Self-breakdown statistics of a high-pressure spark gap with a microarray graphite cathode.

ABSTRACT

Comparative measurements with high-pressure spark gaps (gas pressure 0.2-0.9 MPa nitrogen, gap spacing 5 mm) are presented, one with a regular Bruce-profile polished graphite cathode (diameter 25 mm, thickness 8 mm) and the other with a microarray graphite cathode of equal dimensions. By microstructuring, a V-type graphite microarray is created by purpose-developed laser treatment of a plane graphite electrode. The microarray graphite cathode brings more initial plasma and then produces more initial electrons. It is beneficial for electron emission, which improves the stability of the switch breakdown. The experimental results are achieved at a gas pressure of 0.9 MPa and a 200-kV voltage pulse applied to the switch. With these parameters, the mean breakdown voltage is 91.7 kV, the minimum is 91.4 kV, and the mean relative standard deviation in breakdown voltage of the first 100 shots is 0.4%. Compared to a plane graphite cathode, the mean breakdown voltage is about 10% lower, and the mean relative standard deviation is reduced by more than 90%. The main result can be stated that microarray graphite cathodes are a suitable choice as electrodes for low-jitter high-pressure spark gaps.