IPAC2018 - List of Keywords (focusing)

Paper	Title	Other Keywords	Page
TUXGBE3	Status of Plasma-Based Experiments at the SPARC_LAB Test Facility	plasma, electron, experiment, emittance	603
	E. Chiadroni, D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, F.G. Bisesto, E. Brentegani, F. Cardelli, G. Costa, M. Croia, D. Di Giovenale, G. Di Pirro, M. Ferrario, F. Filippi, A. Gallo, A. Giribono, A. Marocchino, L. Piersanti, R. Pompili, S. Romeo, J. Scifo, V. Shpakov, A. Stella, C. Vaccarezza, F. Villa INFN/LNF, Frascati (Roma), Italy A. Cianchi INFN-Roma II, Roma, Italy M. Marongiu, A. Mostacci Sapienza University of Rome, Rome, Italy J.B. Rosenzweig UCLA, Los Angeles, California, USA A.R. Rossi Istituto Nazionale di Fisica Nucleare, Milano, Italy A. Zigler The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel
	The current activity of the SPARC LAB test-facility is focused on the realization of plasma-based acceleration experiments with the aim to provide accelerating field of the order of several GV/m while maintaining the overall quality (in terms of energy spread and emittance) of the accelerated electron bunch. The current status of such an activity is presented, together with results related to the applicability of plasmas as focusing lenses in view of a complete plasma-based focusing, accelerating and extraction system.
	Slides TUXGBE3 [10.258 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUXGBE3
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TUPAL042	On Possibility of Reflective Triode Uses for Thermonuclear Neutron Generation in Budker-Post Trap with Pulsed Magnetic Field	plasma, neutron, proton, electron	1100
	V.I. Rashchikov, A.N. Didenko, A.A. Isaev, K.I. Kozlovskiy, V.L. Shatokhin, A.E. Shikanov, E.D. Vovchenko MEPhI, Moscow, Russia
	Scheme for thermonuclear neutron generation in compact Budker-Post trap with barrel-shaped pulsed magnetic field produced by two symmetrically located thin coils with diameter not exceed 0.05 m is proposed. During neutron generation in the trap simultaneously forms plasma which include hydrogen nuclides with density up to 10¹³ m-3 and two pulsed counter hydrogen nuclides flows accelerated in the diodes. Diodes consist of transparent anode with the form of sphere sector symmetrically covered by the same form grounded cathode. Diodes located symmetrically in front of each other, coaxially to magnetic trap. Computer simulation shows possibility to generate up to 1010 neutrons per pulse for deuterium-tritium compound in the diode system with transverse dimension ~0.1 m, amplitude and accelerating pulse duration 5.105 V and 100 nsec. The value of magnetic induction in the center of the trap should be approximately equal to 20 T.
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TUPMF024	Validation of the Halbach FFAG Cell of Cornell-BNL Energy Recovery Linac	linac, permanent-magnet, quadrupole, collider	1304
	F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas 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. The optical properties of the Halbach technology based CBETA ERL return FFAG arc cell are investigated, using its 3-D OPERA field map model. This includes paraxial and large amplitude motion, tune path, study of resonances, dynamic acceptance, effects of various defects, 300-cell 10k-particle bunches 6D transmission trials. These investigations, a 2~3 year investment, have validated the Halbach technology in the linear FFAG cell application, from the point of view of the beam dynamics, so supporting its approval as the required technology for CBETA, in December 2016.
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TUPML022	Assessment of Transverse Instabilities in Proton Driven Hollow Plasma Wakefield Acceleration	plasma, proton, electron, wakefield	1581
	Y. M. Li, G.X. Xia, Y. Zhao UMAN, Manchester, United Kingdom S.J. Gessner CERN, Geneva, Switzerland
	Hollow plasma has been introduced into the proton-driven plasma wakefield accelerators to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and time in uniform plasma. It has been demonstrated in simulations that the electrons can be accelerated to energy frontier with well-preserved beam quality in a long hollow plasma channel. However, this scheme imposes tight requirements on the beam-channel alignment. Otherwise asymmetric transverse wakefields along the axis are induced, which could distort the driving bunch and deteriorate the witness beam quality. In this paper, by means of the 2D cartesian particle-in-cell simulations, we examine the potentially detrimental effects induced by the driving beam-channel offset and initial driver tilt, and then propose and assess the solutions to these driver inaccuracy issues.
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TUPML023	Amplitude Enhancement of the Self-Modulated Plasma Wakefields	proton, plasma, wakefield, ECR	1585
	Y. M. Li, G.X. Xia, Y. Zhao UMAN, Manchester, United Kingdom K.V. Lotov, A. Sosedkin Budker INP & NSU, Novosibirsk, Russia
	Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML023
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TUPML038	Simulation of Phase-Dependent Transverse Focusing in Dielectric Laser Accelerator Based Lattices	lattice, laser, emittance, quadrupole	1622
	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 The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation aims to demonstrate a prototype of a fully integrated accelerator on a microchip based on laser-driven dielectric structures until 2021. Such an accelerator on a chip needs all components known from classical accelerators. This includes an electron source, accelerating structures and transverse focusing arrangements. Since the period of the accelerating field is connected to the drive laser wavelength of typically a few microns, not only longitudinal but also transverse effects are strongly phase-dependent even for few femtosecond long bunches. If both the accelerating and focusing elements are DLA-based, this needs to be taken into account. In this work we study in detail the implications of a phase-dependent focusing lattice on the evolution of the transverse phase space of a transported bunch.
