Author: van der Geer, S.B.
Paper Title Page
TUPAB085 Three-Dimensional Radiative Effects in the Compression of Ultra-Short Electron Micro-Bunches 1577
 
  • R. Robles, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  Funding: DOE Contract DE-SC0009914 DOE Contract DE-SC0020409 National Science Foundation Grant No. PHY-1549132
Micro-bunched current profiles have recently gained traction as an alternative to bulk compression in certain free-electron laser applications. The attraction of the micro-bunched structure is owed in part to its promise to minimize deleterious effects associated with coherent synchrotron radiation during compression. Simultaneously, these profiles push the boundaries of traditional one-dimensional CSR simulation models which assume the bunch length to far exceed the transverse beam size in the bunch rest frame - an assumption which may be violated by the sub-micron length micro-bunches. Here we present simulation studies of the impact of three-dimensional CSR effects on micro-bunching based compression schemes using the General Particle Tracer code. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB085  
About • paper received ※ 19 May 2021       paper accepted ※ 23 June 2021       issue date ※ 13 August 2021  
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WEPAB104 Improving the Operational Lifetime of the CEBAF Photo-Gun by Anode Biasing 2840
 
  • J.T. Yoskowitz, G.A. Krafft, G.G. Palacios Serrano, S.A.K. Wijethunga
    ODU, Norfolk, Virginia, USA
  • J.M. Grames, J. Hansknecht, C. Hernandez-Garcia, M. Poelker, M.L. Stutzman, R. Suleiman
    JLab, Newport News, Virginia, USA
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
The operating lifetime of GaAs-based photocathodes in DC high voltage electron photo-guns is dominated by the ionization rate of residual beamline gas molecules. In this work, experiments were performed to quantify the improvement in photocathode charge lifetime by biasing the photo-gun anode with a positive voltage, which repels ions generated downstream of the anode. The photo-cathode charge lifetime improved by almost a factor of two when the anode was biased compared to the usual grounded configuration. Simulations were performed using the particle tracking code General Particle Tracer (GPT) with a new custom element. The simulation results showed that both the number and energy of ions play a role in the pattern of QE degradation. The experiment results and conclusions supported by GPT simulations will be presented. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB104  
About • paper received ※ 20 May 2021       paper accepted ※ 02 June 2021       issue date ※ 18 August 2021  
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WEPAB105 Simulating Electron Impact Ionization Using a General Particle Tracer (GPT) Custom Element 2843
 
  • J.T. Yoskowitz, G.A. Krafft
    ODU, Norfolk, Virginia, USA
  • J.M. Grames
    JLab, Newport News, Virginia, USA
  • G.R. Montoya Soto
    Universidad de Guanajuato, División de Ciencias e Ingenierías, León, Mexico
  • C.A. Valerio
    ECFM-UAS, Culiacan, Sinaloa, Mexico
  • S.B. van der Geer
    Pulsar Physics, Eindhoven, The Netherlands
  
  Funding: U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177, Consejo Nacional de Ciencia y Tecnología (CONACYT).
A new C++ custom element has been developed with the framework of General Particle Tracer (GPT) to simulate electron impact ionization of residual gas molecules. The custom element uses Monte-Carlo routines to determine both the ion production rate and the secondary electron kinetic energy based on user-defined gas densities and theoretical values for the ionization cross section and the secondary electron differential cross section. It then uses relativistic kinematics to track the secondary electron, the scattered electron, and the newly formed ion after ionization. The ion production rate and the secondary electron energy distribution determined by the custom element have been benchmarked against theoretical calculations and against simulations made using the simulation package IBSimu. While the custom element was originally built for particle accelerator simulations, it is readily extensible to other applications. The custom element will be described in detail and examples of applications at the Thomas Jefferson National Accelerator Facility will be presented for ion production in a DC high voltage photo-gun. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB105  
About • paper received ※ 20 May 2021       paper accepted ※ 25 June 2021       issue date ※ 19 August 2021  
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