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Frisch, J.C.

Paper Title Page
MOOCRA03 Femtosecond Synchronization of Laser Systems for the LCLS 58
 
  • J.M. Byrd, L.R. Doolittle, G. Huang, J.W. Staples, R.B. Wilcox
    LBNL, Berkeley, California
  • J. Arthur, J.C. Frisch, W.E. White
    SLAC, Menlo Park, California
 
 

The scientific potential of femtosecond x-ray pulses at linac-driven FELs such as the LCLS is tremendous. Time-resolved pump-probe experiments require a measure of the relative arrival time of each x-ray pulse with respect to the experimental pump laser. In order to achieve this, precise synchronization is required between the arrival time diagnostic and the laser which are often separated by hundreds of meters. We describe an optical timing system based on stabilized fiber links which has been developed for the LCLS to provide this synchronization. Preliminary results show stability of the timing distribution at the sub-10 fsec level and overall synchronization of the x-rays and pump laser of less than 40 fsec. We present details of the implementation and LCLS and potential for future development.

 

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Slides

 
MOPE070 Cavity Beam Position Monitor System for ATF2 1140
 
  • S.T. Boogert, G.E. Boorman, C. Swinson
    JAI, Oxford
  • R. Ainsworth, S. Molloy
    Royal Holloway, University of London, Surrey
  • A.S. Aryshev, Y. Honda, T. Tauchi, N. Terunuma, J. Urakawa
    KEK, Ibaraki
  • J.C. Frisch, J. May, D.J. McCormick, J. Nelson, T.J. Smith, G.R. White, M. Woodley
    SLAC, Menlo Park, California
  • A. Heo, E.-S. Kim, H.-S. Kim, Y.I. Kim
    Kyungpook National University, Daegu
  • A. Lyapin
    UCL, London
  • H.K. Park
    KNU, Deagu
  • M.C. Ross
    Fermilab, Batavia
  • S. Shin
    PLS, Pohang
 
 

The Accelerator Test Facility 2 (ATF2) in KEK, Japan, is a prototype scaled demonstrator system for the final focus required for a lepton linear collider. The ATF2 beam-line is instrumented with a total of 38 C and S band resonant cavity beam position monitors (BPM) with associated mixer electronics and digitizers. The current status of the BPM system is described, with a focus on operational techniques and performance.

 
TUPE065 Surface Characterization of the LCLS RF Gun Cathode 2284
 
  • A. Brachmann, F.-J. Decker, Y.T. Ding, D. Dowell, P. Emma, J.C. Frisch, A. Gilevich, G.R. Hays, P. Hering, Z. Huang, R.H. Iverson, H. Loos, A. Miahnahri, D. Nordlund, H.-D. Nuhn, P.A. Pianetta, J.L. Turner, J.J. Welch, W.E. White, J. Wu, D. Xiang
    SLAC, Menlo Park, California
 
 

Surface characterization of the LCLS RF gun cathode A. Brachmann On behalf of the LCLS commissioning team The first copper cathode installed in the LCLS RF gun was used during LCLS commissioning for more than a year. However, after high charge operation (~ 500 pC), the cathode showed a decline of quantum efficiency due to surface contamination caused by residual ionized gas species present in the vacuum system. We report results of SEM, XPS and XAS studies that were carried out on this cathode after it was removed from the gun. X-ray absorption and X-ray photoelectron spectroscopy reveal surface contamination by various hydrocarbon compounds. In addition we report on the performance of the second installed cathode with emphasis on the spatial distribution of electron emission.

 
TUPE066 Femtosecond Operation of the LCLS for User Experiments 2287
 
  • J.C. Frisch, C. Bostedt, J.D. Bozek, A. Brachmann, R.N. Coffee, F.-J. Decker, Y.T. Ding, D. Dowell, P. Emma, A. Gilevich, G. Haller, G.R. Hays, P. Hering, B.L. Hill, Z. Huang, R.H. Iverson, E.P. Kanter, B. Kraessig, H. Loos, A. Miahnahri, H.-D. Nuhn, A. Perazzo, M. Petree, D.F. Ratner, T.J. Smith, S.H. Southworth, J.L. Turner, J.J. Welch, W.E. White, J. Wu, L. Young
    SLAC, Menlo Park, California
  • R.B. Wilcox
    LBNL, Berkeley, California
 
 

In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering X-ray beams to users with energies between 800eV and 2 keV and with bunch lengths below 10 fs FWHM. A bunch arrival time monitor and timing transmission system provide users with sub 100 fs synchronization between a laser and the X-rays for pump / probe experiments. We describe the performance and operational experience of the LCLS for short bunch experiments.

 
TUPE071 Identifying Longitudinal Jitter Sources in the LCLS Linac 2296
 
  • F.-J. Decker, R. Akre, A. Brachmann, J. Craft, Y.T. Ding, D. Dowell, P. Emma, J.C. Frisch, Z. Huang, R.H. Iverson, A. Krasnykh, H. Loos, H.-D. Nuhn, D.F. Ratner, T.J. Smith, J.L. Turner, J.J. Welch, W.E. White, J. Wu
    SLAC, Menlo Park, California
 
 

The Linac Coherent Light Source (LCLS) at SLAC is an x-ray Free Electron Laser with wavelengths of 0.15 nm to 1.5 nm. The electron beam stability is important for good lasing. While the transverse jitter of the beam is about 10-20% of the rms beam sizes, the jitter in the longitudinal phase space is a multiple of the energy spread and bunch length. At the lower energy of 4.3 GeV (corresponding to the longest wavelength of 1.5 nm) the relative energy jitter can be 0.125%, while the rms energy spread is with 0.025% five times smaller. An even bigger ratio exists for the arrival time jitter of 50 fs and the bunch duration of about 5 fs (rms) in the low charge (20 pC) operating mode. Although the impact to the experiments is reduced by providing pulse-by-pulse data of the measured energy and arrival time, it would be nice to understand and mitigate the root causes of this jitter. The thyratron of the high power supply of the RF klystrons is one of the main contributors. Another suspect is the multi-pacting in the RF loads. Phase measurements down to 0.01 degree (equals 10 fs) along the RF pulse were achieved, giving hints to the impact of the different sources.