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TUPML046	Characterization of Self-Modulated Electron Bunches in an Argon Plasma	plasma, electron, experiment, solenoid	1645
	M. Groß, P. Boonpornprasert, Y. Chen, J. Engel, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, R. Niemczyk, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao DESY Zeuthen, Zeuthen, Germany R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff DESY, Hamburg, Germany F.J. Grüner CFEL, Hamburg, Germany F.J. Grüner, A. Martinez de la Ossa University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany T.J. Mehrling, C.B. Schroeder LBNL, Berkeley, USA I. Will MBI, Berlin, Germany
	The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect* the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 10¹³ cm^-3 to 1015 cm^-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing. * M. Gross et al., "Observation of the self-modulation instabil-ity via time-resolved measurements", accepted for publication at Phys. Rev. Lett.
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WEPAK003	Effect of Model Errors on the Closed Orbit Correction at the SIS18 Synchrotron of GSI	quadrupole, synchrotron, closed-orbit, controls	2080
	S.H. Mirza, P. Forck, H. Klingbeil, R. Singh GSI, Darmstadt, Germany H. Klingbeil TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Deutscher Akademischer Austauschdienst under contract No. 91605207 A fast closed orbit feedback system (bandwidth in the order of 1 kHz) is under development at the GSI SIS18 synchrotron for the orbit correction from injection to extraction including the acceleration ramp. The static process model, represented as the orbit response matrix (ORM), is subjected to the systematic optics changes during ramp e.g. beta function and phase advance variations at the locations of BPMs and steerers. In addition to these systematic variations, model mismatches may arise from dipole and quadrupole magnet errors, space charge dependent tune shift as well as BPM and steerer calibration errors. In this contribution, the effects of these model errors on the closed orbit correction are investigated which is necessary for the robust stability analysis of the feedback controller. For the robustness tests, the traditional SVD-based matrix pseudo-inversion is compared to a Fourier-based analysis. The results are achieved by detailed simulations in MADX.
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WEPAL045	An Electrostatic Fixed-Slit Emittance Measurement System	emittance, cathode, electron, FEL	2274
	J.W. Lewellen, H.L. Andrews, R.L. Fleming, K.E. Nichols, E.I. Simakov LANL, Los Alamos, New Mexico, USA
	Funding: Los Alamos National Laboratory LDRD Program The emittance of a field emission cathode can be difficult to measure close to the emitter, due to the high average current density of the beam and the potential for desorbed material from an imaging screen to contaminate the cathode. We present the design for a dual fixed-slit emittance measurement system for a field emitter cathode, implemented using electrostatic deflecting plates. Results from fabrication and initial testing will be presented.
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WEPMF061	High Gradient Pulsed Quadrupoles for Novel Accelerators and Space Charge Limited Beam Transport	plasma, quadrupole, electron, wakefield	2505
	C. Tenholt CERN, Geneva, Switzerland G. Loisch, F. Stephan DESY Zeuthen, Zeuthen, Germany B. Marchetti DESY, Hamburg, Germany
	Novel acceleration schemes like plasma wake-field based accelerators demand for high gradient focusing elements to match the Twiss parameters in the plasma to the transport lattice of the conventional accelerator beamlines, with typically much higher beta-functions. There are multiple candidates for achieving high gradient focusing fields, each one having certain drawbacks. Permanent magnets are limited in tunability, plasma lenses might degrade the transverse beam quality significantly and conventional magnets cannot reach very high gradients and often cannot be placed in direct proximity of the plasma accelerator because of their size. In this paper we present design considerations and simulations on compact, high gradient, pulsed quadrupoles, that could be used e.g. for final focusing of space charge dominated bunches into a LWFA (Laser Wake-Field Accelerator) at SINBAD or other facilities with similar demands. The target design gradient is 200 T/m at a physical aperture on the order of 10 mm.
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THYGBF2	PIP-II Injector Test Warm Front End: Commissioning Update	kicker, rfq, operation, emittance	2943
	L.R. Prost, R. Andrews, C.M. Baffes, J.-P. Carneiro, B.E. Chase, A.Z. Chen, E. Cullerton, P. Derwent, J.P. Edelen, J. Einstein-Curtis, D. Frolov, B.M. Hanna, D.W. Peterson, G.W. Saewert, A. Saini, V.E. Scarpine, A.V. Shemyakin, V.L. Sista, J. Steimel, D. Sun, A. Warner Fermilab, Batavia, Illinois, USA C.J. Richard NSCL, East Lansing, Michigan, USA V.L. Sista BARC, Mumbai, India
	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 Warm Front End (WFE) of the Proton Improvement Plan II Injector Test [1] at Fermilab has been constructed to its full length. It includes a 15-mA DC, 30-keV H⁻ ion source, a 2 m-long Low Energy Beam Transport (LEBT) with a switching dipole magnet, a 2.1 MeV CW RFQ, followed by a Medium Energy Beam Transport (MEBT) with various diagnostics and a dump. This report presents the commissioning status, focusing on beam measurements in the MEBT. In particular, a beam with the parameters required for injection into the Booster (5 mA, 0.55 ms macro-pulse at 20 Hz) was transported through the WFE.
