Keyword: scattering
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MOPWA025 Simulation of Laser Cooling of Heavy Ion Beams at High Intensities laser, synchrotron, ion, simulation 150
 
  • L. Eidam, O. Boine-Frankenheim, D.F.A. Winters
    GSI, Darmstadt, Germany
  
  In the past the principle of Doppler laser cooling was investigated and verified in storage rings in the low energy regime. Within the FAIR project the laser cooling will be applied to high intensity and high energy beams for the first time. The laser cooling results in a further increase of the longitudinal phase space density and in non-Gaussian longitudinal beam profiles. In order to ensure stable operation and optimize the cooling process the interplay of the laser force and high intensity effects has to be studied numerically. This contribution will identify constrains of the cooling scheme for an efficient reduction of momentum spread. For high beam energies the scattering of photons has to be treated stochastically instead of using averaged forces. The modeling of the laser force in a particle in cell tracking code will be discussed.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA025  
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MOPWA052 Formation of a Uniform Ion Beam Based on Nonlinear Focusing and its Applications at the JAEA TIARA Cyclotron ion, cyclotron, target, octupole 236
 
  • Y. Yuri, I. Ishibori, T. Ishizaka, S. Okumura, K. Yoshida, T. Yuyama
    JAEA/TARRI, Gunma-ken, Japan
  
  A formation/irradiation technique of large-area uniform beams based on nonlinear focusing of multipole magnets has been developed toward advanced research and efficient industrial applications at the TIARA AVF cyclotron of Japan Atomic Energy Agency. The uniform beam is formed as follows: An ion beam extracted from the cyclotron is multiply-scattered with a thin foil so that the transverse beam intensity distribution can be smoothed into a Gaussian-like distribution, critical to the formation of a highly uniform distribution. Then, the tail of the Gaussian-like distribution is folded into the inside by the nonlinear force of octupole magnets and eventually a uniform intensity distribution can be formed on a target. Typically, the area and uniformity of the beam are over 100 cm2 and below 10%, respectively. Such large-area uniform beams have already been applied to radiation degradation testing of space-use solar cells and a study on functional materials in TIARA. In the presentation, the latest R&D results and the utilization status of the uniform beam will be shown.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA052  
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MOPWA067 Theory of Transverse Ionization Cooling in a Linear Channel emittance, lattice, quadrupole, collider 279
 
  • M. Xiao, J. Gao, Y. Yue
    IHEP, Beijing, People's Republic of China
  
  Ionization cooling is the most hopeful method to reduce the emittance of muon beams, which plays an important role in neutrino factory and muon collider. Within the moment-equation approach, I present a way to derive the formulae of emittance in transverse under linear channel. All heating and coupling terms are reserved in the deriving process. From my formulae, it is a way to achieve a small emittance by designing the cooling channel compact to make the beta function changing sharply.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA067  
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MOPJE053 NSLS-II Beam Lifetime Measurements and Modeling cavity, emittance, coupling, lattice 416
 
  • B. Podobedov, W.X. Cheng, Y. Hidaka, H.-C. Hseuh, G.M. Wang
    BNL, Upton, Long Island, New York, USA
  
  NSLS-II is a recently constructed 3 GeV synchrotron light source with design horizontal emittance values in sub-nm range. Achieving good beam lifetime is critically important for NSLS-II as it is closely tied in to such important operational aspects as top-off injection frequency, injector components wear, radiation protection and control, and others. In this paper we present lifetime-related commissioning results, describe our present understanding of beam lifetime at NSLS-II and extrapolate our models to the fully built-up machine operating at 500 mA design beam current.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE053  
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MOPMA008 Simulation of Gas-Scattering Lifetime using Position- and Species-Dependent Pressure and Aperture Profiles vacuum, simulation, storage-ring, photon 546
 
  • M. Borland, J.A. Carter, H. Cease, B.K. Stillwell
    ANL, Argonne, Ilinois, 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.
When computing gas-scattering lifetime for storage rings, it is common to use the average pressure, even though it is known that the pressure varies with location in the ring and varies differently for different gas species. In addition, other simplifications are commonly made, such as assuming that the apertures in the horizontal and vertical planes are independent and assuming that the momentum acceptance can be characterized by a single value. In this paper, we describe computation of the elastic- and bremsstrahlung-scattering lifetimes that includes species-specific gas pressure profiles computed with VACCALC and MOLFLOW. In addition, the computations make use of the detailed shape of the dynamic acceptance and the position-dependent momentum acceptance. Comparisons are made to simpler methods for the Advanced Photon Source storage ring and the multi-bend achromat upgrade lattice. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA008  
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MOPMA012 Intra-Beam and Touschek Scattering Computations for Beam with Non-Gaussian Longitudinal Distributions emittance, distributed, simulation, lattice 559
 
