Abstract
An electron source featuring high brightness and long life has been developed for high-resolution video recording. The electron source is of triode type, and incorporates a directly heated and replaceable lanthanum hexaboride (LaB6) emitter.Since the initial work of Lafferty (1) in 1951, LaB6 has been known as a potential long-life emitter material capable of high emission densities. However, a number of drawbacks have prevented widespread application as a cathode material. These include the high reactivity of LaB6 at elevated temperatures with almost all substrate materials, its sensitivity to corrosion by oxygen-containing gases (2), and fabrication problems due to Its brittleness. Successful operation at high emission densities, therefore, has been reported only by Kapitza, et al (3), and by Broers (4). Kapitza soldered an LaB6 cube to a tantalum heater using MoSi2 in vacuo at 2000°C. This system required a heating current of 50 A. Broers brazed an LaB6 rod to a copper heatsink and indirectly heated the tip of the rod by means of a tungsten coil requiring a power input of 60 W.
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