Author: Jongewaard, E.N.
Paper Title Page
THP030 Recent Photocathode R&D for the LCLS injector 769
  • F. Zhou, A. Brachmann, W.J. Corbett, M.J. Ferreira, S. Gilevich, E.N. Jongewaard, J.R. Lewandowski, J. Sheppard, T. Vecchione, S. Vetter, S.P. Weathersby
    SLAC, Menlo Park, California, USA
  Funding: US DOE under contract No. DE-AC02-76SF00515
Systematic studies of the copper photocathodes identical to those used in the LCLS injector gun has been carried out at SLAC’s RF gun test facility. Recent observations at the gun test facility indicate that the pre-cleaning of the cathode prior to the installation in the gun is the major cause of the lower initial QE (~10-6) in the RF gun. All of four cathodes tested in the gun test facility have reliable higher initial QE, 4-8·10-5, with removal of pre-cleaning step. All of details will be described in the paper. A robust laser-assisted processing recipe has been developed. With this recipe, QE can be repeatedly evolved to about 1x10-4 within 3-4 weeks following the laser processing, and within 1-2 days the emittance is recovered to the values as observed prior to the laser processing. When compared to previous recipe used for the present LCLS cathode, the new recipe uses lower laser fluence and provides faster emittance recovery. Laser pointing stability is a key requirement for the success of the technique. This paper presents all details of the studies for four cathodes with over a few tens of laser-assisted spots and compares the results with the present LCLS cathode.