. This paper will present the analytical prediction, simulation and experimental results on the 2.45 GHz magnetron test stand with the modulation frequency up to 1 kHz. In addition, the progresses on the injection lock to a copper cavity, new 1497 MHz magnetron prototype, 13 kW high power magnetron test stand development and newly built low level RF (LLRF) controller for the amplitude modulation will be reported.
[1] M. Neubauer et al, THPIK123, Proceedings of IPAC 2017, Copenhagen, Denmark
[2] S. A. Kahn et al, THPIK121, Proceedings of IPAC 2017, Copenhagen, Denmark

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THPAL148

Status of High Efficiency Klystron Development in TETD

klystron, cavity, electron, bunching

3993

Y. Okubo, S. Fujii, K. Suzuki, T.E. Tanaka
Toshiba Electron Tubes & Devices Co., Ltd (TETD), Tochigi, Japan

TETD (Toshiba Electron Tubes and Devices Co., Ltd.) has been developing a high efficiency klystron improved bunch quality by the multi-stage of core oscillation design. For feasibility study, an S-band 7.5 MW klystron has been designed with the efficiency of more than 60% at 1.8μperveance. The first prototype was fabricated by modifying the interaction section of a commercial model to enhance the efficiency from 45% to 60%. The klystron was tested in June 2017, and 57% of efficiency at 6 MW output power was demonstrated. We are developing the second prototype which has the improved design for the higher efficiency at 7.5 WM output power. The design details and the test results of the first prototypes are presented.

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THPAL152

Study of X-Band Phase Shifter Using Ferrite Material

cavity, GUI, coupling, insertion

4005

Y.L. Jiang, D.Z. Cao, H.B. Chen, J. Shi, P. Wang, H. Zha
TUB, Beijing, People's Republic of China

Ferrite has the feature of the permeability depended on the external static magnetic field, thus could be used to shift the phase of the propagating radio frequency (RF) signal. In this paper, we introduce a novel design of ferrite-based RF phase shifter. The design changes the resonant frequency of a ferrite-filled pill-box cavity to implement the phase changing. This design has a lower local RF field and a higher sensitivity on the phase changing than those of waveguide phase shifter, which may bring advantages such as higher power capacity, fast changing speed and lower insertion loss. Theory and simulation results are also presented in this paper.

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THPAL157

Investigation of Transverse Wakefield and Beam Break Up Effect in Irradiation Linacs

cavity, wakefield, experiment, linac

4020

X.C. Meng, H.B. Chen, J. Shi, Z.H. Wang, H. Zha, S.X. Zheng
TUB, Beijing, People's Republic of China
G.H. Li, J.S. Liu, Y.H. Liu
NUCTECH, Beijing, People's Republic of China

Study of beam break up effect in linacs has been done in recent years. The beam-induced high order dipolar modes, especially the TM11-like mode were investigated for the linacs both in travelling wave and backward trav-elling wave. Measurements of beam-break up in a travel-ling wave linac were carried out and results are discussed. Moreover, a theoretical model was developed for the irradiation linacs to study the detailed interaction be-tween the transverse wakefield and the electron beam.

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THPAL158

Development of an Half-Cell Accelerating Structure in Tsinghua

cavity, GUI, alignment, radiation

4023

M.M. Peng, W. Gai, J. Shi, Z.H. Wang, H. Zha
TUB, Beijing, People's Republic of China

The half-cell high gradient accelerating structure is attractive for its easy manufacturing and good alignment. A structure with 12 cells has been designed for the frequency of 11.424 GHz and a cold test will be conducted. Two different mechanical factory manufacture with same machining drawing and the results will be compared.

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THPMF012

Tapered Flying Radiofrequency Undulator

undulator, electron, FEL, ECR

4059

S.P. Antipov, S.V. Kuzikov, A. Liu
Euclid TechLabs, LLC, Solon, Ohio, USA
S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

Funding: DOE SBIR DE-SC0017145
The x-ray free electron laser (x-FEL) efficiency, measured as a fraction of the electron beam power converted into light, is typically below 0.1% for most of the x-FEL facilities presently in operation. Undulator tapering techniques can be used to improve the conversion efficiency by 1-2 orders of magnitude. However at present there are no robust tapered undulator x-FEL schemes operating at 10% efficiency. In this paper we report on the development of tapered radiofrequency (RF) undulator. An RF undulator is a microwave waveguide in which strong RF field is excited that interacts with a charged particle beam forcing it to radiate coherent x-rays while undergoing a wiggling motion. RF undulators are attractive for use in x-FELs due to their large beam aperture and a short undulator period. Strongly tapered RF undulators (with tapering of a wavelength) due to non-resonant trapping regime allow keeping high overall XFEL efficiency being driven by laser plasma accelerated beams usually having high enough current but large energy spread (1-10%).

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THPMF022

Study of Possible Beam Losses After Post-Linac Collimation at European XFEL

undulator, radiation, FEL, vacuum

4092

S. Liu, W. Decking
DESY, Hamburg, Germany
F. Wolff-Fabris
XFEL. EU, Schenefeld, Germany

The European XFEL has been operating with the undulator beam line SASE1 and SASE3 since April 2017 and February 2018, respectively. Despite of the fact that the post-linac collimation has collimated the beam halo to ~20 σ level*, relative high radiation doses have been measured especially in the diagnostic undulator (DU) section**. In order to find the sources of beam losses after post-linac collimation, BDSIM simulations have been performed. In this paper, we will first present the possible losses generated by the wire scanners upstream of the undulators during a scan. The simulation results will be compared with the measured doses along SASE1 and SASE3 undulators. Based on the simulation results, we will estimate the frequency for wire scanner opera-tions. Besides, the simulations with large extension of beam halo hitting the vacuum chamber aperture transition will also be presented. Finally, other possible radiation dose sources will be discussed.
* S. Liu et al., in Proc. of FEL 2017, Santa-Fe, USA, Aug. 2017, paper TUP003.
** F. Wolff-Fabris et al.,IPAC-2018 contribution.

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THPMF028

Coherent Stacking Scheme for Inverse-Compton Scattering at MHz Repetition Rates

laser, cavity, coupling, feedback

4103

P. Piot, D. Mihalcea
Northern Illinois University, DeKalb, Illinois, USA
T.J. Campese, A.Y. Murokh
RadiaBeam Systems, Santa Monica, California, USA
D. Mihalcea, P. Piot, J. Ruan
Fermilab, Batavia, Illinois, USA

Funding: Work sponsored by the DNDO award 2015-DN-077-ARI094 to Northern Illinois University and US DOE contract DE-AC02-07CH11359 to Fermilab.
An experiment to produce 1-MeV gamma rays via Compton back-scattering of infrared photons on 250-MeV electron bunches is currently in preparation at the Fermilab Accelerator Science & Technology (FAST) facility. To increase the gamma-ray flux the energy of the infrared laser pulses are planned to be amplified within the interaction region using a resonant cavity. This passive amplifier composed of a Fabry-Perot cavity will allow the laser pulse bunches to coherently and constructively stack. Our estimates, based on theoretical models, show that the laser pulse energy can be increased from approximately 1-2 mJ at the exit of the last active amplifier to 5 -10 mJ at the interaction point when the laser repetition rate is set at the nominal value of 3 MHz. This paper details the cavity design option(s) and associated wave-optic simulations.

