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Limborg-Deprey, C.

Paper Title Page
TUODC03 Parallel Finite Element Particle-In-Cell Code for Simulations of Space-charge Dominated Beam-Cavity Interactions 908
  • A. E. Candel, A. C. Kabel, K. Ko, L. Lee, Z. Li, C. Limborg-Deprey, C.-K. Ng, E. E. Prudencio, G. L. Schussman, R. Uplenchwar
    SLAC, Menlo Park, California
  Funding: U. S. DOE contract DE-AC002-76SF00515

Over the past years, SLAC's Advanced Computations Department (ACD) has developed the parallel finite element particle-in-cell code Pic3P (Pic2P) for simulations of beam-cavity interactions dominated by space-charge effects. As opposed to standard space-charge dominated beam transport codes, which are based on the electrostatic approximation, Pic3P (Pic2P) includes space-charge, retardation and boundary effects as it self-consistently solves the complete set of Maxwell-Lorentz equations using higher-order finite element methods on conformal meshes. Use of efficient, large-scale parallel processing allows for the modeling of photoinjectors with unprecedented accuracy, aiding the design and operation of the next-generation of accelerator facilities. Applications to the Linac Coherent Light Source (LCLS) RF gun are presented.

slides icon Slides  
TUPMS047 Results of the SLAC LCLS Gun High-Power RF Tests 1296
  • D. Dowell, E. N. Jongewaard, J. R. Lewandowski, Z. Li, C. Limborg-Deprey, J. F. Schmerge, A. E. Vlieks, J. W. Wang, L. Xiao
    SLAC, Menlo Park, California
  Funding: SLAC is operated by Stanford University for the Department of Energy under contract number DE-AC03-76SF00515.

The beam quality and operational requirements for the Linac Coherent Light Source (LCLS) currently being constructed at SLAC are exceptional, requiring the design of a new RF photocathode gun for the electron source. Based on operational experience at GTF at SLAC, SDL and ATF at BNL and other laboratories, the 1.6cell s-band (2856MHz) gun was chosen to be the best electron source for the LCLS injector, however a significant re-design was necessary to achieve the challenging parameters. Detailed 3-D analysis and design was used to produce nearly-perfect rotationally symmetric rf fields to achieve the emittance requirement. In addition, the thermo-mechanical design allows the gun to operate at 120Hz and a 140MV/m cathode field, or to an average power dissipation of 4kW. Both average and pulsed heating issues are addressed in the LCLS gun design. The first LCLS gun is now fabricated and has been operated with high-power RF. The results and analysis of these high-power tests will be presented.

TUPMS048 Measurement and Analysis of Field Emission Electrons in the LCLS Gun 1299
  • D. Dowell, E. N. Jongewaard, C. Limborg-Deprey, J. F. Schmerge, A. E. Vlieks
    SLAC, Menlo Park, California
  Funding: SLAC is operated by Stanford University for the Department of Energy under contract number DE-AC03-76SF00515.

The field emission was measured during the high-power testing of the LCLS photocathode RF gun. A careful study and analysis of the field emission electrons, or dark current is important in assessing the gun's internal surface quality in actual operation, especially those surfaces with high fields. The charge per 2 microsecond long RF pulse (the dark charge) was measured as a function of the peak cathode field for the 1.6 cell, 2.856GHz LCLS RF gun. Faraday cup data was taken for cathode peak RF fields up to 120MV/m producing a maximum of 0.6nC/RF pulse for a diamond-turned polycrystalline copper cathode installed in the gun. The field dependence of the dark charge is analyzed using a temperature-dependent Fowler-Nordheim (FN) theory to obtain the field enhancement factor and other emitter parameters. Digitized images of the dark charge were taken using a 100 micron thick YAG crystal for a range of solenoid fields to determine the location and angular distribution of the field emitters. The FN plots and emitter image analysis will be described in this paper.

TUPMS058 The LCLS Injector Drive Laser 1317
  • W. E. White, J. Castro, P. Emma, A. Gilevich, C. Limborg-Deprey, H. Loos, A. Miahnahri
    SLAC, Menlo Park, California
  Requirements for the LCLS injector drive laser present significant challenges to the design of the system. While progress has been demonstrated in spatial shape, temporal shape, UV generation and rep-rate, a laser that meets all of the LCLS specifications simultaneously has yet to be demonstrated. These challenges are compounded by the stability and reliability requirements. The drive laser and transport system has been installed and tested. We will report on the current operational state of the laser and plans for future improvements.  
TUPMS049 Initial Commissioning Experience with the LCLS Injector 1302
  • P. Emma, R. Akre, J. Castro, Y. T. Ding, D. Dowell, J. C. Frisch, A. Gilevich, G. R. Hays, P. Hering, Z. Huang, R. H. Iverson, P. Krejcik, C. Limborg-Deprey, H. Loos, A. Miahnahri, C. H. Rivetta, M. E. Saleski, J. F. Schmerge, D. C. Schultz, J. L. Turner, J. J. Welch, W. E. White, J. Wu
    SLAC, Menlo Park, California
  • L. Froehlich, T. Limberg, E. Prat
    DESY, Hamburg
  Funding: U. S. Department of Energy contract #DE-AC02-76SF00515.

The Linac Coherent Light Source (LCLS) is a SASE x-ray Free-Electron Laser (FEL) project presently under construction at SLAC. The injector section, from drive-laser and RF photocathode gun through the first bunch compressor chicane, was installed during the Fall of 2006. Initial system commissioning with an electron beam takes place in the Spring and Summer of 2007. The second phase of construction, including the second bunch compressor and the FEL undulator, will begin later, in the Fall of 2007. We report here on experience gained during the first phase of machine commissioning, including RF photocathode gun, linac booster section, energy spectrometers, S-band and X-band RF systems, the first bunch compressor stage, and the various beam diagnostics.

THPAS060 LCLS Beam Dynamics Studies with the 3-D Parallel Impact-T Code 3624
  • Y. T. Ding, Z. Huang, C. Limborg-Deprey
    SLAC, Menlo Park, California
  • J. Qiang
    LBNL, Berkeley, California
  In 2007, the Linac Coherent Light Source (LCLS) will start to commission the photoinjector, the linacs (up to 250 MeV) and the first bunch compressor (BC1). In this paper, we report on the beam dynamics studies in this low-energy part of the machine with the parallel Impact-T code*, taking into account three-dimensional (3-D) space charge forces, linac wakefields, and coherent synchrotron radiation. We compare the IMPACT-T simulation results with PARMELA and discuss possible space charge effects in the linac and BC1 regions. We also plan to compare with experimental measurements when they become available.

* J. Qiang et al, Phys. Rev. ST Accel. Beams 9,044204 (2006).