PHOTOEMISSION-STUDIES ON LAB6 AND PURE METALS USING A NANOSECOND KRF EXCIMER-LASER

The CAEP RF accelerator will use a photocathode rf gun to provide a hi gh brighness electron beam for FEL experiments. To achieve long lifeti me, our photocathode development initially concentrates on LaB6 and so me pure metals. We report experiments on these materials with a pulsed KrF excimer laser. Using surface heating and laser cleaning (surface activation), the quantum efficiency is dramatically enhanced. The quan tum efficiencies of LaB6, Y, Ag and Al are about 6.1 X 10(-4), 3.8 X 1 0(-4), 2.8 X 10(-4), and 1.4 X 10(-4), respectively. Using the pepper pot method, the nomalized beam emittances for these materials are abou t 10 rr mm mrad and the corresponding normalized brightnesses are abou t 10(10) A/m(2) rad(2). These photocathodes will be tested on the 1 1/2 cell microwave cavity at CAEP.