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THPMF048

Bunch Length Measurements Using CTR at the AWA with Comparison to Simulation

experiment, laser, gun, electron

4166

N.R. Neveu
IIT, Chicago, Illinois, USA
S.P. Antipov
Euclid TechLabs, LLC, Solon, Ohio, USA
A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA
J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Argonne, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
In this paper we present electron bunch length measurements at the Argonne Wakefield Accelerator (AWA) photoinjector facility. The AWA accelerator has a large dynamic charge density range, with electron beam charge varying between 0.1 nC - 100 nC, and laser spot size diameter at the cathode between 0.1 mm - 18 mm. The bunch length measurements were taken at different charge densities using a metallic screen and a Martin-Puplett interferometer to perform autocorrelation scans of the corresponding coherent transition radiation (CTR). A liquid helium-cooled 4K bolometer was used to register the interferometer signal. The experimental results are compared with Impact-T and OPAL-T numerical simulations.

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THPMF049

Photoinjector Optimization Studies at the AWA

emittance, laser, experiment, gun

4169

N.R. Neveu
IIT, Chicago, Illinois, USA
J. Larson, J.G. Power
ANL, Argonne, Illinois, USA
L.K. Spentzouris
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357.
With a variable charge range of 0.1 nC - 100 nC, the Argonne Wakefield Accelerator facility (AWA) has a unique and dynamic set of operating parameters. Adjustment of the optics and occasionally the rf phases is required each time the bunch charge is changed. Presently, these adjustments are done by the operator during each experiment. This is time consuming and inefficient, more so at high charge and for complex experimental set ups. In an attempt to reduce the amount of time spent adjusting parameters by hand, several optimization methods in simulation are being explored. This includes using the well-known Genetic Algorithm (NSGA-II), incorporated into OPAL-T. We have also investigated a model-based method and novel structure based algorithms developed at ANL. Ongoing efforts include using these optimization methods to improve operations at the AWA. Simulation results will be compared to measured beam parameters at the AWA, and one optimization method will be selected for use in guiding operations going forward.

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THPMF055

Ion Instability Simulation in the HEPS Storage Ring

electron, storage-ring, emittance, lattice

4189

S.K. Tian, Y. Jiao, N. Wang
IHEP, Beijing, People's Republic of China
K. Ohmi
KEK, Ibaraki, Japan

The High Energy Photon Source (HEPS), a kilometre scale storage ring light source, with a beam energy of 6 GeV and transverse emittances of a few tens of pm.rad, is to be built in Beijing and now is under design. We investigate the ion instability in the storage ring with high beam intensity and low-emittance. We performe a weak-strong simulation to show characteristic phenomena of the instability in the storage ring.

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THPMF059

Simulation Studies of Beam Commissioning and Expected Performance of the SPring-8-II Storage Ring

emittance, quadrupole, lattice, sextupole

4203

Y. Shimosaki
JASRI, Hyogo, Japan
K. Soutome, M. Takao
JASRI/SPring-8, Hyogo-ken, Japan
H. Tanaka
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

In the SPring-8 upgrade project, the 5-bend achromat lattice is adopted for achieving a very low emittance of 157 pm.rad at 6 GeV. Since the dynamic aperture (DA) and the beam performance become sensitive against errors due to the strong quadrupoles and sextupoles, we carried out tracking simulations to evaluate the tolerance of machine imperfections such as the misalignment, magnetic field errors, the BPM offset, etc. It is found that the first-turn-steering (FTS) with the use of single-pass BPM's is indispensable because even under strict (but attainable) tolerances the beam cannot be stored without steering kicks. We then confirmed that after the FTS a sufficiently large DA can be obtained for accumulating the beam by the off-axis injection. By performing the orbit and optics corrections for the stored beam, we can finally achieve an emittance value of 160 ~ 180 pm.rad, being close to the design value. We also found that a naive application of the SVD algorithm to orbit corrections yields unwanted local bumps between BPM's and this deteriorates the vertical emittance. A possible scheme to avoid such local bumps by effectively interpolating the measured orbit will be discussed.

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THPMF060

Touschek Beam Loss Simulation for Light Source Storage Rings

electron, scattering, storage-ring, coupling

4206

M. Takao, K. Soutome
JASRI/SPring-8, Hyogo-ken, Japan
Y. Shimosaki
JASRI, Hyogo, Japan
K. Soutome, H. Tanaka
RIKEN SPring-8 Center, Hyogo, Japan

In light source storage rings, it is important to know the distribution of lost electrons due to the Touschek scattering for protecting insertion devices (IDs) from radiation damage. This will become crucial especially in future light sources where narrow gap in-vacuum IDs are normally used. While the Touschek scattered electron begins to oscillate in the horizontal direction with the amplitude proportional to the dispersion at the scattering point and to the momentum deviation after scattering, the motion is converted into the vertical direction due to the betatron coupling and some of the scattered electrons are lost at the narrow gaps of in-vacuum IDs. The momentum deviation by the Touschek scattering reaches 5% more, and according to which the vertical oscillation is more excited. Hence electrons even scattered at small horizontal dispersion are also lost at narrow gap IDs. We carried out computer simulations by taking the present SPring-8 storage ring and a planned 3GeV low-emittance ring as examples. The results and possible measures for ID protection will be presented.

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THPMF069

Perturbation to Stored Beam by Pulse Sextupole Magnet and Disturbance of the Sextupole Magnetic Field in Aichi Synchrotron Radiation Center

synchrotron, radiation, synchrotron-radiation, injection

4232

A. Mochihashi
KIT, Eggenstein-Leopoldshafen, Germany
M. Fujimoto, M. Katoh
UVSOR, Okazaki, Japan
M. Hosaka, M. Hosaka, Y. Takashima, Y. Takashima, K. Y. Yamamura
Nagoya University, Nagoya, Japan
M. Hosaka, H. Ohkuma, Y. Takashima
Aichi Synchrotron Radiation Center, Aichi, Japan
M. Katoh
Sokendai - Okazaki, Okazaki, Aichi, Japan
H. Ohkuma
JASRI/SPring-8, Hyogo-ken, Japan

In the Aichi synchrotron radiation center (Aichi-SR), a pulse sextupole magnet (PSM) has been installed as a pulse magnet for beam injection. This leads to the injection scheme without using a bump orbit and stable supply of the synchrotron radiation. In Aichi-SR we have performed usual injection scheme with 4 kicker magnets and making the bump. Because the circumference of the Aichi-SR is only 72 m, 3 beam lines are inside the bump. The Aichi-SR has performed top-up operation since its public open, so it is a crucial subject to eliminate the disturbance of the synchrotron radiation during the injection. We have installed the PSM in 2015 and developed the beam study continuously. At present, however, a perturbation to the stored beam by the PSM still has been observed and is not acceptable. We have performed beam diagnostic experiment and concluded that an additional dipole kick affects the beam. From the magnetic field measurement data, we have discussed the source of the additional kick; most likely is an eddy current on the Ti coating inside the ceramics duct of the PSM. The beam diagnostics experiment and the magnetic field measurement will be discussed in the presentation.
Present affiliation of the first auther : Karlsruhe Institute of Technology

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THPMF074

Study of the Saturation of Radiation Energy Caused by the Space Charge Effect in a Compact THz Coherent Radiation Source

electron, radiation, undulator, laser

4245

S. Krainara, Chatani, S. Chatani, T. Kii, H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Funding: Institute of Advanced Energy, Kyoto University
To generate an intense quasi-monochromatic Terahertz Coherent Undulator Radiation (THz-CUR), a compact linac system, which employs a magnetic electron bunch compressor with a beam energy of 4.6 MeV, has been constructed at Kyoto University. The THz-CUR has suc-cessfully been generated in a frequency range from 0.16 to 0.65 THz with a bunch charge of 60 pC. The maximum micro-pulse energy of THz radiation was observed higher than 1 μJ at 0.16 THz with 160 pC. However, when a bunch charge was higher than 80 pC, the micro-pulse energy of THz radiation gradually went to the saturation and obviously at the bunch charge higher than 110 pC because of the bunch lengthening and degradation of electron beam quality due to the space charge effect. The dependence of a bunch length on a bunch charge has been studied by GPT simulation and compared with CTR and CUR experiments. The trends of the measured results from CUR and CTR are in good agreement with the GPT simulation.