	Slides THYGBF2 [2.434 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THYGBF2
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THPAF023	The Beam Optics of the FFAG Cell of the CBETA ERL Accelerator	optics, quadrupole, linac, electron	3000
	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. The Cornell-Brookhaven Energy Recovery Linac Test Accelerator now under construction will accelerate electrons from 6 MeV to 150 MeV in four linac passes, using a single return line accepting all energies from 42 to 150 MeV. We describe the optical design of the machine, with emphasis on recent updates. We explain how we choose parameters for the wide energy acceptance return arc, taking into account 3D field maps generated from magnet designs. We give the final machine parameters resulting from iterations between desired lattice properties and magnet design. We modified the optics to improve the periodicity of the return arc near its ends and to create adequate space for vacuum hardware. The return arc is connected to the linac with splitter lines that serve to match the optics for each beam energy. We describe how matching conditions were chosen for the splitter lines and how we use them to control longitudinal motion. We simulate the injection and low energy extraction systems including space charge effects, matching the beam properties to the optical parameters of the rest of the machine.
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THPAF070	Design of a One-Dimensional Sextupole Using Semi-Analytic Methods	sextupole, lattice, quadrupole, coupling	3140
	L. Gupta Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA S. Baturin Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA Y.K. Kim University of Chicago, Chicago, Illinois, USA S. Nagaitsev Fermilab, Batavia, Illinois, USA
	Funding: Work supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams Sextupole magnets provide position-dependent momentum kicks and are tuned to provide the correct kicks to particles within a small acceptance region in phase space. Sextupoles are useful and even necessary in circular accelerators for chromaticity corrections. They are routinely used in most rings, i.e. CESR. Although sextupole magnets are necessary for particle energy corrections, they also have undesirable effects on dynamic aperture, especially because of their non-linear coupling term in the momentum kick. Studies of integrable systems suggest that there is an analytic way to create transport lattices with specific transfer matrices that limit the momentum kick to one dimension. A one-dimension sextupole is needed for chromaticity corrections: a horizontal sextupole for horizontal bending magnets. We know how to make a "composite" horizontal sextupole using regular 2D sextupoles and linear transfer matrices in an ideal thin-lens approximation. Thus, one could create an accelerator lattice using linear elements, in series with sextupole magnets to create a '1d sextupole'. This paper describes progress towards realizing a realistic focusing lattice resulting in a 1d sextupole.* *S.A. Antipov, et. al., Single-particle dynamics in a nonlinear accelerator lattice: attaining a large tune spread with octupoles in IOTA, Journal of Instrumentation, Volume 12, April 2017.
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THPAK040	Bunched Beam Envelope Instability in a Periodic Focusing Channel	emittance, simulation, 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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THPAK094	High Acceptance Beamline for the Capture of a Laser Wakefield Accelerated Beam	quadrupole, plasma, permanent-magnet, laser	3456
	B.D. Muratori, J.K. Jones STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom K.A. Dewhurst University of Manchester, Manchester, United Kingdom K.A. Dewhurst, J.K. Jones, H.L. Owen Cockcroft Institute, Warrington, Cheshire, United Kingdom H.L. Owen UMAN, Manchester, United Kingdom
	Laser wakefield acceleration, together with other types of novel acceleration techniques, has seen considerable progress of late. Together with this progress comes a question, which has only recently started to be addressed, of how to transport and utilise such beams. This is a challenge because of the high initial divergence of these beams. There are several approaches to this problem and we concentrate on one in this paper and look at the implications of it in some detail.
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THPAK097	Ion Optic Design of the Microprobe System at Sichuan University	brightness, target, proton, quadrupole	3460
	Z. Li, Z. An, J.F. Han, G.Q. Zheng SCU, Chengdu, People's Republic of China
	Funding: Supported by the National Natural Science Foundation of China (11375122, 11511140277) At the end of 2016, the first beam was extracted from the 3.0 MV Tandetron accelerator system at Sichuan University, China. The accelerator is imported from the HVEE as a multi-purpose research platform. For one of the main applications, the system will be connected to a micro-beamline to achieve submicron resolution, so the accelerator is designed with energy stability as high as 0.01%. The measured brightness for 3 MeV proton beam is 5.06 pA/um2mrad2MeV and the energy stability is reached the goal of design. The ion optic design of the microprobe beam line will be presented in this paper.
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THPAK109	Improved Simulation for Centre Region of TRIUMF 500 MeV Cyclotron with Space Charge	space-charge, TRIUMF, simulation, 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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THPAK118	Beam Dynamics Studies for a Strong-Focusing Cyclotron	cavity, dipole, cyclotron, betatron	3522
