The operation of a cold electron source with a cryogenic GaAs photocathode will enable electron-ion interactions to be studied at the Heidelberg TSR with a much enhanced energy resolution. A unique facility for preparing cesium- and oxygen- activated GaAs photocathodes and for measuring the energy spread of photoemitted electrons has been developed over recent years and was now used to analyze for the rst time two-dimensional energy distributions. These measurements indicate unexpected strong contributions of elastic scattering in the surface layer of GaAs(Cs,O). Different structures of the GaAs(CS,O) surface and various thicknesses of the activation (Cs,O) layer have been investigated with the aim to reduce electron scattering near the interface and to increase the transmission of cold electrons through the narrow residual surface barrier. The photocathode performance data promise electron beams of several 10 mA=cm 2 with longitudinal and transverse energies 10 meV.


Talk Slides:



(Coffee & Cookies before the seminar starting 10:00 am)