HIGH-EFFICIENCY PHOTOEMISSION FROM CS-K-TE

Cs-K-Te films have been fabricated under ultrahigh vacuum by vapor dep osition of Te, K, and Cs onto a Mo substrate into the preparation cham ber of the free electron laser of the University of Twente. Their phot oemission properties are reported in this letter. The average quantum efficiency at 259 nm measured on 5 evaporated Cs-K-Te photocathodes is 22.5%, whereas the best quantum efficiency obtained at 259 nm is 23.4 %. To our knowledge, this is the highest quantum efficiency at 259 nm reported so far, being about twice that of Cs,Te photocathodes. The re ported results demonstrate that Cs-K-Te photocathodes are very promisi ng for the use in photoinjectors. (C) 1997 American Institute of Physi cs.