	J. Gerity, S. Assadi, P.M. McIntyre, A. Sattarov Texas A&M University, College Station, USA
	Results are presented from end-to-end simulation of a 100 MeV strong focusing cyclotron (SFC). The develop-ment of the high-current SFC is motivated by applica-tions for production of medical isotopes and for a proton driver for subcritical fission. It uses a novel superconducting cavity to provide suffi-cient energy gain to fully separate all turns. An arc-contour F-D doublet, trim dipole winding, and sextupole are located along each turn within the aperture of each sector dipole to control the betatron and synchrotron motion and to stabilize non-linear dynamics with high-current operation. The phase space evolution of a proton bunch in the SFC was simulated using both the code OPAL and an ad hoc Runge-Kutta tracker. Iterative optimization of the dipole, quadrupole, and sextupole fields was used to provide precise isochronicity, favorable betatron phase advance, and cancellation of dispersion in each cell.
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THPAL024	A Simple Variable Focus Lens for Field Emitter Cathodes	cathode, emittance, laser, simulation	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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THPMF077	A Novel 7BA Lattice for a 196-m Circumference Diffraction-Limited Soft X-Ray Storage Ring	lattice, emittance, optics, sextupole	4252
	S.C. Leemann, W.E. Byrne, M. Venturini LBNL, Berkeley, California, USA J. Bengtsson DLS, Oxfordshire, United Kingdom A. Streun PSI, Villigen PSI, Switzerland
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231 The current baseline for the ALS Upgrade to a diffraction-limited soft x-ray storage ring is a 9BA lattice with two dispersion bumps for localized chromatic corrections. Although this lattice meets the very aggressive emittance goal, it offers limited margins in terms of dynamic aperture and momentum acceptance. In this paper we explore a different approach based on a 7BA lattice with distributed chromatic correction. This lattice relies heavily on longitudinal gradient bends and reverse bending in order to suppress the emittance so that despite fewer bends an emittance comparable to the baseline lattice can be reached albeit with larger dynamic aperture and momentum acceptance. We present linear optics design, trade-offs between achievable emittance and longitudinal stability, as well as the employed nonlinear tuning approach and the resulting performance of this alternate lattice.
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THPMK082	Micro Bunch Rotation and Coherent Undulator Radiation From a Kicked Beam	undulator, quadrupole, electron, radiation	4489
	J.P. MacArthur Stanford University, Stanford, California, USA Z. Huang, J. Krzywinski, A.A. Lutman SLAC, Menlo Park, California, USA
	Recent observations of x-rays from a microbunched beam that has been kicked off-axis have shown coherent radiation at surprisingly large angles, in some cases reaching 30-50 uRad. Previous work on the topic has suggested that radiation at such large angles is inconsistent with classical radiation theory because microbunches cannot tilt. Here we show that, when kicked in a quadrupole lattice, microbunches can automatically tilt toward a new direction of propagation. This allows for coherent radiation farther off axis.
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THPML018	Modeling of Self-Modulated Laser Wakefield Acceleration Driven by Sub-Terawatt Laser Pulses	laser, electron, plasma, target	4690
	C.-Y. Hsieh, S.-H. Chen NCU, Chung Li, Taiwan M.W. Lin National Tsing-Hua University (NTHU), Hsinchu, Taiwan
	Funding: This work has been supported by the Ministry of Science and Technology in Taiwan by grant MOST104-2112-M-008-013-MY3 and by grant MOST105-2112-M-007-036-MY3. Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly. A. J. Goers et al., Phys. Rev. Lett. 115, 194802 (2015). ** E. Kaksis et al., Opt. Express 24, 25, 28915 (2016).
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THPML106	Electron Microscopy Inspired Setup for Single-Shot 4-D Trace Space Reconstruction of Bright Electron Beams	emittance, electron, detector, experiment	4909
	J. Giner Navarro, D.B. Cesar, P. Musumeci UCLA, Los Angeles, California, USA R.W. Aßmann, B. Marchetti, D. Marx DESY, Hamburg, Germany
	Funding: This work has been partially supported by the National Science Foundation under Grant No. 1549132 and Department of Energy under award No. DE-SC0009914. In the development of low charge, single-shot diagnostics for high brightness electron beams, Transmission Electron Microscopy (TEM) grids present certain advantages compared to pepper pot masks due to higher beam transmission. In this paper, we developed a set of criteria to optimize the resolution of a point projection image. However, this configuration of the beam with respect to the grid and detector positions implies the measurement of a strongly correlated phase space which entails a large sensitivity to small measurement errors in retrieving the projected emittance. We discuss the possibility of an alternative scheme by inserting a magnetic focusing system in between the grid and the detector, similar to an electron microscope design, to reconstruct the phase space when the beam is focused on the grid.
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THPML126	Design of High Efficiency High Power CW Linacs for Environmental and Industrial Applications	linac, cavity, simulation, solenoid	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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Paper

