Author: Krejcik, P.
Paper Title Page
MOPC41 Engineering Design of the New LCLS X-band Transverse Deflecting Cavity 167
  • P. Krejcik, E.L. Bong, M. Boyes, S. Condamoor, J.P. Eichner, G.L. Gassner, A.A. Haase, B. Hong, B. Morris, J.J. Olsen, D.W. Sprehn, J.W. Wang
    SLAC, Menlo Park, California, USA
  Funding: This work was supported by Department of Energy Contract No. DE-AC0276SF00515
This paper describes the engineering design and installation of the new X-band transverse deflecting cavity installed downstream of the FEL undulator at the LCLS. This is a companion submission to the paper “Commissioning the New LCLS X-Band Transverse Deflecting Cavity with Femtosecond Resolution” also presented at this conference. The project dealt with the challenge of installing a new high-power RF system in the undulator tunnel of the LCLS, outside of the linac tunnel itself and its accelerator engineering infrastructure. A description of the system design, installation, alignment, cooling, controls, vacuum, waveguide, low level RF, klystron and modulator systems for the XTCAV is given, with emphasis on achieving the performance goals necessary to achieve femtosecond resolution.
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]  
SLAC LCLS Cavity BPM Upgrade Project  
  • P. Krejcik
    SLAC, Menlo Park, California, USA
  Patrick summarized the experience of the SLAC LCLS X-Band (11.4 GHz) cavity BPM system, which has been in operation for several years. Even though the system meets the requirements, some of the original design ideas proved to be not optimal in practice, e.g. the ridged waveguide coupling between pickup and receiver, the pickup support structure, complex tuning of the BPM resonators, etc. Based on this experience Patrick presented a redesigned cavity-BPM pickup, with a loaded-Q ~2000. It now utilizes a waveguide-to coaxial transition, and semi-flexible coaxial cables to connect to the RF electronics. Detailed EM simulations, including an analysis of mechanical tolerances has been performed at SLAC, a prototype has been produced in collaboration with PAL (Pohang Accelerator Laboratory, South Korea). The new pickup design is also more relaxed on tolerances, thus the tight tuning requirements could be reduced. A prototype has been installed at LCLS, and the first beam tests are underway. There was a question addressed to the material, copper vs. Cu-plated stainless steel: SLAC has got years of experience brazing copper, so this is preferred material. The answer to another question, the x-y cross talk: 20dB before, 30dB after tuning.  
slides icon Slides FRWMJ1 [1.023 MB]