Research on the Emission Uniformity of Explosive Emission Cathodes in Foilless Diodes

• Published in: IEEE transactions on plasma science Vol. 42; no. 9; pp. 2179 - 2185
• Main Authors: Sun, Jun, Wu, Ping, Huo, Shaofei, Tan, Weibing, Shao, Hao, Chen, Changhua, Liu, Guozhi
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.09.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Annular; Blades; Cathode morphology; Cathodes; Defects; Diodes; EEC; Electric fields; Emission; emission uniformity; Energy efficiency; Explosions; explosive emission cathodes (EECs); Explosives; foilless diodes; high-power microwave (HPM); Microwave theory and techniques; Microwaves; Plasmas; Surface morphology; Surface treatment; Variability; high-power microwave (HPM); Cathode morphology; foilless diodes; emission uniformity; explosive emission cathodes (EECs)
• ISSN: 0093-3813; 1939-9375
• DOI: 10.1109/TPS.2014.2338301

Some factors that influence the emission uniformity of explosive emission cathodes (EECs) in foilless diodes such as the guiding magnetic field strength and the rise rate of electric field have been researched in former literatures. This paper is concentrated on another factor that has been overlooked previously, i.e., the defects with dimensions of tens of micrometers on cathode surfaces, especially at blade edges. It is shown that these defects will significantly worsen the emission uniformity of EECs by introducing extraordinarily large microscopic field enhancement factors, and thus they should be eliminated. The micrometer-scale irregularities, however, should be maintained to provide effective emission micropoints. Meanwhile, the outer edge of an annular cathode blade should be rounded off to improve the emission uniformity. After being disposed like this, the emission uniformity of annular graphite cathodes in a foilless diode is obviously improved, which leads to an increase of energy efficiency by more than 20% by broadening the microwave pulse duration under a power level of 2.8 GW for an X-band relativistic backward wave oscillator.