  • A. Xiao, M. Borland
    ANL, Argonne, Ilinois, 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
Both intra-beam scattering (IBS) and the Touschek effect become prominent for multi-bend-achromat- (MBA-) based ultra-low-emittance storage rings. To mitigate the transverse emittance degradation and obtain a reasonably long beam lifetime, a higher harmonic rf cavity (HHC) is often proposed to lengthen the bunch. The use of such a cavity results in a non-gaussian longitudinal distribution. However, common methods for computing IBS and Touschek scattering assume Gaussian distributions. Modifications have been made to several simulation codes that are part of the {\tt elegant} toolkit to allow these computations for arbitrary longitudinal distributions. After describing these modifications, we review the results of detailed simulations for the proposed hybrid seven-bend-achromat (H7BA) upgrade lattice for the Advanced Photon Source. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA012  
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MOPMA031 Simulations of Diamond Detectors with Schottky Contacts electron, simulation, detector, photon 617
 
  • G.I. Bell, J.R. Cary, D.A. Dimitrov, D. Meiser, D.N. Smithe, C.D. Zhou
    Tech-X, Boulder, Colorado, USA
  • M. Gaowei, E.M. Muller
    SBU, Stony Brook, New York, USA
  • J. Smedley
    BNL, Upton, Long Island, New York, USA
  
  Funding: This work is supported by the US DOE Office of Science, department of Basic Energy Sciences, grant numbers DE-SC0006246 and DE-SC0007577.
We present simulations of semiconductor devices using the code VSim (formerly Vorpal). The 3D simulations involve the movement and scattering of electrons and holes in the semiconductor, voltages which may be applied to external contacts, and self-consistent electrostatic fields inside the device. Particles may experience a Schottky barrier when moving between the semiconductor and a metal contact. Example devices include MOSFETs as well as a diamond X-ray detector. Our code VSim includes scattering models for GaAs and diamond, and runs in parallel on thousands of processors. We compare our simulation results with experimental results from a prototype diamond X-ray detector. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA031  
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MOPMA033 Modeling Electron Emission and Surface Effects from Diamond Cathodes electron, simulation, cathode, vacuum 620
 
  • D.A. Dimitrov, J.R. Cary, D.N. Smithe, C.D. Zhou
    Tech-X, Boulder, Colorado, USA
  • I. Ben-Zvi, T. Rao, J. Smedley, E. Wang
    BNL, Upton, Long Island, New York, USA
  
  Funding: We are grateful to the U.S. DoE Office of Basic Energy Sciences for supporting this work under grants DE-SC0006246 and DE-SC0007577.
We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 to 17 MV/m along the [100] direction. The simulation results were compared to experimental data when using different emission models, band bending effects, and surface-dependent electron affinity. Simulations using surface patches with different levels of hydrogenation lead to the closest agreement with the experimental data. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA033  
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MOPMN018 A Generic Formulation for Emittance and Lattice Function Evolution for Non-Hamiltonian Systems with Stochastic Effects emittance, lattice, radiation, synchrotron 740
 
  • J.S. Berg
    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.
I describe a generic formulation for the evolution of emittances and lattice functions under arbitrary, possibly non-Hamiltonian, linear equations of motion. The average effect of stochastic processes, which would include ionization interactions and synchrotron radiation, is also included. I first compute the evolution of the covariance matrix, then the evolution of emittances and lattice functions from that. I examine the particular case of a cylindrically symmetric system, which is of particular interest for ionization cooling. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN018  
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MOPMN020 Longitudinal Impedance of RHIC synchrotron, impedance, experiment, storage-ring 746
 
  • M. Blaskiewicz, J.M. Brennan, K. Mernick
    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 longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. With Z/n about 5 Ω the impedance of the yellow ring is roughly twice that of the blue ring. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMN020  
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MOPHA007 Modeling/Measurement Comparison of Signal Collection in Diamond Sensors in Extreme Conditions electron, space-charge, detector, simulation 787
 
  • V. Kubytskyi, P. Bambade, S. Liu
    LAL, Orsay, France
  
  Here we present a study of charge collection dynamics in a Diamond Sensor (DS) subjected to intensities from 1 to 108 Minimum Ionizing Particles (MIP). We developed a model based on the numerical solution of the 1D drift-diffusion equations, using the Scharfetter-Gummel discretization scheme. Inhomogeneity of the space-charge distribution together with the externally applied electric field are taken into account by analytically solving the Poisson equation at each time step. We identified two regimes of charge collection. The first corresponds to 1-105 MIPs, in this case the externally applied electric field is negligibly perturbed by space-charge effects during the separation of the electron/hole clouds. The second corresponds to intensities larger than 107 MIPs, where the space-charge effects significantly slow down the charge collection due to large concentrations of electron/hole pairs in the DS volume. The results of our modeling are in qualitative agreement with the experimental data acquired at the PHoto-Injector electron beam facility at LAL. Our model allows optimizing DS parameters to achieve desired charge collection times for different beam intensities.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA007  
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TUBB3 Recent Progress of J-PARC RCS Beam Commissioning - Toward Realizing the 1-MW Output Beam Power injection, acceleration, operation, quadrupole 1346
 
