Ultra-cold electron source with a GaAs-photocathode

A source of ultra-cold magnetically guided DC electron beams with a transmission mode GaAs-photocathode has been developed. The mA currents and the required stability are obtained by using state-of-the-art technology of photocathode fabrication and cleaning in UHV. To optimize energy spreads from photocathodes, studies of the complete (longitudinal and transverse) energy distribution of the magnetized electron beam were performed. They allowed us to get a detailed look on the energy loss and momentum scattering of the electrons at the interface and finally, to obtain narrow electron energy spreads (below 10 meV) from the photocathode.