SILICON CATHODES WITH ARRAY OF TIPS USED AS PULSED PHOTOEMITTERS

Cathodes with array of tips made from silicon wafer previously tested under continuous laser and high local electric field have produced satisfactory results [Aboubacar et al., Nucl. Instrum. Method B 63, 489 (1992)]. These cathodes have been submitted to a pulsed laser beam in the range of few tens of nanoseconds to 35 ps duration at several optical frequencies. Fast time response, less than 400 ps (limitation of the scope), have been observed. This could be useful in future works for higher-frequency operation, such as the achievement and the development of very high-energy linear accelerators and photoinjectors for free-electron lasers. To enhance photocurrents triggered by laser pulses, photoemission using two colors has been realized. Some preliminary results and discussion are presented.