Relativistic electron beams from cathodes at 1 GV/m gradient

A high voltage pulser capable of delivering up to 1 MV with a duration of /spl sim/1 ns and rise and fall times of /spl sim/0.15 ns has been constructed and tested. Copper and stainless steel cathodes have been tested to withstand 1 GV/m gradient. Under background pressures of 10/sup -7/ Torr, the dark current is below the detection limit of our system at 1 GV/m gradient and hence would not contribute significantly to the photocurrent. Copper cathode and stainless steel anode have been shown to withstand applied fields of 1.7 GV/m without experiencing high voltage breakdown. Dark current measurements and Fowler-Nordheim plot for fields exceeding 1 GV/m indicate that surface fields experienced by these electrodes could be as high as 40 GV/m.