Development of a durable, large area cathode for repetitive, uniform electron beam generation

Electra is a large aperture krypton-fluoride laser under development for inertial fusion energy research. The laser will require dual 500 kV, 36 A/cm/sup 2/, uniform electron beams operating at 5 Hz. Experimental studies have been performed to develop a /spl sim/3000 cm/sup 2/ cathode capable of generating a 110 kA, 100 ns flat top beam pulse with minimal current density variation (<10%), fast rise time (<40 ns), negligible gap closure (<1 cm//spl mu/s), and long lifetime (ultimately 10/sup 8/ shots). Time resolved electrical and optical data from the study of various dielectric fiber, carbon, and metal/dielectric cathodes are discussed.