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THPMF078

Simulation of Trajectory Correction in Early Commissioning of the Advanced Light Source Upgrade

MMI, lattice, sextupole, closed-orbit

4256

T. Hellert, J.-Y. Jung, S.C. Leemann, H. Nishimura, D. Robin, F. Sannibale, C. Steier, C. Sun, C.A. Swenson, M. Venturini
LBNL, Berkeley, California, USA

Funding: *Work supported by the Director of the Office of Science of the US Department of Energy under Contract no. DEAC02-05CH11231.
The ALS upgrade into a diffraction-limited soft x-rays light source requires a small emittance, which is achieved by much stronger focusing than in the present ALS. Very strong focusing elements and a relatively small vacuum chamber make the required rapid commissioning a significant challenge. This paper will describe the progress towards a start-to-end simulation of the machine commissioning and present first simulation results.

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THPMF085

Beam Dynamics Simulation of the Solenoid Sextupole Error in the LCLS-II Injector

sextupole, emittance, solenoid, electron

4277

J. Qiang
LBNL, Berkeley, California, USA
S.D. Anderson, D. Dowell, P. Emma, J.F. Schmerge, M.D. Woodley, F. Zhou
SLAC, Menlo Park, California, USA

The LCLS-II injector is a high brightness, high-repetition rate RF injector that consists of a 186 MHz VHF photo-electron gun, a focusing solenoid, a buncher cavity, another focusing solenoid, and a superconducting accelerating cryomodule to boost the electron beam energy to about final 100MeV. The solenoids provide transverse focusing and emittance compensation for the electron beam. However, in reality, the solenoid is not perfect due to manufacturing errors. Especially, the sextupole error in the solenoid field, which can cause significant beam emittance growth. In this paper, we report on the beam dynamics study of the effects of sextupole errors in the current LCLS-II injector.

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THPMF086

Reliability Improvement on Wiggler Period Averaging Approximation

wiggler, FEL, laser, plasma

4281

K. Hwang, J. Qiang
LBNL, Berkeley, California, USA

Funding: US Department of Energy under Contract no. DEAC02-05CH11231
As the wiggler period averaging is subject to reliability issue, many efforts on FEL codes without such approximations are made at the cost of heavier computation loads. However, efforts toward increasing the reliability of such approximation are few. In this report, we present a new capability of IMPACT code suite based on such approximation with the addition of perturbative corrections to wiggler period averaging error.

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THPMK001

Creating Two-Pulse Beams from a Photoinjector for Two Color FEL or Beam Driven PWFA Experiments

linac, gun, emittance, cathode

4294

J. Andersson, J. Björklund Svensson, M. Kotur, F. Lindau, S. Thorin
MAX IV Laboratory, Lund University, Lund, Sweden

The MAX IV linac is investigated as a FEL driver in the SXL project, but there is also an ongoing investigation in using the linac as a driver for beam driven plasma wakefield acceleration experiments. From both these applications, double pulses from the photoinjector within the same RF period is desired. In this paper we discuss the possibilities of using the current photoinjector at MAX IV as driver and show simulations results from the pre-injector, both for FEL applications and for PWFA applications.

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THPMK004

Pulse-Picking by Resonant Excitation (PPRE) for Timing Users at the MAX IV 3 GeV Storage Ring

emittance, photon, storage-ring, cavity

4300

T. Olsson, Å. Andersson, D.K. Olsson
MAX IV Laboratory, Lund University, Lund, Sweden

At synchrotron light storage rings there is demand for serving both high-brilliance and timing users simultaneously. At many rings this is commonly achieved by operating fill patterns with gaps of sufficient length, but this is not favorable for rings that operate with passive harmonic cavities to damp instabilities and increase Touschek lifetime by lengthening the bunches. For such rings, gaps in the fill pattern could severely reduce the achievable bunch lengths. For the MAX IV 3 GeV storage ring, sufficient bunch lengthening is also essential for conserving the ultralow emittance and reducing heat load on vacuum components at high current. It is therefore of interest to study methods to serve timing users while operating without gap in the fill pattern. Once such method is PPRE, where the transverse emittance of one bunch in the bunch train is increased by an incoherent betatron excitation. This paper presents simulations for the MAX IV 3 GeV storage ring and discusses the machine requirements as well as the achievable performance for timing users.

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THPMK007

Surface Acoustic Wave Enhancement of Photocathodes

electron, cathode, laser, photon

4304

R.P. Johnson
Muons, Inc, Illinois, USA
A. Afanasev, B. Dong, M. E. Zaghloul
GWU, Washington, USA

Funding: Work supported by DOE HEP STTR Grant DE-SC0017831
Numerical simulations and fabrication techniques are being used to investigate the use of surface acoustic waves to suppress electron-hole recombination on the surface of GaAs photocathodes in order to increase the quantum efficiency for polarized and unpolarized electron beam generation.

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THPMK012

Reduction of Dynamic Multipole Content in Insertion Devices Using Flat Wires

multipole, electron, undulator, MMI

4313

T.Y. Chung, S.D. Chen, M.-S. Chiu, S.J. Huang, C.-S. Hwang, J.C. Jan, C.Y. Kuo, Y.T. Li, C.Y. Wu
NSRRC, Hsinchu, Taiwan
C.-S. Hwang
NCTU, Hsinchu, Taiwan

Multipole errors of an insertion device are generally corrected based on measurements and analysis of the magnetic field integrals. Multipole components in a strong and narrow non-uniform field of an insertion device appear as dynamic multipoles. Flat wires were installed and commissioned to determine if the dynamic multipoles can be eliminated in an APPLE-II type undulator. In this work, we will discuss and compare the reduction of the dynamic multipole content and it's beam dynamics effects with the flat wire through an analysis of field calculations and beam-based measurements in the storage ring.

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THPMK016

Simulation Study of the NSRRC High Brightness Linac System and Free Electron Laser

linac, FEL, undulator, electron

4329

W.K. Lau, C.H. Chen, H.P. Hsueh, N.Y. Huang
NSRRC, Hsinchu, Taiwan
J. Wu
SLAC, Menlo Park, California, USA

A 263 MeV linac system has been designed to provide a high brightness electron beam for the NSRRC VUV FEL test facility. This system is equipped with a dogleg with linearization optics to compensate the effects of nonlinear energy chirps introduced into the system by the chirper linac voltage during bunch compression. In this study, we performed start-to-end simulation to illustrate the capability of this linac system to generate a beam that can be used to drive a SASE FEL to saturation within reasonable undulator length. It has been demonstrated that, for a 200 pC beam, such FEL has a saturated output power of ~200 MW at 6-m undulator length. Further optimization of bunch current profile and momentum spectrum is required.

