Production of polarized electron beam with sub-nanosecond multi-bunch structure from superlattice photocathode

Polarized electron beam with sub-nanosecond multi-bunch structure has been first produced from an In-GaAs-AlGaAs strained-layer superlattice photocathode with heavy surface doping. The extracted charge of 0.6 x 10(10)e(-)/bunch is determined by the space charge limit of the 50 keV gun. The multi-bunch effect due to the surface charge limit phenomenon, which is peculiar to a negative electron affinity surface of semiconductor photocathode, is not observed in the second bunch separated by 2.8 ns. We conclude that a superlattice photocathode with a heavily doped surface is the best photocathode for the future linear colliders. (C) 2000 Elsevier Science B.V. All rights reserved.