MC5: Beam Dynamics and EM Fields
D08 High Intensity in Linear Accelerators - Space Charge, Halos
Paper Title Page
TUPAB206 Matching of Intense Beam in Six-Dimensional Phase Space 1897
 
  • Y.K. Batygin
    LANL, Los Alamos, New Mexico, USA
 
  Funding: Work supported by US DOE under contract 89233218CNA000001
Beam matching is a common technique that is routinely employed in accelerator design to minimize beam losses. Despite being widely used, a full theoretical understanding of beam matching in 6D phase space remains elusive. Here, we present an analytical treatment of 6D beam matching of a high-intensity beam onto an RF structure. We begin our analysis within the framework of a linear model, and apply the averaging method to attain a matched solution for a set of 3D beam envelope equations. We then consider the nonlinear regime, where the beam size is comparable with the separatrix size. Starting with a Hamiltonian analysis in 6D phase space, we attain a self-consistent beam profile and show that it is significantly different from the commonly used ellipsoidal shape. Subsequently, we analyze the special case of equilibrium with equal space charge depression between all degrees of freedom. A comparison of beam dynamics for equipartitioned, equal space charge depression, and equal emittances beams is given.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB206  
About • paper received ※ 14 May 2021       paper accepted ※ 28 May 2021       issue date ※ 24 August 2021  
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WEPAB093 Space Charge Effects in Low Energy Magnetized Electron Beam 2806
 
  • S.A.K. Wijethunga, J.R. Delayen, G.A. Krafft
    ODU, Norfolk, Virginia, USA
  • J.F. Benesch, G.A. Krafft, M.A. Mamun, M. Poelker, R. Suleiman, S. Zhang
    JLab, Newport News, Virginia, USA
 
  Funding: This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177 and Laboratory Directed Research and Development program.
Magnetized electron cooling is one of the major approaches towards obtaining the required high luminosity in the proposed Electron-Ion Collider (EIC). In order to increase the cooling efficiency, a bunched electron beam with a high bunch charge and high repetition rate is required. At Jefferson Lab, we generated magnetized electron beams with high bunch charge using a new compact DC high voltage photogun biased at -300 kV with bialkali-antimonide photocathode and a commercial ultra-fast laser. This contribution discusses how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, and laser pulse width, and spot size in comparison with simulations performed using General Particle Tracer.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB093  
About • paper received ※ 19 May 2021       paper accepted ※ 08 June 2021       issue date ※ 02 September 2021  
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WEPAB251 Beam Dynamics Optimization of LCLS-II HE Linear Accelerator Design 3224
 
  • J. Qiang
    LBNL, Berkeley, California, USA
  • T.O. Raubenheimer, M.D. Woodley
    SLAC, Menlo Park, California, USA
 
  The LCLS-II-HE as a high energy upgrade of the high repetition rate X-ray FEL under construction at SLAC will provide great opportunities for scientific discovery by generating coherent, high brightness hard X-ray radiation. In this paper, we report on beam dynamics optimization of the LCLS-II HE linear accelerator design with a 100pC and a 20pC charge beam to attain high quality electron beam for X-ray FEL radiation. We also present preliminary results of beam dynamics optimization of a 100pC beam from a low emittance superconducting injector.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB251  
About • paper received ※ 18 May 2021       paper accepted ※ 21 June 2021       issue date ※ 30 August 2021  
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WEPAB254 Design of a 10 MeV Beamline at the Upgraded Injector Test Facility for e-Beam Irradiation 3232
 
  • X. Li, H. Baumgart, G. Ciovati
    ODU, Norfolk, Virginia, USA
  • G. Ciovati, F.E. Hannon, S. Wang
    JLab, Newport News, Virginia, USA
 
  Funding: Jefferson lab LDRD.
Electron beam irradiation near 10 MeV is suitable for wastewater treatment. The Upgraded Injector Test Facility (UITF) at Jefferson Lab is a CW superconducting linear accelerator capable of providing an electron beam of energy up to 10 MeV and up to 100 µA current. This contribution presents the beam transport simulations for a beamline to be used for the irradiation of wastewater samples at the UITF. The simulations were done using the code General Particle Tracer with the goal of obtaining an 8 MeV electron beam of radius (3-σ) of ~2.4 cm. The achieved energy spread is ~74.5 keV. The space charge effects were investigated when the bunch charge is varied to be up to 1000 times and the results showed that they do not affect the beam quality significantly.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB254  
About • paper received ※ 20 May 2021       paper accepted ※ 25 June 2021       issue date ※ 13 August 2021  
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WEPAB256 Three-Dimensional Space Charge Oscillations in a Hybrid Photoinjector 3240
 
  • M. Carillo, M. Behtouei, F. Bosco, L. Faillace, A. Giribono, L. Giuliano, M. Migliorati, A. Mostacci, L. Palumbo
    Sapienza University of Rome, Rome, Italy
  • L. Ficcadenti
    INFN-Roma, Roma, Italy
  • J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • B. Spataro, C. Vaccarezza
    INFN/LNF, Frascati, Italy
 
  Funding: This work supported by DARPA GRIT under contract no. 20204571 and partially by INFN National committee V through the ARYA project.
A new hybrid C-band photo-injector, consisting of a standing wave RF gun connected to a traveling wave structure, operating in a velocity bunching regime, has shown to produce an extremely high brightness beam with very low emittance and a very high peak current through a simultaneous compression of the beam in the longitudinal and transverse dimensions. A beam slice analysis has been performed in order to understand the evolution of the relevant physical parameters of the beam in the longitudinal and transverse phase spaces along the structure. A simple model for the envelope equation has been developed to describe the beam behavior in this particular dynamics regime that we term "triple waist", since all three dimensions reach a minimum condition almost simultaneously. The model analyzes the transverse envelope dynamics at the exit of the hybrid photo-injector, in the downstream drift where the triple waist occurs. The analytical solutions obtained from the envelope equation are compared with the simulations, showing a good agreement. Finally, these results have been analyzed also in terms of plasma oscillation to obtain a further physical interpretation of the beam dynamics.
 