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THPMK022

Simulation for THz Coherent Undulator Radiation from Combination of Velocity Bunchings

radiation, bunching, electron, undulator

4345

Y. Sumitomo, K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, Y. Takahashi, T. Tanaka
LEBRA, Funabashi, Japan

We study the effect of a combination of velocity bunchings and its application to THz coherent undulator radiation at LEBRA, Nihon U. by simulations. The velocity bunching is a technique that is commonly used to make the bunch length shorter at lower energies. However, since one velocity bunching has a correlation between bunch energy and length, we may not have so much room to change energies to obtain different coherent radiation wavelengths. Hence we propose a combination of velocity bunchings, that relaxes the restrictive correlation. We have three 4m traveling-wave accelerator tubes at LEBRA, Nihon U. The undulator is installed after the acceleration tubes and 2 x 45 degree bending magnets. Since the design of current undulator requires less than 25 MeV beam energy to obtain the radiation at THz region, the velocity bunching is reasonable for coherent radiation. We show the simulation results of a combination of velocity bunchings of the three tubes and the magnetic bunching at bending magnets, suitable for the coherent undulator radiation.

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THPMK023

Coherent Transition Radiation Generated from Transverse Electron Density Modulation

radiation, electron, detector, experiment

4348

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
A.I. Benediktovitch
BSU, Minsk, Belarus, Belarus
S.N. Galyamin, A.V. Tyukhtin
Saint Petersburg State University, Saint Petersburg, Russia
P. Piot
Fermilab, Batavia, Illinois, USA

Coherent Transition radiation (CTR) of a given frequency is commonly generated with longitudinal electron bunch trains. In this paper we present a study of CTR production from electron transverse density modulation. We demonstrate via numerical simulations a simple technique to generate THz-scale frequencies from mm-scale transversely separated electron beamlets. The results and a potential experimental setup are discussed.

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THPMK034

Study on Effect of Phase Shifter on FEL Intensity at PAL-XFEL

FEL, undulator, electron, radiation

4372

C.H. Shim
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.H. Hong, H. Yang
PAL, Pohang, Kyungbuk, Republic of Korea

In the PAL-XFEL, the phase shifters are installed be-tween the undulator modules to match the phase of the electron beam and the FEL radiation field at the entrance of next undulator. By varying the phase shifter gap, the FEL intensity measured at the QBPM oscillates and sine curve fitting can be applied to it for optimizing the FEL intensity. However, the optimal gap determined from fitting result is slightly different from the gap at which the maximum intensity is measured because distorted shapes are appeared from some phase shifters. In this presentation, we report and discuss the experimental results of phase shifter gap scanning with simulation results.

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THPMK049

New Geometrical-Optimization Approach using Splines for Enhanced Accelerator Cavities' Performance

controls, cavity, impedance, accelerating-gradient

4395

M.H. Nasr, S.G. Tantawi
SLAC, Menlo Park, California, USA

Over the past decades accelerator scientists made a huge effort in advancing the technology of particle accelerators, which lead to state-of-the-art fabrication techniques as well as simulation tools. Combining these advancements with the large boosting in computing speed provides large flexibility and motivation to investigate new accelerator geometries. In this paper, we describe a new optimization approach for the geometry of accelerating cells. This approach uses a set of control points with variable positions to control a non-uniform rational B-spline (NURBS), which describes the cavity shape. The positions of the control points are then optimized using differential-evolution optimization to maximize/minimize a defined optimization function, which is defined by the user and depends on the cavity parameters such as the shunt impedance, wall losses, peak surface fields…etc. This optimization approach leads to accelerator geometries with enhanced performance and very smooth surface fields.

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THPMK053

Simulation for LCLS-II Hard X-ray Self Seeding Scheme

undulator, FEL, photon, electron

4406

C. Yang, Y. Feng, J. Krzywinski, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
SLAC, Menlo Park, California, USA
H.X. Deng
SINAP, Shanghai, People's Republic of China
D.H. He
USTC/NSRL, Hefei, Anhui, People's Republic of China
Y. Hong, B. Yang
University of Texas at Arlington, Arlington, USA
X.F. Wang
CIAE, Beijing, People's Republic of China
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea
G. Zhou
IHEP, Beijing, People's Republic of China

Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Oﬃce of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Typical SASE FELs have poor temporal coherence because of starting from shot noise. Self-seeding scheme is an approach to improve the longitudinal coherence. The single crystal monochromator self-seeding has been in successful operation in LCLS. For the high repetition rate LCLS-II machine, for damage consideration, it was initially proposed to have a two-stage self-seeding scheme, yet we have found the two-stage self-seeding scheme has no advantage over one-stage self-seeding scheme. In this paper, we investigate the optimal self-seeding conﬁguration of LCLS-II for different photon energies, and present a comparison between one-stage and two-stage self-seeding scheme of LCLS-II.

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THPMK055

Self Seeding Scheme for LCLS-II-HE

emittance, electron, FEL, undulator

4414

C. Yang, Y. Feng, J. Krzywinski, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
SLAC, Menlo Park, California, USA
H.X. Deng, X.F. Wang
SINAP, Shanghai, People's Republic of China
D.H. He
USTC/NSRL, Hefei, Anhui, People's Republic of China
Y. Hong, B. Yang
University of Texas at Arlington, Arlington, USA
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea
G. Zhou
IHEP, Beijing, People's Republic of China

Funding: The work was supported by the US Department of Energy (DOE) under contract DE-AC02-76SF00515 and the US DOE Oﬃce of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Self-seeding is a reliable approach to generate fully coherent FEL pulses. Hard X-ray self-seeding can be realized by using a single crystal in Bragg transmission geometry. However, for a high repetition rate machine, the heat load on the crystal may become an issue. In this paper, we will study the facility performance of LCLS-II-HE by numerical simulations, and discuss the heat load and optimal undulator baseline conﬁguration of LCLS-II-HE self-seeding scheme, and study the emittance tolerance of the LCLS-II-HE.

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THPMK060

Start-to-End Simulations of the CLARA FEL Test Facility

FEL, electron, undulator, laser

4430

D.J. Dunning, D. Angal-Kalinin, A.D. Brynes, L.T. Campbell, H.M. Castaneda Cortes, J.K. Jones, J.W. McKenzie, N. Thompson, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
D. Angal-Kalinin, A.D. Brynes, D.J. Dunning, J.K. Jones, J.W. McKenzie, B.W.J. MᶜNeil, N. Thompson, P.H. Williams
Cockcroft Institute, Warrington, Cheshire, United Kingdom
L.T. Campbell, B.W.J. MᶜNeil, P.T. Traczykowski
USTRAT/SUPA, Glasgow, United Kingdom
B.S. Kyle
University of Manchester, Manchester, United Kingdom
B.S. Kyle
UMAN, Manchester, United Kingdom
J.D.A. Smith
TXUK, Warrington, United Kingdom

CLARA is a new FEL test facility being developed at STFC Daresbury Laboratory in the UK, aiming to deliver advanced FEL capabilities including few-cycle pulse generation and Fourier transform limited output. Commissioning is underway on the front-end (photo-injector and first linac) while the later stages are being procured and assembled. Start-to-end (S2E) simulations of the full facility are presented, including optimisation of the accelerator setup to deliver the required properties of one of the electron beam modes specified for FEL operation. FEL simulations are performed using the Genesis 1.3 and Puffin codes and the results are compared.

