A HIGH POLARIZATION AND HIGH QUANTUM EFFICIENCY PHOTOCATHODE USING A GAAS-ALGAAS SUPERLATTICE

A charge of 2.3 x 10(11) electrons in 2.5 ns at a laser wavelength of 757 nm with a corresponding quantum efficiency (QE) of 2.0% measured a t 752 nm was extracted from a -120 kV biased, 20 mm diameter, GaAs-AlG aAs superlattice photocathode. The maximum electron polarization measu red with material from the same wafer, but in a different system, was 71% at 757 nm for a QE of 1.0% measured at 752 nm. The quantity and te mporal distribution of the extracted charge is consistent with a space charge limitation, rather than a cathode charge limit. The performanc e of this type of cathode makes it a possible candidate for future lin ear colliders.