Author: Lewandowski, J.R.
Paper Title Page
TUAL2 Commissioning the New LCLS X-band Transverse Deflecting Cavity with Femtosecond Resolution 308
  • P. Krejcik, F.-J. Decker, Y. Ding, J.C. Frisch, Z. Huang, J.R. Lewandowski, H. Loos, J.L. Turner, J.W. Wang, M.-H. Wang, J.J. Welch
    SLAC, Menlo Park, California, USA
  • C. Behrens
    DESY, Hamburg, Germany
  Funding: This work was supported by Department of Energy Contract No. DE-AC0276SF00515
The new X-band transverse deflecting cavity began operation in May 2013 and is installed downstream of the LCLS undulator. It is operated at the full 120 Hz beam rate without interfering with the normal FEL operation for the photon users. The deflected beam is observed on the electron beam dump profile monitor, which acts as an energy spectrometer in the vertical plane. We observe, on a pulse by pulse basis, the time resolved energy profile of the spent electron beam from the undulator. The structure is powered from a 50 MW X-band klystron, giving a 48 MV kick to the beam which yields a 1 fs rms time resolution on the screen. We have measured the longitudinal profile of the electron bunches both with the FEL operating and with the lasing suppressed, allowing reconstruction of both the longitudinal profile of the incoming electron beam and the time-resolved profile of the X-ray pulse generated in the FEL. We are immediately able to see whether the bunch is chirped and which parts of the bunch are lasing, giving us new insight into tuning the machine for peak performance. The performance of the system will be presented along with examples of measurements taken during LCLS operation.
slides icon Slides TUAL2 [9.210 MB]  
TUPC05 Laser and Photocathode Gun Instrumentation for the ASTA Accelerator Test Stand at SLAC 357
  • J. Sheppard, W.J. Corbett, S. Gilevich, E.N. Jongewaard, J.R. Lewandowski, P. Stefan, T. Vecchione, S.P. Weathersby, F. Zhou
    SLAC, Menlo Park, California, USA
  An accelerator test stand has been constructed at SLAC to characterize laser-assisted photocathode processing, electron beam emission physics and front-end rf gun performance. The objective of the research program is to identify definitive ‘recipes’ for high-reliability cathode preparation resulting in high quantum efficiency and low beam emittance. In this paper we report on timing, optics and instrumentation for the Ti:Sapphire drive laser, diagnostics for the 1.6 cell photocathode gun and instrumentation for the resulting electron beam. The latter include a Faraday cup charge monitor, scintillator screen beam imaging for direct emittance measurements, and high-resolution imaging of the photocathode surface to diagnose the impact of laser processing for enhanced quantum efficiency.