  • H. Hotchi
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  Via a series of the injector linac upgrades in 2013 and 2014, the J-PARC RCS got all the design parameters. Thus the RCS is now in the final beam commissioning phase aiming for the 1-MW design output beam power. This paper presents the recent progress of the RCS beam commissioning, mainly focusing on our approaches to beam loss issues that appeared on the process of the beam power ramp-up.  
slides icon Slides TUBB3 [2.299 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUBB3  
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TUBC2 Multi-GHz Pulse-Train X-Band Capability for Laser Compton X-Ray and Gamma-Ray Sources laser, electron, brightness, photon 1363
 
  • D.J. Gibson, G.G. Anderson, S.G. Anderson, C.P.J. Barty, R.A. Marsh, M. J. Messerly, M.A. Prantil
    LLNL, Livermore, California, USA
  
  Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
A wide variety of light-source applications would benefit from increased average brightness, which generally corresponds to increasing average current in the driving accelerator. Presented is an accelerator architecture that is capable of producing hundreds of electron bunches, spaced as close together as every RF cycle, which provides the chance to increase current while maintaining beam quality. This system relies on an X-band photoinjector and a photoinjection drive laser that is driven by the same rf source to ensure synchronization, and an interaction laser system designed to match the duty cycle of the electron pulse train. Results of the photoinjector laser performance and initial experimental measurements of beam quality in accelerated bunch trains are presented, along with a discussion of the impact on the performance of tunable, narrow-bandwidth x-ray and gamma-ray beams based on Compton-scattering. 		 
slides icon Slides TUBC2 [20.256 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUBC2  
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TUPWA016 Modeling of beam losses at ESRF vacuum, simulation, electron, detector 1430
 
  • R. Versteegen, P. Berkvens, N. Carmignani, J. Chavanne, L. Farvacque, S.M. Liuzzo, B. Nash, T.P. Perron, P. Raimondi, K.B. Scheidt, S.M. White
    ESRF, Grenoble, France
  
  As the ESRF enters the second phase of its upgrade towards ultra low emittance, the knowledge of the beam loss pattern around the storage ring is needed for radiation safety calculations and for the new machine design optimization. A model has been developed to simulate the Touschek scattering and the scattering of electrons on residual gas nuclei in view of producing a detailed loss map of the machine. Results of simulation for the ESRF are presented and compared with real beam measurements.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA016  
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TUPWA059 Modeling of Photoemission and Electron Spin Polarization from NEA GaAs Photocathodes electron, polarization, simulation, photon 1556
 
  • O. Chubenko, A. Afanasev
    GWU, Washington, USA
  
  Funding: Work supported by The George Washington University and Thomas Jefferson National Accelerator Facility.
Many nuclear-physics and particle-physics scientific laboratories, including Thomas Jefferson National Accelerator Facility, Newport News, VA 23606 (Jefferson Lab) which studies parity violation and nucleon spin structure, require polarized electron sources. At present, photoemission from strained GaAs activated to negative electron affinity (NEA) is a main source of polarized electrons. Future experiments at advanced electron colliders will require highly efficient polarized electron beams, which sets new requirements for photocathodes in terms of high quantum efficiency (QE) (>>1%) and spin polarization (~85%). Development of such materials includes modeling and design of photocathodes, material growth, fabrication of photocathodes, and photocathode testing. The purpose of the present work is to develop a semi-phenomenological model, which could predict photoemission and electron spin polarization from NEA GaAs photocathodes. Detailed Monte Carlo simulation and modeling of physical processes in photocathodes is important for optimization of their design in order to achieve high QE and reduce depolarization mechanisms. Electron-phonon interactions near the surface and influence of the presence of quantum heterostructures on the diffusion length are studied in depth. Simulation results will be compared to the experimental results obtained at Jefferson Lab and can be used to optimize the photocathode design and material growth, and thus develop high-polarization high-brightness electron source. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA059  
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TUPWA072 Coherent Thomson Scattering Radiation Generated by using PEHG radiation, electron, laser, undulator 1601
 
  • S. Chen, K. Ohmi, D. Zhou
    KEK, Ibaraki, Japan
  • S. Huang
    PKU, Beijing, People's Republic of China
  