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THPMK070

Optimization for the Two-Stage Hard X-Ray Self-Seeding Scheme the SCLF

FEL, undulator, radiation, electron

4460

T. Liu, C. Feng, D. Wang, X. Wang, K.Q. Zhang
SINAP, Shanghai, People's Republic of China

Funding: Work supported by the National Natural Science Foundation of China 11475250 and 11605277, National Key Research and Development 2016YFA0401901 and Youth Innovation Promotion Association CAS 2015209.
Self-seeding mode has been demonstrated a great advantage for the achievement of a high brightness X-ray with a pure spectrum. Single-bunch self-seeding scheme with wake monochromators is adopted for the realization of the hard X-ray FEL at the Shanghai Coherent Light Facility (SCLF). Limited by the heat-loading of the monochromator, the two or multiple stages self-seeding scheme is required. In this contribution, we present a basic two-stage scheme design and optimization for the generation of the photon energy range of 3 keV to 15 keV at the line FEL-I of the SCLF. Simulation results show the peak power and pulse energy each stage, which illustrates the loaded energy required of the crystal monochromator as a pointcut of its following thermal analysis. The electron beam energy used in the study is 8 GeV and the central photon energy is 12.4 keV.

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THPMK076

Longitudinal Shaping for Beam-Driven Plasma Wakefield Accelerators

electron, linac, FEL, plasma

4477

Z. Wang, K.Q. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
S. Huang, W. Lu
TUB, Beijing, People's Republic of China

The generation of high quality driven electron beam (high peak current and small beam size) is quite important for the beam-driven plasma accelerator. Besides, a linearly ramped, more exactly, the triangular current distribution is more suitable. In this paper, by adjusting the phase and the amplitude of the harmonic linearizer, the linear ramped current distribution electron beam is generated by the FEL linac. The CSR introduced emittance growth and the jitters of the electron are researched. The electron beam generated by the ramped driven beam in the plasma is researched as well.

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THPMK077

The Preliminary Experiment Studies for Soft X-Ray Self-Seeding System Design of SCLF Facility

photon, FEL, experiment, electron

4481

K.Q. Zhang, C. Feng, D. Wang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

The preliminary experiment studies for soft x-ray self-seeding system design of SCLF facility have been pre-sented in this paper. Some practical problems and pre-engineering design have been studied for the experimental prepare of soft x-ray self-seeding for the future SCLF facility. The monochromator system designs in this paper include optical structure, optical parameters and mechanical design. The designed optical system has an optical resolution of 1/10000 at the photon energy of 700-1300eV based on the optical simulation. To make the system satisfy the experimental requirements, mechanical install requirements and install precisions are also analysed. Considering the actual varies errors, the errors analyses such as the surface errors of the optical mirror and the machining errors of the VLS grating are also carried out. In conclusion, preliminary experimental studies including system design and varies engineering requirements are introduced to make sure that the presented design is reliable for final soft x-ray self-seeding experiment of SCLF facility.

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THPMK078

Corrugated Structure as a Linearizer in High Repetition Rate X-Ray Free Electron Laser Source

electron, FEL, linac, laser

4485

Z. Wang, C. Feng, D. Huang, K.Q. Zhang, M. Zhang
SINAP, Shanghai, People's Republic of China

A feasible method is proposed to compensate the high order mode (HOM) of the RF field, linearize the bunch compression process in the high repetition rate x-ray free electron laser source. In the proposed scheme, the corrugated structure is used in the superconducting linac to linearize the longitudinal phase space of the electron beam. The results show that the peak current of the electron beam will be increased from about 1 kA to over 2 kA with the charge of 100 pC.

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THPMK100

Setup for Cooled GaAs Cathodes With Increased Charge Lifetime

cathode, electron, cryogenics, vacuum

4542

T. Eggert, J. Enders, M. Espig, Y. Fritzsche, N. Kurichiyanil, M. Wagner
TU Darmstadt, Darmstadt, Germany

Funding: DFG (GRK 2128) BMBF (05H15RDRB1)
GaAs photocathode lifetime is limited, and to ensure re- liable operation for high power-applications it is necessary to maximize its charge lifetime. By using a cryogenic sub- volume it is expected to improve the local vacuum condi- tions due to cryogenic adsorption of reactive residual gas molecules. Yielding an enhanced lifetime of the negative- electron-affinity surface of the cathode. Furthermore the cooling of the cathode itself ishould allow higher laser power deposition in the material. Introducing an electrostatic bend is expected to reduces the ion-backbombardment on the cath- ode surface. A dedicated set-up is being developed at the Photo-CATCH test facility in Darmstadt, Germany to measure the charac- teristics of such a cryogenic source. This contribution updates the report given at PSTP 2017.

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THPMK111

Negative Electron Affinity Gallium Arsenide Photocathodes Based on Optically Resonant Nanostructure

cathode, resonance, electron, experiment

4575

S. Zhang, M. Poelker, M.L. Stutzman
JLab, Newport News, Virginia, USA
X. Peng, J. Zou
East China University of Science and Technology, Shanghai, People's Republic of China

Funding: DOE
We report the design and fabrication of a new type of negative electron affinity (NEA) gallium arsenide (GaAs) photocathode with optically resonant nanostructures. We observed a significant enhancement of the quantum effi-ciency (QE) from the GaAs photocathode with nanowire arrays (NWA) due to the Mie resonance effect within the intended wavelength range. Theoretical calculations of the expected reflectance behaviour together with experi-mental results of optical and photoemission characteris-tics are presented.

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THPMK127

Terahertz Smith-Purcell Radiation From the High-Harmonic Component of Modulated Electron Beam From Dielectric Structure

radiation, electron, bunching, wakefield

4617

S.M. Jiang, Z.G. He, Q.K. Jia, W.W. Li, L. Wang
USTC/NSRL, Hefei, Anhui, People's Republic of China
D. He
Anhui Electrical Engineering Professional Technique College, Hefei, People's Republic of China

Funding: Supported by National Nature Science Foundation of China(11705198, 11775216)
In this paper, a new radiation scheme, which adopts the high order harmonic of modulated electron beam from dielectric loaded waveguide to excite the Smith-Purcell terahertz (THz) radiation, is proposed and in-vestigated by numerical simulations. The results show that the radiation with frequency close to 1.0 THz is generated, while, the fundamental bunching frequency of electron beam is 0.28 THz. Thus, this scheme offer a new method to get the higher frequency THz radiation.

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THPMK129

Lattice Tweaking Using A Tune Knob Based On Global Mechanism

storage-ring, quadrupole, injection, lattice

4620

S.W. Wang, B. Li, J.L. Li, W.B. Wu, W. Xu, X. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China
J.L. Li
IHEP, Beijing, People's Republic of China

The transverse tunes are important parameters for a storage ring and tune knobs are used to adjust the tunes in a specific range. Usually for large rings, a set of quadrupoles is set on the straight sections for the use of tune knob. A tune knob has been designed for the HLS-II storage ring without affecting the twiss parameters of the injection section. This paper introduces the design and online test of this tune knob. The quadrupoles are adjusted according to the simulation results and the tunes are measured and calibrated. The online test results show that the tune knob design works well on the HLS-II storage ring and can be applied for various machine studies.

