Non-Thermionic Cathode for High Power Long Pulse, Long Lifetime Magnetrons.

摘要

Report developed under STTR contract for topic AF08-BT14. There is considerable interest in adapting the conventional Magnetron Oscillator tube for use in High Power Microwave applications. A major obstacle in this is that the conventional thermionic cathode doses not provide acceptable electron emission for operation in the HPM power levels (> 100Mw). In this work, we explore the potential for using arrays of sharpened microscopic carbon fibers to provide field emitted electrons at room temperature and without plasma generation. This study builds on previous work with single carbon fibers in which adequate cold emission was observed. We describe experimental results in which approximately 1 square cm arrays containing approximately 10,000 individual fibers were studied. Initial explosive emission (including plasma formation and diode shorting) was observed. Careful conditioning techniques were developed to suppress this process and to eventually produce very long pulse (approximately seconds), uniform field emission. The effects of pulse rise time, diode vacuum, Cesium Iodide coating and emission field levels are discussed. Finally, the results of 3 dimensional particle-in- cell simulation of a Magnetron tube geometry are described.