  In this paper, we present the coherent Thomson scattering of a long wavelength laser with ultrashort electron slices. The ultrashort electron slices are generated by the longitudinal bunch density modulation method of PEHG. Coherent radiation with ultrashort pulse length is generated in EUV regime by this method.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWA072  
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TUPJE010 Study of Cs-Te Photocathode for RF Electron Gun electron, gun, vacuum, radiation 1632
 
  • S. Matsuzaki, M. Nishida, K. Sakaue, M. Washio
    Waseda University, Tokyo, Japan
  • H. Iijima
    Tokyo University of Science, Tokyo, Japan
  
  At Waseda University, we have been studying high quality electron beam with an rf electron gun. In recent accelerator study and application researches, high quality electron beam are strongly required. Photocathode is a key component to generate higher quality electron beam. Cs-Te photocathode shows high quantum efficiency (Q.E.) (~10%) and has long life time (~several months). From 2013, we built a photocathode evaporation chamber and started photocathode study. In this study, our purpose is to clarify their property and to establish an ideal evaporation recipe. We succeeded in producing high quality Cs-Te photocathode, and electron beam generated by our Cs-Te photocathode shows high charge (4.6nC/bunch) and high Q.E. (1.74%) in our rf electron gun. Furthermore, we found a Q.E. recovery after Cs deposition process and it causes higher Q.E. than usual due to, we believe, Cs deposition quantity or Cs deposition speed. Thus we are now surveying the optimum Cs evaporation parameters. In this conference, we will report a detail of our photocathode development system, the latest progress of optimization study of Cs-Te photocathode and future plans.
Work supported by Cooperative and Supporting Program for Researches and Educations in Universities and NEDO(New Energy and Industrial Technology Development Organization. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE010  
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TUPJE013 Lattice Design of Low Beta Function at Interaction Point for TTX-II lattice, electron, quadrupole, dynamic-aperture 1641
 
  • T. Rui, W.-H. Huang
    TUB, Beijing, People's Republic of China
  
  TTX-II is a storage ring being designed at Accelerator Laboratory in Tsinghua University as the second phase of Tsinghua Thomson scattering x-ray source (TTX), to increase the average photon flux generated. To achieve a small beta function at the interaction point, four pairs of quadrupole magnets, whose focusing strengths are optimized, are added to the baseline. The lattice design is presented in this work.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE013  
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TUPJE021 Interaction Chamber Design for a Sub-MeV Laser-compton Gamma-ray Source laser, electron, photon, simulation 1665
 
  • H.H. Xu, J.H. Chen, G.T. Fan, D. Wang, H.L. Wu, B.J. Xu
    SINAP, Shanghai, People's Republic of China
  
  Previously, fixed angle Laser-Compton Scattering (LCS) experiments have been conducted at the terminal of the 100MeV LINAC of the Shanghai Institute of Applied Physics, using SINAP-I* and SINAP-II** facility. Sub-MeV energy continuously tunable laser-Compton light source device (SINAP-Ⅲ) is an updated facility that will allow the collision angle between the laser and electron beam continuously adjustable from 20 to 160 degrees. This new feature will enable convenient control on the peak energy of the generated X/γ ray, especially when the energy of electrons cannot be momentarily adjusted, e.g. on the storage ring. The well control of the status of LCS is necessary. An interaction chamber containing a rotatable structure that holds a series of plane mirrors and convex lens is presented to achieve it. This work is a summary of its design. The simulation of photon production's variation caused by the system errors is performed using a MC code***. The accuracies of installation and adjustment of mirrors and lens are given according to the simulation results. The sizes of these optical devices are also optimized to make the chamber as compact as possible due to space limitation.
* W. Luo et al., Rev. of Sci. Instrum, 81 (2010) 013304
** W. Luo et al., Applied Physics B, 101 (2010)761-771
*** W. Luo et al., NIM A, 660 (2011), p. 108
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPJE021  
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TUPMA030 Narrowband Continuously Tunable Radiation in the 5 to 10 Terahertz Range by Inverse Compton Scattering electron, laser, radiation, photon 1901
 