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THPMK138

Power Enhancement of Free-Electron Lasers Oscillators With the Natural Gradient of a Planar Undulators

FEL, undulator, electron, radiation

4632

Z. Zhao, L.J. Chen, Q.K. Jia, H.T. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by National Natural Science Foundation of China (No. 21327901, 11205156)
Transverse Gradient Undulator (TGU) has been proposed with the initial purpose of mitigating the gain degradation in free electron laser (FEL) oscillators driven by beams with a large energy spread. However, a special-designed TGU with a fixed transverse gradient is required to enhance the gain. In this paper, we investigate using the natural field gradient of a normal planar undulator instead of a TGU to enhance the FEL oscillator (FELO) power. In this method, the beam is first vertically dispersed by a dogleg and then the dispersed beam passes through a normal undulator with a vertical off-axis orbit. Theoretical analysis and numerical simulation based on parameters of FELiChEM are presented. It demonstrates that this scheme can enhance the FEL power with careful optimization of dispersion strength and vertical beam orbit offset, especially when the energy spread is relatively large.

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THPMK139

Design of 9/6 MeV S-band Electron Linac Structure with 1.5 Bunching Cells

coupling, linac, bunching, electron

4635

Y. Joo, P. Buaphad, H.R. Lee
University of Science and Technology of Korea (UST), Daejeon, Republic of Korea
S.C. Cha, Y. Kim
KAERI, Daejon, Republic of Korea

Funding: University of Science and Technology of Korea
The Korea Atomic Energy Research Institute (KAERI) has been developing several 9/6 MeV dual energy S-band RF electron linear accelerators (linacs) for non-destructive testing such as container inspection system. Until now the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half-cell. The optimization of Q-factor and flatness of electric field along the linac structure can be obtained by adjusting diameters of bunching and power coupling cells. By adjusting gap of the first side-coupling cell, we can optimize the field ratio between the bunching cells and normal accelerating cells. In this paper, we describe design concepts of a 9/6 MeV linac with 1.5 bunching cells as well as optimization of RF parameters such as the quality factor, resonance frequency, and electric field distribution.

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THPML006

Using Drive Rods in Inductions Cells to Reduce the Beam Break Up Instability

impedance, induction, wakefield, cavity

4658

N. Pogue, T.L. Houck, B.R. Poole
LLNL, Livermore, California, USA

The Beam Breakup Instability is a critical effect to reduce in high current induction accelerators. The RF modes generated inside the induction cells can deflect or degrade subsequent beam traversing the cell. Significant effort has been invested in minimizing the effect over several decades. One mechanism that is known to reduce the transverse impedance, the main observable experimentally which directly relates to the BBU amplitude, is to introduce ferrites to absorb the fields. Another, less investigated mechanism, is to disturb the modes symmetry by inserting the drive rods at the proper locations in the cell. This paper will show that the drive rods can dramatically reduce the transverse impedance, and will show that simulations are maturing towards predicting this effect. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

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THPML010

Modeling of Diamond Field Emitter Arrays for Shaped Electron Beam Production

electron, gun, emittance, experiment

4668

K.E. Nichols, H.L. Andrews, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA

We present simulations of shaped electron beam production from diamond field emitter array (DFEA) cathodes. DFEAs are arrays of diamond pyramids with bases of the order of 10 microns that produce high current densities. These arrays can be fabricated in arbitrary shapes such as a triangle or a double triangle, so that they produce an inherently shaped beam. These transversely shaped beams can be put through an emittance exchanger to produce a longitudinally shaped electron beam distribution for use with high-transformer ratio wakefield accelerators. Simulations are conducted with MICHELLE. We design cathodes and focusing systems that preserve the beam's shape while transporting it to the emittance exchanger.

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THPML014

A Metamaterial Wagon Wheel Structure for Wakefield Acceleration by Reversed Cherenkov Radiation

wakefield, experiment, acceleration, electron

4681

X.Y. Lu, I. Mastovsky, M.A. Shapiro, R.J. Temkin
MIT/PSFC, Cambridge, Massachusetts, USA
M.E. Conde, C.-J. Jing, J.G. Power, J.H. Shao, E.E. Wisniewski
ANL, Argonne, Illinois, USA

Funding: U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0015566 and the U.S. Department of Energy Office of Science under Contract No. DE-AC02-06CH11357
We present the design and experimental operation on an X-band metamaterial (MTM) wagon wheel structure for wakefield acceleration. The structure was designed and fabricated at MIT, and tested at the Argonne Wakefield Accelerator (AWA) laboratory at Argonne National Lab. The MTM wagon wheel structure is an all-metal periodic structure at 11.4 GHz. The fundamental TM mode has a negative group velocity, so when an electron beam travels through, energy is extracted from the beam by reversed Cherenkov radiation, which was verified in the experiment. Single bunches up to 45 nC were sent through the structure with a beam aperture of 6 mm and generated microwave power up to 25 MW in a 2 ns pulse, in agreement with both the analytical wakefield theory and the numerical CST simulations. Two bunches with a total charge of 85 nC generated 80 MW of microwave power. The structure is scalable to a power extractor of over 1 GW by increasing the structure length from 8 cm to 22 cm.

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THPML027

Longitudinal and Transverse Wakefields Simulations and Studies in Dielectric-Coated Circular Waveguides

electron, wakefield, GUI, radiation

4708

L. Ficcadenti
Rome University La Sapienza, Roma, Italy
A. Biagioni
INFN/LNF, Frascati (Roma), Italy
G. Castorina, D. Francescone, M. Marongiu, M. Migliorati, A. Mostacci, L. Palumbo
Sapienza University of Rome, Rome, Italy

In recent years, there has been a growing interest and rapid experimental progress on the use of e.m. fields produced by electron beams passing through dielectric-lined structures and on the effects they might have on the drive and witness bunches. Short ultra-relativistic electron bunches can excite very intense wakefields, which provide an efficient acceleration through the dielectric wakefield accelerators (DWA) scheme with higher gradient than that in the conventional RF LINAC. These beams can also generate high power narrow band THz coherent Cherenkov radiation. These high gradient fields may create strong instabilities on the beam itself causing issues in plasma acceleration experiments (PWFA), plasma lensing experiments and in recent beam diagnostic applications. In this work we report the results of the simulations and studies of the wakefields generated by electron beams at different lengths and charges passing on and off axis in dielectric-coated circular waveguides. We also propose a semi-analytical method to calculate these high gradient fields without resorting to time consuming simulations.

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THPML042

Integrating the Lorentz Force Law for Highly-Relativistic Particle-in-Cell Simulations

plasma, laser, acceleration, radiation

4734

A.V. Higuera, J.R. Cary
Tech-X, Boulder, Colorado, USA
J.R. Cary
CIPS, Boulder, Colorado, USA

Funding: This work is supported by the DOE under Grants No. DE-SC0011617 and DE-SC0012444, and by DOE/NSF Grant No. DE-SC0012584
Integrating the Relativistic Lorentz Force Law for plasma simulations is an area of current research (*, **, ***). In particular, recent research indicates that interaction with highly-relativistic laser fields is particularly problematic for current integration techniques (****). Here is presented a special-purpose integrator yielding improved accuracy for highly-relativistic laser-particle interactions. This integrator has been implemented in the particle-in-cell code VSim, and the authors present an accuracy and performance comparison with several particle push methods.
* http://aip.scitation.org/doi/abs/10.1063/1.4979989
** https://arxiv.org/abs/1702.04486
*** https://arxiv.org/abs/1710.09164
**** http://aip.scitation.org/doi/abs/10.1063/1.4905523

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THPML043

Optimization of Dielectric Laser-Driven Accelerators

laser, electron, acceleration, plasma

4737

C.P. Welsch, M.G. Ibison, Y. Wei
The University of Liverpool, Liverpool, United Kingdom
M.G. Ibison, Y. Wei, C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom
J.D.A. Smith
TXUK, Warrington, United Kingdom
G.X. Xia
UMAN, Manchester, United Kingdom

Funding: This project has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no 289191.
Dielectric laser-driven accelerators (DLAs) utilizing large electric field from commercial laser system to accelerate particles with high gradients in the range of GV/m have the potential to realize a first particle accelerator ‘on a chip'. Dual-grating structures are one of the candidates for DLAs. They can be mass-produced using available nanofabrication techniques due to their simpler structural geometry compared to other types of DLAs. Apart from the results from optimization studies that indicate the best structures, this contribution also introduces two new schemes that can help further improve the accelerating efficiency in dual-grating structures. One is to introduce a Bragg reflector that can boost the accelerating field in the channel, the other applies pulse-front-tilt operation for a laser beam to help extend the interaction length.