Title

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Page

TUXGBE3

Status of Plasma-Based Experiments at the SPARC_LAB Test Facility

plasma, electron, experiment, emittance

603

E. Chiadroni, D. Alesini, M.P. Anania, M. Bellaveglia, A. Biagioni, F.G. Bisesto, E. Brentegani, F. Cardelli, G. Costa, M. Croia, D. Di Giovenale, G. Di Pirro, M. Ferrario, F. Filippi, A. Gallo, A. Giribono, A. Marocchino, L. Piersanti, R. Pompili, S. Romeo, J. Scifo, V. Shpakov, A. Stella, C. Vaccarezza, F. Villa
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
INFN-Roma II, Roma, Italy
M. Marongiu, A. Mostacci
Sapienza University of Rome, Rome, Italy
J.B. Rosenzweig
UCLA, Los Angeles, California, USA
A.R. Rossi
Istituto Nazionale di Fisica Nucleare, Milano, Italy
A. Zigler
The Hebrew University of Jerusalem, The Racah Institute of Physics, Jerusalem, Israel

The current activity of the SPARC LAB test-facility is focused on the realization of plasma-based acceleration experiments with the aim to provide accelerating field of the order of several GV/m while maintaining the overall quality (in terms of energy spread and emittance) of the accelerated electron bunch. The current status of such an activity is presented, together with results related to the applicability of plasmas as focusing lenses in view of a complete plasma-based focusing, accelerating and extraction system.

Slides TUXGBE3 [10.258 MB]

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TUPAL042

On Possibility of Reflective Triode Uses for Thermonuclear Neutron Generation in Budker-Post Trap with Pulsed Magnetic Field

plasma, neutron, proton, electron

1100

V.I. Rashchikov, A.N. Didenko, A.A. Isaev, K.I. Kozlovskiy, V.L. Shatokhin, A.E. Shikanov, E.D. Vovchenko
MEPhI, Moscow, Russia

Scheme for thermonuclear neutron generation in compact Budker-Post trap with barrel-shaped pulsed magnetic field produced by two symmetrically located thin coils with diameter not exceed 0.05 m is proposed. During neutron generation in the trap simultaneously forms plasma which include hydrogen nuclides with density up to 10¹³ m-3 and two pulsed counter hydrogen nuclides flows accelerated in the diodes. Diodes consist of transparent anode with the form of sphere sector symmetrically covered by the same form grounded cathode. Diodes located symmetrically in front of each other, coaxially to magnetic trap. Computer simulation shows possibility to generate up to 1010 neutrons per pulse for deuterium-tritium compound in the diode system with transverse dimension ~0.1 m, amplitude and accelerating pulse duration 5.105 V and 100 nsec. The value of magnetic induction in the center of the trap should be approximately equal to 20 T.

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TUPMF024

Validation of the Halbach FFAG Cell of Cornell-BNL Energy Recovery Linac

linac, permanent-magnet, quadrupole, collider

1304

F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas
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.
The optical properties of the Halbach technology based CBETA ERL return FFAG arc cell are investigated, using its 3-D OPERA field map model. This includes paraxial and large amplitude motion, tune path, study of resonances, dynamic acceptance, effects of various defects, 300-cell 10k-particle bunches 6D transmission trials. These investigations, a 2~3 year investment, have validated the Halbach technology in the linear FFAG cell application, from the point of view of the beam dynamics, so supporting its approval as the required technology for CBETA, in December 2016.

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TUPML022

Assessment of Transverse Instabilities in Proton Driven Hollow Plasma Wakefield Acceleration

plasma, proton, electron, wakefield

1581

Y. M. Li, G.X. Xia, Y. Zhao
UMAN, Manchester, United Kingdom
S.J. Gessner
CERN, Geneva, Switzerland

Hollow plasma has been introduced into the proton-driven plasma wakefield accelerators to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and time in uniform plasma. It has been demonstrated in simulations that the electrons can be accelerated to energy frontier with well-preserved beam quality in a long hollow plasma channel. However, this scheme imposes tight requirements on the beam-channel alignment. Otherwise asymmetric transverse wakefields along the axis are induced, which could distort the driving bunch and deteriorate the witness beam quality. In this paper, by means of the 2D cartesian particle-in-cell simulations, we examine the potentially detrimental effects induced by the driving beam-channel offset and initial driver tilt, and then propose and assess the solutions to these driver inaccuracy issues.

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TUPML023

Amplitude Enhancement of the Self-Modulated Plasma Wakefields

proton, plasma, wakefield, ECR

1585

Y. M. Li, G.X. Xia, Y. Zhao
UMAN, Manchester, United Kingdom
K.V. Lotov, A. Sosedkin
Budker INP & NSU, Novosibirsk, Russia

Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed.

