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photocathodes in photoinjector

 
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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