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THPML060

Virtual VELA-CLARA: The Development of a Virtual Accelerator

controls, EPICS, lattice, software

4773

T.J. Price, H.M. Castaneda Cortes, D.J. Dunning, J.K. Jones, B.D. Muratori, D.J. Scott, B.J.A. Shepherd, P.H. Williams
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
R.F. Clarke, G. Cox
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

A Virtual Accelerator (VA) has been developed to mimic the accelerators Versatile Electron Linear Accelerator (VELA) and Compact Linear Accelerator for Research and Applications (CLARA). Its purpose is to test control room applications, run start-to-end simulations with multiple simulation codes, accurately reproduce measured beam properties, conduct 'virtual experiments'and gain insight into ‘hidden beam parameters'. This paper gives an overview into the current progress in constructing this VA, detailing the areas of: developing a 'Virtual EPICS' control system, using multiple simulation codes (both particle tracking and analytic), the development of a ‘Master Lattice' and the construction of a Python interface in which to run the VA.

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THPML061

X-Band Low Q Cavity Beam Position Monitor Study

cavity, FEL, electron, GUI

4777

S.S. Cao
SINAP, Shanghai, People's Republic of China
Y.B. Leng, R.X. Yuan
SSRF, Shanghai, People's Republic of China

The high repetition-rate and high peak brilliance of X-ray free-electron laser (XFEL) allow studying many scientific experiments that have not been feasible. To realize such high performance, a sub-micron beam transverse position measurement is required. The cavity-type beam position monitor (CBPM), as a non-destructive diagnostics tool with high potential in resolution performance, has been applied in different free electron laser facilities (FELs). In this research, an X-band high bandwidth CBPM has been studied and used for pre-research on bunch-by-bunch diagnostic for the pulsed FEL with high repetition-rate. Its bandwidth reaches 300 MHz. Design considerations and simulation results of the CBPM have been discussed and presented in this paper.

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THPML063

Micro-Bunched Beam Production at FAST for Narrow Band THz Generation Using a Slit-Mask

electron, radiation, cavity, quadrupole

4784

J. Hyun
Sokendai, Ibaraki, Japan
D.J. Crawford, D.R. Edstrom, J. Ruan, J.K. Santucci, T. Sen, J.C.T. Thangaraj, R.M. Thurman-Keup
Fermilab, Batavia, Illinois, USA

We discuss simulations and experiments on creating micro-bunch beams for generating narrow band THz radiation at the Fermilab Accelerator Science and Technology (FAST) facility. The low-energy electron beamline at FAST consists of a photoinjector-based RF gun, two L-band superconducting accelerating cavities, a chicane, and a beam dump. The electron bunches are lengthened with cavity phases set off-crest for better longitudinal separation and then micro-bunched with a slit-mask installed in the chicane. We carried out the experiments with 30 MeV electron beams and detected signals of the micro-bunching using a skew quadrupole magnet in the chicane. In this paper, the details of micro-bunch beam production, the detection of micro-bunching and comparison with simulations are described.

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THPML070

Point Spread Function Study of Quasi-Monochromatic X-Ray Pinhole Camera at SSRF

photon, SRF, experiment, synchrotron

4803

B. Gao, H.J. Chen
SINAP, Shanghai, People's Republic of China
J. Chen, Y.B. Leng
SSRF, Shanghai, People's Republic of China

Since 2009 an X-ray pinhole camera that has been used to present the transverse beam size and emittance on diagnostic beam line of the storage ring at SSRF. The real beam size is a function of the image size of the CCD camera and point spread function (PSF) of the system. The performance of the measurement of the transverse electron beam size is given by the width of the PSF of X-ray pinhole camera. The contributions to the PSF width are the PSF of pinhole itself due to diffraction, and the PSF of the screen and camera. An X-ray monochromatic system has been established to measure the PSF accurately, and decrease the variation in the beam size between the theoretical values and the measured ones at SSRF. In this article, both calculated and measured PSF of quasi-monochromatic X-ray pinhole camera will be presented in detail.

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THPML083

Iterative Learning Control to Cancel Beam Loading Effect on Amplitude and Phase of the Accelerating Field

controls, beam-loading, cavity, feedback

4847

Z. Shahriari, K. Fong
TRIUMF, Vancouver, Canada
G. A. Dumont
UBC, Vancouver, Canada

Funding: This research is supported by TRIUMF through federal funding via a contribution agreement with the National Research Council of Canada.
Iterative learning control (ILC) is an open loop control strategy that improves the performance of a repetitive system through learning from previous iterations. ILC can be used to compensate for a repetitive disturbance like the beam loading effect in resonators. Assuming that the beam loading disturbance is identical for all iterations, the learning law can be non-causal; it can anticipate the disturbance and preemptively counteract its effect. In this work, we aim to use ILC to cancel beam loading effect on amplitude and phase. Feedback controllers are not fast enough for this purpose. A normal feed forward controller may not be sufficient as well if there is a difference between the feed forward signal and the beam loading current. Therefore, the goal is to use ILC to adaptively cancel the beam loading effect.

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THPML091

Design of a High Gradient 60 GHz Dielectric Accelerating Structure

experiment, acceleration, electromagnetic-fields, electron

4873

D.Z. Cao, D. Dan, W. Gai, C.-X. Tang, H. Zha
TUB, Beijing, People's Republic of China

RF breakdown are the main limitation for the application of high gradient structures. Higher frequencies and shorter pulse length benefit the design of accelerating structure for the breakdown threshold of surface field is E_s=f^1/2 τ^-1/4. Power source which generates very short V-band pulse with nearly hundred megawatt is now available. The paper presents the analysis of a V-band dielectric acceleration structure and power source. Future plan about RF transmission and power coupling of the whole structure will be discussed.

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THPML093

New Fast Kicker Results from the Muon g-2 E-989 Experiment at Fermilab

kicker, experiment, monitoring, MMI

4879

A.P. Schreckenberger
The University of Texas at Austin, Austin, Texas, USA
D. Barak, C.C. Jensen, G.E. Krafczyk, R.L. Madrak, H. Nguyen, H. Pfeffer, M. Popovic, J.C. Stapleton, C. Stoughton
Fermilab, Batavia, Illinois, USA
A.T. Chapelain, A.A. Mikhailichenko, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
N.S. Froemming
CENPA, Seattle, Washington, USA
J.L. Holzbauer
UMiss, University, Mississippi, USA
A.I. Keshavarzi
The University of Liverpool, Liverpool, United Kingdom

We describe the installation, commissioning, and characterization of the injection kicker system for the E-989 experiment at Fermilab for a precision measurement of the muon anomalous magnetic moment. Control and monitoring systems have been implemented to acquire and record the waveforms of each kicker pulse, and measurements of various kicker system observables were recorded in the presence of the 1.45 T g-2 storage ring magnetic field. These monitoring systems are necessary to understand the systematic contribution to the measurement of the precession frequency. We examine the dependence of muon capture to kicker field predictions.