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TUPML038

Simulation of Phase-Dependent Transverse Focusing in Dielectric Laser Accelerator Based Lattices

lattice, laser, emittance, quadrupole

1622

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
The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation aims to demonstrate a prototype of a fully integrated accelerator on a microchip based on laser-driven dielectric structures until 2021. Such an accelerator on a chip needs all components known from classical accelerators. This includes an electron source, accelerating structures and transverse focusing arrangements. Since the period of the accelerating field is connected to the drive laser wavelength of typically a few microns, not only longitudinal but also transverse effects are strongly phase-dependent even for few femtosecond long bunches. If both the accelerating and focusing elements are DLA-based, this needs to be taken into account. In this work we study in detail the implications of a phase-dependent focusing lattice on the evolution of the transverse phase space of a transported bunch.

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TUPML046

Characterization of Self-Modulated Electron Bunches in an Argon Plasma

plasma, electron, experiment, solenoid

1645

M. Groß, P. Boonpornprasert, Y. Chen, J. Engel, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, R. Niemczyk, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao
DESY Zeuthen, Zeuthen, Germany
R. Brinkmann, A. Martinez de la Ossa, J. Osterhoff
DESY, Hamburg, Germany
F.J. Grüner
CFEL, Hamburg, Germany
F.J. Grüner, A. Martinez de la Ossa
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
T.J. Mehrling, C.B. Schroeder
LBNL, Berkeley, USA
I. Will
MBI, Berlin, Germany

The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect* the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 10¹³ cm^-3 to 1015 cm^-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing.
* M. Gross et al., "Observation of the self-modulation instabil-ity via time-resolved measurements", accepted for publication at Phys. Rev. Lett.

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WEPAK003

Effect of Model Errors on the Closed Orbit Correction at the SIS18 Synchrotron of GSI

quadrupole, synchrotron, closed-orbit, controls

2080

S.H. Mirza, P. Forck, H. Klingbeil, R. Singh
GSI, Darmstadt, Germany
H. Klingbeil
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Deutscher Akademischer Austauschdienst under contract No. 91605207
A fast closed orbit feedback system (bandwidth in the order of 1 kHz) is under development at the GSI SIS18 synchrotron for the orbit correction from injection to extraction including the acceleration ramp. The static process model, represented as the orbit response matrix (ORM), is subjected to the systematic optics changes during ramp e.g. beta function and phase advance variations at the locations of BPMs and steerers. In addition to these systematic variations, model mismatches may arise from dipole and quadrupole magnet errors, space charge dependent tune shift as well as BPM and steerer calibration errors. In this contribution, the effects of these model errors on the closed orbit correction are investigated which is necessary for the robust stability analysis of the feedback controller. For the robustness tests, the traditional SVD-based matrix pseudo-inversion is compared to a Fourier-based analysis. The results are achieved by detailed simulations in MADX.

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WEPAL045

An Electrostatic Fixed-Slit Emittance Measurement System

emittance, cathode, electron, FEL

2274

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

Funding: Los Alamos National Laboratory LDRD Program
The emittance of a field emission cathode can be difficult to measure close to the emitter, due to the high average current density of the beam and the potential for desorbed material from an imaging screen to contaminate the cathode. We present the design for a dual fixed-slit emittance measurement system for a field emitter cathode, implemented using electrostatic deflecting plates. Results from fabrication and initial testing will be presented.

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WEPMF061

High Gradient Pulsed Quadrupoles for Novel Accelerators and Space Charge Limited Beam Transport

plasma, quadrupole, electron, wakefield

2505

C. Tenholt
CERN, Geneva, Switzerland
G. Loisch, F. Stephan
DESY Zeuthen, Zeuthen, Germany
B. Marchetti
DESY, Hamburg, Germany

Novel acceleration schemes like plasma wake-field based accelerators demand for high gradient focusing elements to match the Twiss parameters in the plasma to the transport lattice of the conventional accelerator beamlines, with typically much higher beta-functions. There are multiple candidates for achieving high gradient focusing fields, each one having certain drawbacks. Permanent magnets are limited in tunability, plasma lenses might degrade the transverse beam quality significantly and conventional magnets cannot reach very high gradients and often cannot be placed in direct proximity of the plasma accelerator because of their size. In this paper we present design considerations and simulations on compact, high gradient, pulsed quadrupoles, that could be used e.g. for final focusing of space charge dominated bunches into a LWFA (Laser Wake-Field Accelerator) at SINBAD or other facilities with similar demands. The target design gradient is 200 T/m at a physical aperture on the order of 10 mm.

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THYGBF2

PIP-II Injector Test Warm Front End: Commissioning Update

kicker, rfq, operation, emittance

2943

L.R. Prost, R. Andrews, C.M. Baffes, J.-P. Carneiro, B.E. Chase, A.Z. Chen, E. Cullerton, P. Derwent, J.P. Edelen, J. Einstein-Curtis, D. Frolov, B.M. Hanna, D.W. Peterson, G.W. Saewert, A. Saini, V.E. Scarpine, A.V. Shemyakin, V.L. Sista, J. Steimel, D. Sun, A. Warner
Fermilab, Batavia, Illinois, USA
C.J. Richard
NSCL, East Lansing, Michigan, USA
V.L. Sista
BARC, Mumbai, India

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 Warm Front End (WFE) of the Proton Improvement Plan II Injector Test [1] at Fermilab has been constructed to its full length. It includes a 15-mA DC, 30-keV H⁻ ion source, a 2 m-long Low Energy Beam Transport (LEBT) with a switching dipole magnet, a 2.1 MeV CW RFQ, followed by a Medium Energy Beam Transport (MEBT) with various diagnostics and a dump. This report presents the commissioning status, focusing on beam measurements in the MEBT. In particular, a beam with the parameters required for injection into the Booster (5 mA, 0.55 ms macro-pulse at 20 Hz) was transported through the WFE.

