Correlation of DC and Microsecond Pulsed Emission from Oxide Coated Cathodes

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Abstract
This report describes a study of dc and microsecond pulsed emission from oxide coated cathodes prepared on four different base metals. One of the base metals used was pure electrolytic nickel and the other three had impurities of 0.2 percent silicon, 4 percent silicon, and 4.7 percent tungsten added to the nickel. The flat base metal cathode was coated with equal molar barium-strontium carbonate. The tubes were placed on life test at a cathode temperature of 1125°K with no emission current drawn. Dc and pulsed emission measurements were taken periodically. Three methods were used to measure the zero field emission current, (1) dc retarding potential, (2) dc Schottky, and (3) pulsed Schottky. These gave essentially the same Richardson plot indicating a positive correlation of dc and pulsed emission. From these Richardson plots obtained using methods (1) and (3), the work function, the emission constant, and J0, the characteristic emission current density at 650°K, were determined. The results show that the different cathode base metals control the variation in emission with life. The emission from the tungsten-nickel base metal is stable with life and is of much higher value than the other base metals.

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