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THPML094

New Methods for Dispersion Measurement and Correction for 12 GeV CEBAF

quadrupole, cavity, software, controls

4882

D.L. Turner
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
This paper discusses methods for dispersion measurement and correction for the Continuous Electron Beam Accelerator Facility (CEBAF) for the 12GeV era. New methods will be compared with methods used during the 6GeV era. New software tools which implement the new methods will be discussed, along with a method for automating dispersion measurement and correction. New dispersion measurement and correction methods and tools are being implemented to provide more deterministic results and to reduce machine setup time.

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THPML095

Improvement of Wire-Stretching Technique to the RF Measurements of E-Center and Multipole Field for the Dipole Cavities

cavity, kicker, coupling, electron

4885

G.-T. Park, J. Guo, H. Wang
JLab, Newport News, Virginia, USA
A. Overstreet
ODU, Norfolk, Virginia, USA
B. P. Xiao, T. Xin
BNL, Upton, Long Island, New York, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the first publication* of wire-stretching technique from its principle to measure the electrical center of a deflecting cavity, more refinements of this techniques including the review of its analytical and simulation results, RF circuit improvement to improve the signal to noise ratio and its application to other cavities have been developed. These applications include the electrical center measurements for the LHC RFD and DQW crabbing cavity prototypes, multi-frequency harmonic kicker cavity for JLEIC electron cooler**, TE011 cavity developed for the beam magnetization measurement***, and a separator cavity at BNL****. Further development of measurement calibration, error reduction, alignment of cavity installation to the machine beam line, and multipole field analysis for the beam dynamics will be presented.
*H. Wang, Proceedings of NAPAC2016, pp225-228
**S. A. Overstreet, BS Thesis 2017, Guilford College, Greensboro, NC
***J. Guo et al. these proceedings
****T. Xin et al, these proceedings

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THPML113

Design and Simulation of the Waveguide Coupler for the Cavity Beam Monitor

GUI, cavity, coupling, electromagnetic-fields

4932

Q. Wang, Q. Luo, B.G. Sun, F.F. Wu, Y.L. Yang, Z.R. Zhou
USTC/NSRL, Hefei, Anhui, People's Republic of China
Y.W. Wu
USTC, Hefei, Anhui, People's Republic of China

Funding: Supported by The National Key Research and Development Program of China (2016YFA0401900), NSFC (11375178, 11575181) and the Fundamental Research Funds for the Central Universities (WK2310000046)
The waveguide coupling is an important way to extract the signals of the specific eigenmodes required. The design of the waveguide coupler, including the waveguide-to-coaxial adapter behind it for the cavity bunch length monitor is presented. The influence of the dimension parameters is analyzed, which offers the theoretical support for the design and application of cavity bunch length monitor or cavity beam position monitor (CBPM). A series simulation based on CST is performed to verify the feasibility, and the simulation results show good performance.

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THPML126

Design of High Efficiency High Power CW Linacs for Environmental and Industrial Applications

linac, cavity, solenoid, focusing

4974

M. Shumail, V.A. Dolgashev, C.M. Markusen
SLAC, Menlo Park, California, USA

Funding: US Department of Energy, Office of High Energy Physics, through Accelerator Stewardship Grant
We have used our accelerator design toolbox equations to design three high efficiency and high power CW accelerators for the environmental and medical applications. These are: 2MeV-1MW, 10MeV-10MW, and 10MeV-1MW linacs. These are all 10 m long, 1.3 GHz, π-mode standing wave structures with design efficiencies of 96.8, 97.4 and 86.5 %, and optimal coupling coefficients of 32.9, 43.5, and 7.45, respectively. We present the detailed design parameters of these linacs. The study of single-bunch beam breakup for these linacs and the simulations results from ABCI are also included. The initial cavities are optimized according to the speed of the electron bunch to maximize the shunt impedance. The plots of peak surface fields on these cavities are also presented. We have also included a detailed thermal analysis of these linacs. Finally, we present the results of ASTRA simulations of the three linacs with magnetic focusing. We have also included the complete design of rf-distributed-coupling manifold for the third linac along with the HFSS® simulation results.

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THPML133

Design and Optimization of the Electron Gun

electron, gun, cathode, software

4995

K. Huang, T.L. He, Z.L. Ren, D.R. Xu, H. Xu
USTC/NSRL, Hefei, Anhui, People's Republic of China
Y. Chen
Department of Information Engineering , Anhui Economic Management Cadres' Institute, Hefei, Anhui, People's Republic of China

Funding: Work supported by the National Nature Science Foundation of China under Grant Nos.11375176 and 10875118.
Design of an energy-modified electron gun is of significance to do some research on the properties of Diamond-amplified cathode. Based on the design method of the Pierce electron gun, the optimum parameters of the electron gun have been obtained using the Opera-3D program. And the beam waist's position, the beam current, the beam size and the beam emittance related to the electron bean energy was investigated in this paper.

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THPML136

Study of Secondary Electron Generation and Transport in Diamond

electron, scattering, cathode, database

5004

T.L. He, K. Huang, Z.L. Ren, L. Wang, D.R. Xu, H. Xu
USTC/NSRL, Hefei, Anhui, People's Republic of China

Energetic primary electrons (~ keV) impinging on the diamond film with its both surface under bias field in ~ MV/m, will excite secondary electron (SE) response including SE generation & transport. Although there have been 3D Monte Carlo (MC) simulation to study the two processes, this paper will introduce another method. Based on optical dielectric model, 3D MC simulation was implemented to study the generation process, and SE generation function was obtained by fitting the calculations. Using this function, the diffusion-drift equation of charge carriers (electron and hole) can be solved in 1D for the transport process, and the variation of SE depth distribution with time can be obtained.

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THPML138

Efficiency and Error Analysis of the HALS Injection Scheme

injection, kicker, lattice, storage-ring

5008

Z.B. Sun, G. Liu, W. Liu, F.L. Shang, L. Shang, W.B. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

Hefei Advanced Light Source (HALS) is a newly designed diffraction-limited storage ring.. The latest version of HALS has a 7BA lattice. One of the most important parts about HALS design is its injection system. Since conventional injection scheme is not suitable for DLSRs, many new injection schemes are proposed, including longitudinal injection scheme. In this paper, we investigate the feasibility of longitudinal injection scheme for HALS. In order to evaluate the injection performance, various errors have been considered. A series of tracking simulations are carried out and injection efficiency is obtained under different error levels.

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FRXGBD2

Fast Kicker for High Current Beam Manipulation: Experimental Facility

kicker, experiment, septum, electron

5019

V.V. Gambaryan, A.A. Starostenko
BINP SB RAS, Novosibirsk, Russia
A.A. Starostenko
NSU, Novosibirsk, Russia

The pulsed deflecting magnet (kicker) project was worked out in Budker Institute of Nuclear Physics. The kicker design parameters are: impulsive force, 1 mT*m; pulse edge, 5 ns; impulse duration, 200 ns. The unconventional approach is that the plates must be replaced by a set of cylinders. The obtained magnet construction enables the field homogeneity to be controlled by changing current magnitudes in cylinders. Furthermore, we demonstrated the method of field optimization. In addition, measurement technique for the harmonic components was considered and the possibility of control harmonic components value was demonstrated. The results with electron beam on actual facility was considered.

Slides FRXGBD2 [4.864 MB]

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