  • Z. Wu, K. Fang, M.-H. Wang, J. Wu
    SLAC, Menlo Park, California, USA
  
  Funding: Work supported by U.S. Department of Energy under Grants DE-AC02-76SF00515, DE-FG02-13ER41970 and by DARPA Grant N66001-11-1-4199.
5 to 10 THz has recently become the frontier of THz radiation sources development, pushed by the growing interests of spectroscopy and pump-probe material study in this frequency range. This spectrum “Gap” lies in between the several THz range covered by Electro-Optical crystal based THz generation, and the tens of THz range covered by the difference frequency generation method. The state-of-the-art EO crystal THz source using tilted pulse front technique has been able to reach ~ 100 MV/m peak field strength, large enough to be used in an inverse Compton scattering process to push these low energy photons to shorter wavelengths of the desired 5-10 THz range. The required electron beam energy is within 1~2 MeV, therefore a compact footprint of the whole system. The process would occur coherently granted the electron beam is bunched to a fraction of the radiation wavelengths (several microns). A system operating at KHz or even MHz repetition rate is possible given the low electron energy and thus low RF acceleration gradient required. This work will explore the scheme with design parameters and simulation results. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPMA030  
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TUPTY004 Tracking Simulation for Beam Loss Studies with Application to FCC simulation, lattice, collider, detector 2004
 
  • M. Boscolo
    INFN/LNF, Frascati (Roma), Italy
  • H. Burkhardt
    CERN, Geneva, Switzerland
  
  We present an implementation of a tracking simulation tool used to evaluate the main particle loss effects for Flavor Factories with the aim of applying these studies also to FCC. We describe the interface of the Monte Carlo tracking code with MAD-X, showing first simulations of the Touschek effect for the FCC-ee at the Z. We plan to use this approach also for multi-turn simulations of particles scattered by radiative Bhabha, beam-gas and eventually Beamstrahlung effects.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY004  
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TUPTY016 Study of Background and MDI Design for CEPC background, detector, photon, simulation 2028
 
  • Y. Yue, Q. Qin
    IHEP, Beijing, People's Republic of China
  
  CEPC is a project designed to obtain a large number of Higgs events by keeping e+e− collisions at the center-of-mass energy of 240 GeV and deliver peak luminosity above 1034 cm-2 s-1 for each interaction point. The super high energy and the pretty high luminosity will bring some special background problems, which will exert difficulty on the MDI design and the detectors protection. In this article, I will show the simulation result of the main background sources at CEPC and give some suggestions on the MDI design and detectors protection.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY016  
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TUPTY029 Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials collimation, simulation, impedance, proton 2068
 
  • E. Quaranta, R. Bruce, A. Mereghetti, S. Redaelli, A. Rossi
    CERN, Geneva, Switzerland
  
  The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY029  
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TUPTY080 Synchrotron Radiation Analysis of the SuperKEKB Positron Storage Ring photon, positron, electron, vacuum 2222
 
  • J.A. Crittenden, D. Sagan
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • T. Ishibashi, Y. Suetsugu
    KEK, Ibaraki, Japan
  
  Funding: US National Science Foundation contracts PHY-0734867, PHY-1002467, and PHY-1068662, US Department of Energy contract DE-FC02-08ER41538 and the Japan/US Cooperation Program.
We report on modeling results for synchrotron radiation absorption in the SuperKEKB positron storage ring vacuum chamber including the effects of photon scattering on the interior walls. A detailed model of the geometry of the inner vacuum chamber profile has been developed and used as input to a photon tracking code. Particular emphasis is placed on the photon absorption rates in the electron-positron interaction region. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY080  
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TUPWI017 Single-shot Multi-MeV Ultrafast Electron Diffraction on VELA at Daresbury Laboratory electron, gun, FEL, experiment 2278
 
  • L.K. Rudge, D. Angal-Kalinin, J.A. Clarke, F. Jackson, J.K. Jones, A. Kalinin, S.L. Mathisen, J.W. McKenzie, B.L. Militsyn, B.D. Muratori, T.C.Q. Noakes, Y.M. Saveliev, D.J. Scott, P.H. Williams
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  • P. Aden, R.J. Cash, D.M.P. Holland, M.D. Roper
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  • P.D. Lane, D.A. Wann
    University of York, York, United Kingdom
  • M. Surman
    STFC/DL/SRD, Warrington, Cheshire, United Kingdom
  • J.G. Underwood
    UCL, London, United Kingdom
  
  Funding: This work was funded by STFC
Accelerator based Ultrafast Electron Diffraction (UED) is a technique for obtaining static structures and for studying sub-100 fs dynamic structural changes on the atomic scale. In this paper we present the first electron diffraction results obtained from the VELA accelerator in 2014. The accelerator was operated to provide typically 4MeV/c electron bunches. Diffraction patterns were observed with <<1 pC transported to the detection screen. Single shot and multi-shot accumulated diffraction data are presented from single crystal and polycrystalline samples, including Au, Al, Pt and C. Contamination of the diffraction pattern with dark current contributions is an issue. A variable size aperture directly in front of the sample offers some mitigation, but at the expense of reduced charge contributing to the diffraction pattern. We discuss future developments for electron diffraction on VELA including further beam optimization, measurement of bunch length with a newly installed Transverse Deflecting Cavity, and the planned developments for pump-probe studies. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWI017  
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TUPWI027 Radiography Capabilities for Matter-Radiation Interactions in Extremes electron, proton, quadrupole, linac 2295
 
