Cs2Te photocathode for the TTF Injector II

High quantum efficiency (Q.E.) (10-12 % @ 254 nm) cesium telluride (Cs2Te) photocathodes has been produced on different substrata. Photoemitter preparation procedure, gas exposition poisoning and rejuvenation effects have been investigated both from the photoemissive properties point of view (e.g. Q.E. vs. ? and vs. gas exposition) and for what is relative to the chemical structure and composition by using electron spectroscopy techniques as AES (Auger Electron Spectroscopy) and XPS (X-ray Electron Spectroscopy). A Cs2Te preparation system for the TTF injector II is under construction and it will be operative within autumn 1996 at Fermilab, where the gun prototype is being assembled. Moreover we are implementing the apparatus used at Milano for the photocathodes R&D activity with a 250 fs Nd:glass high power laser system and a new UHV analysis chamber: both will be used for optical measurements and low energy electron spectroscopy analysis as angle resolved photoemission.