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Ding, Y. T.

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TUOCAB02 Measurements of Compression and Emittance Growth after the First LCLS Bunch Compressor Chicane 807
  • P. Emma, K. L.F. Bane, Y. T. Ding, J. C. Frisch, Z. Huang, H. Loos, G. V. Stupakov, J. Wu
    SLAC, Menlo Park, California
  • E. Prat
    DESY, Hamburg
  • F. Sannibale, K. G. Sonnad, M. S. Zolotorev
    LBNL, Berkeley, California
  Funding: U. S. Depertment of Energy contract #DE-AC02-76SF00515.

The Linac Coherent Light Source (LCLS) is a SASE x-ray free-electron laser project presently under construction at SLAC. The injector section from RF photocathode gun through the first bunch compressor chicane was installed during the Fall of 2006. The first bunch compressor chicane is located at 250 MeV and nominally compresses a 1-nC electron bunch from an rms length of about 1 mm to 0.2 mm. The degree of compression is highly adjustable using RF phasing and also chicane magnetic field variations. Transverse phase space and bunch length diagnostics are located immediately after the chicane. We present measurements and simulations of the longitudinal and transverse phase space after the chicane in various beam conditions, including extreme compression where coherent radiation effects are expected to be striking.

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TUPMS046 Integration of the Optical Replica Ultrashort Electron Bunch Diagnostics with the Current-Enhanced SASE in the LCLS 1293
  • Y. T. Ding, P. Emma, Z. Huang
    SLAC, Menlo Park, California
  In this paper, we present a feasibility study of integrating the optical replica (OR) ultrashort electron bunch diagnostics * with the current-enhanced SASE (ESASE) scheme ** in the LCLS. Both techniques involve using an external laser to energy-modulate the electron beam in a short wiggler and converting the energy modulation to a density modulation in a dispersive section. While ESASE proposes to use the high-current spikes to enhance the FEL signal, the OR method extracts the optical coherent radiation produced by a density modulated electron beam for frequency resolved optical gating (FROG) diagnostics. We discuss the optimization studies of combining the OR method with the ESASE after the second bunch compressor in the LCLS. Simulation results show that the OR method is capable of reproducing the expected double-horn current profile of a 200-fs bunch. The possibilities and limitations of reconstructing the longitudinal phase space profile are also explored.

* E. Saldin et al, Nucl. Instr. and Meth. A 539, 499 (2005).** A. Zholents, Phys. Rev. ST Accel. Beams 8, 040701 (2005); A. Zholents et al., in Proceedings of FEL2004, 582 (2004).

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).