Explosive electron emission from a surface-modified carbon/carbon composite cathode

Abstract

There has been continuous interest in carbon fibre cathodes applied in the area of explosive field emission. Carbon fibre cathodes have advantages of uniform electron emission, slow plasma expansion rate, low out-gassing rate and long lifetime. In this paper, electron emission properties of carbon/carbon (C/C) composite cathodes with and without surface modification were investigated in a diode powered by a ∼226 kV, 122 ns pulsed voltage in a single pulse mode. Scanning electron micrographs of the surface of the surface-modified C/C composite cathode indicated an explosive electron emission, which is consistent with the emission mechanism for bare carbon fibre cathodes. Compared with the as-received C/C cathode, the surface-modified C/C cathode demonstrates superior emission properties at the same applied voltage and anode–cathode gap, including lower turn-on field, higher emission current and shorter current delay time. The plasma expansion velocity for the C/C cathodes is estimated to be 5.0 ± 0.5 cm µs−1. The C/C composite cathode with proper surface modification has shown promise in electron-beam-driven sources such as high-power microwave devices.