Soviet Development of Needle-Tip Field-Emission Cathodes for High-Current Electron Beams.

Summarizes recent Soviet theoretical and experimental work on cathodes for very high-current charged particle beams, work led by Fursey at Leningrad State University and Mesyats at Tomsk. Field emission from needle-tip cathodes is based on explosive emission from the tips, accompanied by explosion-derived plasma setting up intense local electric fields. A cathode fabrication method is described that gives stable operation through 10,000 to 100,000 pulses of about 3 nanoseconds each, for currents of 500 to 1000 A. A liquid cathode produces stable current pulses within 6 percent of 2000 A. In a large needle array, 80 percent to 100 percent of the tips maintained current value dispersion within 20 percent. Operational cathodes of the controllable tip-and-dielectric type have been developed for 500 keV and 50 kA, and of the multiple-tip types for 1 MeV and 50 kA. Soviet scientists apparently feel that such beams can solve many problems, including controlled thermonuclear reactions, high-intensity microwave, flash X-rays and gamma rays, and high pressure effects in materials. 24 pp. Ref.