Slides THYGBF2 [2.434 MB]

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THPAF023

The Beam Optics of the FFAG Cell of the CBETA ERL Accelerator

optics, quadrupole, linac, electron

3000

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.
The Cornell-Brookhaven Energy Recovery Linac Test Accelerator now under construction will accelerate electrons from 6 MeV to 150 MeV in four linac passes, using a single return line accepting all energies from 42 to 150 MeV. We describe the optical design of the machine, with emphasis on recent updates. We explain how we choose parameters for the wide energy acceptance return arc, taking into account 3D field maps generated from magnet designs. We give the final machine parameters resulting from iterations between desired lattice properties and magnet design. We modified the optics to improve the periodicity of the return arc near its ends and to create adequate space for vacuum hardware. The return arc is connected to the linac with splitter lines that serve to match the optics for each beam energy. We describe how matching conditions were chosen for the splitter lines and how we use them to control longitudinal motion. We simulate the injection and low energy extraction systems including space charge effects, matching the beam properties to the optical parameters of the rest of the machine.

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THPAF070

Design of a One-Dimensional Sextupole Using Semi-Analytic Methods

sextupole, lattice, quadrupole, coupling

3140

L. Gupta
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
S. Baturin
Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
Y.K. Kim
University of Chicago, Chicago, Illinois, USA
S. Nagaitsev
Fermilab, Batavia, Illinois, USA

Funding: Work supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams
Sextupole magnets provide position-dependent momentum kicks and are tuned to provide the correct kicks to particles within a small acceptance region in phase space. Sextupoles are useful and even necessary in circular accelerators for chromaticity corrections. They are routinely used in most rings, i.e. CESR. Although sextupole magnets are necessary for particle energy corrections, they also have undesirable effects on dynamic aperture, especially because of their non-linear coupling term in the momentum kick. Studies of integrable systems suggest that there is an analytic way to create transport lattices with specific transfer matrices that limit the momentum kick to one dimension. A one-dimension sextupole is needed for chromaticity corrections: a horizontal sextupole for horizontal bending magnets. We know how to make a "composite" horizontal sextupole using regular 2D sextupoles and linear transfer matrices in an ideal thin-lens approximation. Thus, one could create an accelerator lattice using linear elements, in series with sextupole magnets to create a '1d sextupole'. This paper describes progress towards realizing a realistic focusing lattice resulting in a 1d sextupole.*
*S.A. Antipov, et. al., Single-particle dynamics in a nonlinear accelerator lattice: attaining a large tune spread with octupoles in IOTA, Journal of Instrumentation, Volume 12, April 2017.

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THPAK040

Bunched Beam Envelope Instability in a Periodic Focusing Channel

emittance, simulation, 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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THPAK094

High Acceptance Beamline for the Capture of a Laser Wakefield Accelerated Beam

quadrupole, plasma, permanent-magnet, laser

3456

B.D. Muratori, J.K. Jones
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
K.A. Dewhurst
University of Manchester, Manchester, United Kingdom
K.A. Dewhurst, J.K. Jones, H.L. Owen
Cockcroft Institute, Warrington, Cheshire, United Kingdom
H.L. Owen
UMAN, Manchester, United Kingdom

Laser wakefield acceleration, together with other types of novel acceleration techniques, has seen considerable progress of late. Together with this progress comes a question, which has only recently started to be addressed, of how to transport and utilise such beams. This is a challenge because of the high initial divergence of these beams. There are several approaches to this problem and we concentrate on one in this paper and look at the implications of it in some detail.

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THPAK097

Ion Optic Design of the Microprobe System at Sichuan University

brightness, target, proton, quadrupole

3460

Z. Li, Z. An, J.F. Han, G.Q. Zheng
SCU, Chengdu, People's Republic of China

Funding: Supported by the National Natural Science Foundation of China (11375122, 11511140277)
At the end of 2016, the first beam was extracted from the 3.0 MV Tandetron accelerator system at Sichuan University, China. The accelerator is imported from the HVEE as a multi-purpose research platform. For one of the main applications, the system will be connected to a micro-beamline to achieve submicron resolution, so the accelerator is designed with energy stability as high as 0.01%. The measured brightness for 3 MeV proton beam is 5.06 pA/um2mrad2MeV and the energy stability is reached the goal of design. The ion optic design of the microprobe beam line will be presented in this paper.

