A novel thin film dispenser cathode for thermionic emission

Abstract

Abstract. A thin film dispenseror micro-dispensercathode can be generatedusing standard rf sputteringdeposition technology. These films are compositionallymodulated structures based on W and a multi-componentBa oxide. Annealing to temperatures horn 900 to 1300K results in Ba reduction, transport and diffision across the emitter surface.A finite temperaturerange exists(< 1200K)where a uniformRe coatingcan be retainedat the emittersurface. The metallic coating results in a nearly homogeneouswork finction based on emission characteristics.These films produce stable emissionat higher temperatures(2 1200K)where the uniform Re coating is lost. Analysisof emission properties yield a work function of 2.2 eV and an apparent emission coefilcient of 6 A"cm-2"K-2 after annealingto 1200K.This high apparent emission coefficient yields a film suitable for milliwatt power generation applications. MicrominiatureThermionicConverters(MTCS)are one potentialapplicationfor these films.

Desorption from Hot Scandate Cathodes: Effects on Vacuum Device Interior Surfaces after Long-Term Operation

“…Thermionic cathodes are electron sources used in a wide range of vacuum electron devices (VEDs) critical to both military and civilian applications. Examples include devices based on RF amplifying traveling wave tubes-satellite communication systems and military/civilian RADAR applications [1]), miniature thermionic diodes [2], and more [3,4]. To meet increasing demand, high-power cathodes are being sought for THz or mm-wave devices [5] operating beyond the crowded kHz, MHz, and GHz frequency ranges.…”