  • P.L. Walstrom, R.L. Barber, C.A. Chapman, R.W. Garnett, T.S. Gomez, J.A. O'Toole, H.R. Salazar
    LANL, Los Alamos, New Mexico, USA
  
  Funding: This work is supported by the U. S. Department of Energy Contract DE-AC52-06NA25396.
The Matter-Radiation Interactions in Extremes (MaRIE) experimental facility will be used to discover and design the advanced materials needed to meet 21st century national security and energy security challenges. This new facility will provide the new tools scientists need to develop next-generation materials that will perform predictably and on-demand for currently unattainable lifetimes in extreme environments. The MaRIE facility is based on upgrades to the existing LANSCE 800-MeV proton linac and a new 12-GeV electron linac and associated X-ray FEL to provide simultaneous multiple probe beams, and new experimental areas. In addition to the high-energy photon probe beam, both electron and proton radiography capabilities will be available at the MaRIE facility. Recently, detailed radiography system studies have been performed to develop conceptual layouts of high-magnification electron and proton radiography systems that can meet the experimental requirements for the expected first experiments to be performed at the facility. A description of the radiography systems, their performance requirements, and a proposed facility layout will be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPWI027  
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WEAB3 Intra-beam Scattering Effects in ELENA antiproton, emittance, electron, simulation 2458
 
  • J. Resta-López, J.R. Hunt, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • J.R. Hunt, J. Resta-López, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  
  Funding: Work supported by the EU under Grant Agreement 624854 and the STFC Cockcroft Institute core Grant No. ST/G008248/1.
Intra-Beam Scattering (IBS) is one of the main limiting processes for the performance of low energy ion storage rings, such as the Extra Low ENergy Antiproton ring (ELENA) that is being constructed at CERN. IBS effects limit the achievable equilibrium 6D beam phase space volume during the cooling process, as well as the stored beam intensity. In this contribution we analyze the IBS effects on the beam dynamics of the ELENA ring in detail. Numerical simulations using the codes BETACOOL and MAD-X have been performed to compute the beam life time and the equilibrium phase space parameters with electron cooling in the presence of IBS. 		 
slides icon Slides WEAB3 [6.222 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEAB3  
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WEPWA044 The Alignment of the MICE Tracker Detectors alignment, emittance, experiment, detector 2597
 
  • M.A. Uchida
    Imperial College of Science and Technology, Department of Physics, London, United Kingdom
  
  The Muon Ionization Cooling experiment (MICE) has been designed to demonstrate the reduction of the phase-space volume (cooling) occupied by a muon beam using the ionization-cooling technique. This demonstration will be an important step in establishing the feasibility of muon accelerators for particle physics. The emittance of the beam will be measured before and after the cooling cell using a solenoidal spectrometer. Each spectrometer will be instrumented with a high-precision scintillating-fibre tracking detector (Tracker). The Trackers will be immersed in a uniform magnetic field of 4T and will measure the normalised emittance reduction with a precision of 0.1%. A thorough knowledge of the alignment of the Trackers is essential for this accuracy to be achieved. The Trackers are aligned: mechanically inside the spectrometer solenoids, with respect to the MICE experimental hall, to one another, and to the magnetic and beam axes. These methods are described here.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA044  
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WEPWA047 Emittance Growth in a Plasma Wakefield Accelerator plasma, emittance, electron, wakefield 2609
 
  • Ö. Mete, K. Hanahoe, G.X. Xia
    UMAN, Manchester, United Kingdom
  • M. Labiche
    STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
  
  The interaction of the witness beam with the surrounding plasma particles and wakefields was studied. The implications of the elastic scattering process on beam emittance and, emittance evolution under the focusing and acceleration provided by plasma wakefields were discussed. Simulations results from GEANT4 are presented in this paper.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA047  
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WEPWA049 Low Energy Beam Tracking Under Scattering for a Cold Electron Source in Manchester electron, emittance, extraction, experiment 2615
 
  • R.B. Appleby, W. Bertsche, O. Mete, G.X. Xia
    UMAN, Manchester, United Kingdom
  • M.A. Harvey, M. Jones, A.J. Murray
    The University of Manchester, The Photon Science Institute, Manchester, United Kingdom
  • B. Kyle
    University of Manchester, Manchester, United Kingdom
  
