Preparation and electron emission properties of carbon fiber composited graphite cathodes

Abstract

As the source of intense electron beam, the cathodes have an important effect on the performance of high power microwave source. Graphite is a common material for explosive emission cathodes of high power microwave source, which have the advantages of stable operation and long life under high pressure and repetition frequency. The carbon fiber with high aspect ratio and low emission threshold was chosen to be composited with the graphite cathode, and the field emission and high power microwave test platforms were adopted to analyse field emission properties, intense electron emission performances and output microwave characteristics of pure graphite cathodes and carbon fiber composited graphite cathodes. Meanwhile the effect of carbon fiber on the electron emission properties of graphite cathodes was studied combined with the microstructure characterization of the cathodes. The results show that compared with the flake graphite cathodes, the field emission threshold of 40%(mass fraction) carbon fiber composited graphite cathodes decreases from 143 kV/cm to 119 kV/cm, a reduction of about 16.8%, and the output pulse width and peak of 480 kV increase by 13.5% and 5.7%, respectively. Considering the structural stability of carbon-fiber in the process of explosive electron emission, the carbon-fiber is also beneficial for improving the service life of the cathodes.

Keywords

• high power microwave source
• graphite cathode
• carbon fiber composite
• field emission