Improved Rare-Earth Emitter Hollow Cathode

An improvement has been made to the design of the hollow cathode geometry that was created for the rare-earth electron emitter described in “Compact Rare Earth Emitter Hollow Cathode” (NPO-44923), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 52. The original interior assembly was made entirely of graphite in order to be compatible with the LaB6 material, which cannot be touched by metals during operation due to boron diffusion causing embrittlement issues in high-temperature refractory materials. Also, the graphite tube was difficult to machine and was subject to vibration-induced fracturing.