poster icon Poster WEPAB256 [1.162 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB256  
About • paper received ※ 19 May 2021       paper accepted ※ 21 July 2021       issue date ※ 13 August 2021  
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WEPAB258 Beam Dynamics Design of a 162.5 MHz Superconducting RFQ Accelerator 3248
 
  • Ying. Xia, H.P. Li, Y.R. Lu, Q.Y. Tan, Z. Wang
    PKU, Beijing, People’s Republic of China
  • Y.R. Lu
    IAP, Frankfurt am Main, Germany
 
  Superconducting(SC) RFQ has lower power consumption, larger aperture and higher accelerating gradient than room temperature RFQ. We plan to design a 162.5MHz SC RFQ to accelerate the 30 mA proton beams from 35 keV to 2.5 MeV, which will be used as a neutron source for BNCT and neutron imaging project. At an inter-vane voltage of 180kV, the beam dynamics design was carried out with acceptable peak surface electric field, high transmission efficiency, and relatively short cavity length.  
poster icon Poster WEPAB258 [1.251 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB258  
About • paper received ※ 17 May 2021       paper accepted ※ 06 July 2021       issue date ※ 14 August 2021  
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WEPAB259 Impact of the Magnet Alignment and Field Errors on the Output Uniform Beam at the DONES HEBT Line 3251
 
  • C. Oliver, A. Ibarra, J. Mollá, I. Podadera, R. Varela
    CIEMAT, Madrid, Spain
  • H. Dzitko
    F4E, Germany
  • O. Nomen, D. Sánchez-Herranz
    IREC, Sant Adria del Besos, Spain
 
  Funding: This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053
IFMIF-DONES will be a facility devoted to study the degradation of advanced materials for operation of fusion reactors. Motivated by the need of optimizing the neutron irradiation to the materials samples, the HEBT line of the deuteron DONES (DEMO Oriented Neutron Source) accelerator is based on non-linear magnetic fields. By using octupoles and dodecapoles magnets, it is possible to shape the beam profile to achieve the demanded rectangular uniform distribution across the flat top of the beam profile, with high edge peaks in the horizontal direction. Special optics conditions are obtained with a proper setting of quadrupole magnets to minimize the x-y coupling. Additionally, the high beam power (5 MW, for a 125 mA, 40 MeV deuteron beam) in conjunction with the huge space charge makes challenging the HEBT line design to avoid non-controlled losses, except in the devoted scrapers. A comprehensive beam dynamics analysis has been made using TraceWin code. It includes extensive error studies to define tolerances and verify the robustness of the design with respect to magnet misalignment, power supply instabilities and injection parameters.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB259  
About • paper received ※ 19 May 2021       paper accepted ※ 26 July 2021       issue date ※ 17 August 2021  
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THXA01 Beyond RMS: Understanding the Evolution of Beam Distributions in High Intensity Linacs 3681
 
  • K.J. Ruisard, A.V. Aleksandrov, S.M. Cousineau, A.P. Shishlo, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
Understanding the evolution of beams with space charge is crucial to design and operation of high intensity linacs. While the community holds a broad understanding of the mechanisms leading to emittance growth and halo formation, there is outstanding discrepancy between measurements and beam evolution models that precludes prediction of halo losses. This may be due in part to insufficient information of the initial beam distribution. This talk will describe work at the SNS Beam Test Facility to directly measure the 6D beam distribution. Full-and-direct 6D measurement has revealed hidden but physically significant dependence between the longitudinal distribution and transverse coordinates. This nonlinear correlation is driven by space charge and reproduced by self-consistent simulation of the RFQ. Omission of this interplane correlation, common when bunches are reconstructed from lower-dimensional measurements, degrades downstream predictions. This talk will also describe the novel diagnostics supporting this work. This includes ongoing improvements to efficiency of the 6D phase space measurement as well as recent achievement of six orders of dynamic range in 2D phase space.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA01  
About • paper received ※ 20 May 2021       paper accepted ※ 23 July 2021       issue date ※ 17 August 2021  
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THPAB220 Multibunch Studies for LCLS-II High Energy Upgrade 4219
 
  • R.J. England, K.L.F. Bane, Z. Li, T.O. Raubenheimer, M.D. Woodley
    SLAC, Menlo Park, California, USA
  • M. Borland
    ANL, Lemont, Illinois, USA
  • A. Lunin
    Fermilab, Batavia, Illinois, USA
 
  Funding: The work is supported in part by DOE Contract No. DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) X-ray free-electron laser at SLAC is being upgraded to LCLS-II with a superconducting linac and 1 MHz bunch repetition rate. The proposed high-energy upgrade (LCLS-II-HE) will increase the beam energy from 4 to 8 GeV, extending the reach of accessible X-ray photon energies. With the increased repetition rate and longer linac of LCLS-II-HE, multi-bunch effects are of greater concern. We use recently introduced capabilities in the beam transport code ELEGANT to study dipole and monopole beam breakup effects for LCLS-II HE beam parameters. The results indicate that resonant dipole kicks have steady-state settle times on the order of 500 bunches or less and appear manageable. We also consider a statistical variation of the cavity frequencies and transverse offsets of cavities and quadrupoles. Resonant emittance growth driven by monopole kicks is found to be disrupted by frequency variation between cavities.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB220  
About • paper received ※ 19 May 2021       paper accepted ※ 15 July 2021       issue date ※ 21 August 2021  
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