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THPAK109

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

space-charge, TRIUMF, simulation, 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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THPAK118

Beam Dynamics Studies for a Strong-Focusing Cyclotron

cavity, dipole, cyclotron, betatron

3522

J. Gerity, S. Assadi, P.M. McIntyre, A. Sattarov
Texas A&M University, College Station, USA

Results are presented from end-to-end simulation of a 100 MeV strong focusing cyclotron (SFC). The develop-ment of the high-current SFC is motivated by applica-tions for production of medical isotopes and for a proton driver for subcritical fission. It uses a novel superconducting cavity to provide suffi-cient energy gain to fully separate all turns. An arc-contour F-D doublet, trim dipole winding, and sextupole are located along each turn within the aperture of each sector dipole to control the betatron and synchrotron motion and to stabilize non-linear dynamics with high-current operation. The phase space evolution of a proton bunch in the SFC was simulated using both the code OPAL and an ad hoc Runge-Kutta tracker. Iterative optimization of the dipole, quadrupole, and sextupole fields was used to provide precise isochronicity, favorable betatron phase advance, and cancellation of dispersion in each cell.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK118

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THPAL024

A Simple Variable Focus Lens for Field Emitter Cathodes

cathode, emittance, laser, simulation

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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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAL024

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THPMF077

A Novel 7BA Lattice for a 196-m Circumference Diffraction-Limited Soft X-Ray Storage Ring

lattice, emittance, optics, sextupole

4252

S.C. Leemann, W.E. Byrne, M. Venturini
LBNL, Berkeley, California, USA
J. Bengtsson
DLS, Oxfordshire, United Kingdom
A. Streun
PSI, Villigen PSI, Switzerland

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231
The current baseline for the ALS Upgrade to a diffraction-limited soft x-ray storage ring is a 9BA lattice with two dispersion bumps for localized chromatic corrections. Although this lattice meets the very aggressive emittance goal, it offers limited margins in terms of dynamic aperture and momentum acceptance. In this paper we explore a different approach based on a 7BA lattice with distributed chromatic correction. This lattice relies heavily on longitudinal gradient bends and reverse bending in order to suppress the emittance so that despite fewer bends an emittance comparable to the baseline lattice can be reached albeit with larger dynamic aperture and momentum acceptance. We present linear optics design, trade-offs between achievable emittance and longitudinal stability, as well as the employed nonlinear tuning approach and the resulting performance of this alternate lattice.

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THPMK082

Micro Bunch Rotation and Coherent Undulator Radiation From a Kicked Beam

undulator, quadrupole, electron, radiation

4489

J.P. MacArthur
Stanford University, Stanford, California, USA
Z. Huang, J. Krzywinski, A.A. Lutman
SLAC, Menlo Park, California, USA

Recent observations of x-rays from a microbunched beam that has been kicked off-axis have shown coherent radiation at surprisingly large angles, in some cases reaching 30-50 uRad. Previous work on the topic has suggested that radiation at such large angles is inconsistent with classical radiation theory because microbunches cannot tilt. Here we show that, when kicked in a quadrupole lattice, microbunches can automatically tilt toward a new direction of propagation. This allows for coherent radiation farther off axis.

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THPML018

Modeling of Self-Modulated Laser Wakefield Acceleration Driven by Sub-Terawatt Laser Pulses

laser, electron, plasma, target

4690

C.-Y. Hsieh, S.-H. Chen
NCU, Chung Li, Taiwan
M.W. Lin
National Tsing-Hua University (NTHU), Hsinchu, Taiwan

Funding: This work has been supported by the Ministry of Science and Technology in Taiwan by grant MOST104-2112-M-008-013-MY3 and by grant MOST105-2112-M-007-036-MY3.
Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target*. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems**. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly.
* A. J. Goers et al., Phys. Rev. Lett. 115, 194802 (2015).
** E. Kaksis et al., Opt. Express 24, 25, 28915 (2016).

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THPML106

Electron Microscopy Inspired Setup for Single-Shot 4-D Trace Space Reconstruction of Bright Electron Beams

emittance, electron, detector, experiment

4909

J. Giner Navarro, D.B. Cesar, P. Musumeci
UCLA, Los Angeles, California, USA
R.W. Aßmann, B. Marchetti, D. Marx
DESY, Hamburg, Germany

Funding: This work has been partially supported by the National Science Foundation under Grant No. 1549132 and Department of Energy under award No. DE-SC0009914.
In the development of low charge, single-shot diagnostics for high brightness electron beams, Transmission Electron Microscopy (TEM) grids present certain advantages compared to pepper pot masks due to higher beam transmission. In this paper, we developed a set of criteria to optimize the resolution of a point projection image. However, this configuration of the beam with respect to the grid and detector positions implies the measurement of a strongly correlated phase space which entails a large sensitivity to small measurement errors in retrieving the projected emittance. We discuss the possibility of an alternative scheme by inserting a magnetic focusing system in between the grid and the detector, similar to an electron microscope design, to reconstruct the phase space when the beam is focused on the grid.

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THPML126

Design of High Efficiency High Power CW Linacs for Environmental and Industrial Applications

linac, cavity, simulation, solenoid

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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