CARE 2004 - 2008


photocathodes in photoinjector

Activities in CARE/JRA
Useful links

Advanced electron injectors are based on photocathode electron guns. These guns can produces electron beams with short pulses and high brightness. At the beginning the progress in photo-injector development has been mainly driven by FEL applications. But now photo-injector is the electron source of choice for future linear colliders, high-power FELs, linear accelerators with energy recovery, fourth generation light sources, injectors for laser-driven plasma wake field accelerators, or low-energy electron linacs for applied research.

For all the different photo-injector systems the photocathodes play a key role. In strong connection with the laser system the choice of the optimum cathode type and its further improvement is a main issue for the progress in photo-injectors. In this website an overview of the existing knowledge of photo cathodes for rf photoelectron injectors is given and the status of the research and development of the CARE/JRA2 project is presented.

    The SRF-gun works in the ultra high vacuum, which does benefit to the operator lifetime of the photocathode. But it also has rigorous requirements for the cathode.
  1. Enough QE (>1%) in needed lifetime (~100 hours).
  2. Robust against strong laser shots
  3. The least contamination to Nb cavity
  4. Plug without C or H element on surface.
  5. The least heat load to SC cavity
  6. Tolerance to high RF field
  7. Lowest reflection for the drive laser
  8. ......
Cs2Te is a p-type semiconductor, and has been chosen as the candidate in several FEL projects, such as TESLA SASE FEL, Daresbury FEL, TEUFEL project, FELBE in HZDR, and so on. It keeps a good QE in hundred of hours, and has the possibility to stand the high RF field. More study is needed in its photoelectric performance under low temperature.

Last modified: January 17, 2005

Contact : R. Xiang