Explosive emission and gap closure from a relativistic electron beam diode

Explosive emission cathode studies are currently being conducted on a high power relativistic electron beam diode. A black velvet cathode is driven with a 75 Ohm graded transmission line, which provides a 3.8 MV, 80 ns (FWHM) pulse across a fixed A-K gap of 17.8 cm. Cathode sizes range from 1.9-7 cm with space-charge limited currents of 0.26-3 kA. The principal objective of these experiments is to quantify the current emission limits and the dynamics of the gap closure process. A qualitative comparison of experimental and calculated results are presented, which included the I-V relationship, impedance and perveance curves, plasma expansion velocity, and the time-resolved light emission on the surface of the cathode.