  High quality electron beams, with high spatial and temporal resolution, have an important use in electron diffraction experiments to probe and study the constituents of matter. A cold electron source is being developed based on electron ionisation from an atom cloud trapped by using AC magneto-optical methods in the University of Manchester. The technique will produce bunches of electrons well suited for high precision and single shot electron diffraction. In this paper issues of modelling at low energies for this state of art electron source with very low energy spread are presented, with a focus on newly developed tools to model the scattering in the meshes used to support the extraction electric fields. The dependence on emittance growth on mesh wire thickness is studied.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA049  
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WEPWA066 The Advancement of Cooling Absorbers in COSY Infinity simulation, electron, controls, proton 2655
 
  • J.D. Kunz
    IIT, Chicago, Illinois, USA
  • M. Berz, K. Makino
    MSU, East Lansing, Michigan, USA
  • P. Snopok
    Illinois Institute of Technology, Chicago, Illlinois, USA
  
  Funding: Work is supported by the U.S. Department of Energy.
COSY Infinity is an arbitrary-order beam dynamics simulation and analysis code. It can determine high-order transfer maps of combinations of particle optical elements of arbitrary field configurations. For precision modeling, design, and optimization of next-generation muon beam facilities, its features make it a very attractive code. New features are being developed for inclusion in COSY to follow the distribution of charged particles through matter. To study in detail some of the properties of muons passing through material, the transfer map approach alone is not sufficient. The interplay of beam optics and atomic processes must be studied by a hybrid transfer map–Monte-Carlo approach in which transfer map methods describe the average behavior of the particles in the accelerator channel including energy loss, and Monte-Carlo methods are used to provide small corrections to the predictions of the transfer map accounting for the stochastic nature of scattering and straggling of particles. The advantage of the new approach is that it is very efficient in that the vast majority of the dynamics is represented by fast application of the high-order transfer map of an entire element and accumulated stochastic effects as well as possible particle decay. The gains in speed are expected to simplify the optimization of muon cooling channels which are usually very computationally demanding due to the need to repeatedly run large numbers of particles through large numbers of configurations. Progress on the development of the required algorithms is reported. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA066  
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WEPJE025 Phase Space Density as a Measure of Cooling Performance for the International Muon Ionization Cooling Experiment emittance, simulation, luminosity, experiment 2726
 
  • J.S. Berg
    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 International Muon Ionization Cooling Experiment (MICE)* is an experiment to demonstrate ionization cooling of a muon beam in a beamline that shares characteristics with one that might be used for a muon collider or neutrino factory. I describe a way to quantify cooling performance by examining the phase space density of muons, and determining how much that density increases. This contrasts with the more common methods that rely on the covariance matrix and compute emittances from that. I discuss why a direct measure of phase space density might be preferable to a covariance matrix method. I apply this technique to an early proposal for the MICE final step beamline. I discuss how matching impacts the measured performance.
* http://mice.iit.edu/ I am not a MICE collaboration member, and nothing herein should be construed as representing the work or views of the collaboration. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPJE025  
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WEPHA025 Design of a Variable X-band RF Power Splitter network, impedance, polarization, operation 3167
 
  • H. Zha, A. Grudiev, D. Gudkov, I. Syratchev
    CERN, Geneva, Switzerland
  
  The design of a two output ports, high power X-Band RF splitter with arbitrary split ratio is presented. This ratio is adjusted by mechanical changing the position a special RF short circuit piston. The piston is mounted on a step-motor providing the precise movement. Special measures were taken in the design to decrease the maximum electrical field on the cooper surface, as well as to maximise the bandwidth of the device. This splitter will be tested in the high power X-band test stand at CERN.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA025  
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WEPHA060 5MW Power Upgrade Studies of the ISIS TS1 Target target, neutron, proton, simulation 3253
 
  • C. Bungau, A. Bungau, R. Cywinski, T.R. Edgecock
    University of Huddersfield, Huddersfield, United Kingdom
  • C.N. Booth, L. Zang
    Sheffield University, Sheffield, United Kingdom
  
  The increasing demand for neutron production at the ISIS neutron spallation source has motivated a study of an upgrade of the production target TS1. This study focuses on a 5 MW power upgrade and complete redesign of the ISIS TS1 spallation target, reflector and neutron moderators. The optimisation of the target-moderator arrangement was done in order to obtain the maximum neutron output per unit input power. In addition, at each step of this optimisation study, the heat load and thermal stresses were calculated to ensure the target can sustain the increase in the beam power.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPHA060  
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WEPTY012 Multiple Scattering Effects of a Thin Beryllium Window on a Short, 2 nC, 60 MeV Bunched Electron Beam simulation, vacuum, experiment, emittance 3280
 
  • E.E. Wisniewski, M.E. Conde, W. Gai, G. Ha, J.G. Power
    ANL, Argonne, Illinois, USA
  • G. Ha
    POSTECH, Pohang, Kyungbuk, Republic of Korea
  
  Funding: U.S. Dept of Energy Office of Science under contract number DE-AC02-06CH11357.
The Argonne Wakefield Accelerator 75 MeV drive beamline at Argonne National Laboratory has as its electron source a Cesium telluride photocathode gun with a vacuum requirement on the order of 10-10 torr. In conflict with this, the experimental program at AWA sometimes requires beamline installation of experimental structures which due to materials and/or construction cannot meet the stringent vacuum requirement. One solution is to sequester these types of structures inside a separate vacuum chamber and inject the beam through a thin Beryllium window. The downside is that multiple scattering effects degrade the beam quality to some degree which is not well-known. This study was done in an effort to better understand and predict the multiple scattering effects of the Be thin window, particularly on the beam transverse size. The results of measurements are compared with GEANT4 Monte Carlo simulations via G4beamline and analytical calculations via GPT. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY012  
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WEPTY054 Grid Window Tests on an 805-MHz Pillbox Cavity Windows, cavity, radiation, controls 3393
 
  • Y. Torun
    Illinois Institute of Technology, Chicago, Illlinois, USA
  • A. Moretti
    Fermilab, Batavia, Illinois, USA
  
  Funding: Supported by the US Department of Energy Office of Science through the Muon Accelerator Program.
Muon ionization cooling channel designs use pillbox shaped RF cavities for improved power efficiency and fine control over phasing of individual cavities. For minimum scattering of the muon beam, the ends should be made out of a small thickness of high radiation length material. Good electrical and thermal conductivity are required to reduce power dissipation and remove the heat efficiently. Thin curved beryllium windows with TiN coating have been used successfully in the past. We have built an alternative window set consisting of grids of tubes and tested these on a pillbox cavity previously used with both thin Be and thick Cu windows. The cavity was operated with a pair of grids as well as a single grid against a flat endplate. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPTY054  
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THPF098 SPS-to-LHC Transfer Lines Loss Map Generation Using PyCollimate collimation, simulation, proton, injection 3934
 
  • F.M. Velotti
    EPFL, Lausanne, Switzerland
  • W. Bartmann, C. Bracco, M.A. Fraser, B. Goddard, V. Kain, M. Meddahi, F.M. Velotti
    CERN, Geneva, Switzerland
  
  The Transfer Lines (TL) linking the Super Proton Synchrotron (SPS) to the Large Hadron Collider (LHC) are both equipped with a complete collimation system to protect the LHC against mis-steered beams. During the setting up of these collimators, their gaps are positioned to nominal values and the phase-space coverage of the whole system is checked using a manual validation procedure. In order to perform this setting-up more efficiently and more reliably, the simulated loss maps of the TLs will be used to validate the collimator positions and settings. In this paper, the simulation procedure for the generation of TL loss maps is described, and a detailed overview of the new scattering routine (pycollimate) is given. Finally, the results of simulations benchmark with another scattering routine are presented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THPF098  
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THPF102 Verification of the Neutron Mirror Capabilities in MCNPX via Gold Foil Measurements at the EIGER Instrument Beamline at the Swiss Spallation Neutron Source (SINQ) neutron, target, simulation, proton 3949
 
  • R.M. Bergmann, U. Filges, S.H. Forss, E. Rantsiou, D. Reggiani, T. Reiss, U. Stuhr, V. Talanov, M. Wohlmuther
    PSI, Villigen PSI, Switzerland
  
  The EIGER triple-axis thermal neutron spectrometer beamline contains “supermirror” neutron guides, which preferentially reflect low-energy neutrons toward the EIGER spectrometer that come from the ambient temperature, light water neutron source in SINQ. Gold foil measurements have been performed at the EIGER beamline in 2013. This process can be modeled from incident proton to thermal neutron exiting the EIGER beamline by using the neutron mirror capabilities of MCNPX, which should be more accurate than simulations with simplified neutron source distributions and geometry representations. The supermirror reflectivity parameters have been measured previously and are used in MCNPX 2.7.0 to reproduce the activity measured from the gold foil irradiation, verifying the neutron mirror modeling capabilities in MCNPX 2.7.0.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THPF102  
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THPF125 MARS Tracking Simulations for the Mu2e Slow Extracted Proton Beam extraction, septum, simulation, beam-losses 4010
 
  • V.P. Nagaslaev, I.L. Rakhno
    Fermilab, Batavia, Illinois, USA
  
  Particle tracking taking into account interactions with fields and materials is necessary for proper evaluation of the resonant extraction losses and geometry optimization for the extraction beam line. This paper describes the tracking simulations for the Mu2e Resonant Extraction and discusses the geometry choices made based on these simulations.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-THPF125  
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