Fundamental Properties of the High Pressure Hydrogen Microdischarges in Static and Time-Varying Electric Fields

In this paper, the results of measurements of the characteristics of the hydrogen microdischarges from direct current to radio frequencies are presented and discussed. Two types of the electrode configurations are used: electrodes with Bruce profile and glass melting electrodes separated between 2.5 and 100 μm. The breakdown voltage values for low frequencies are similar to the direct current breakdown voltage data, while the high-frequency breakdown voltages are systematically lower. As the frequency increases, the breakdown voltage decreases in the case of glass melting electrodes and increases in the case of electrodes with Bruce profile. It is observed that the breakdown voltages that correspond to the melting glass electrodes are lower due to edge issues and inability to achieve a homogenous field. The effective yields estimated from the measured breakdown voltage curves are similar for both electrode configurations. In addition to the breakdown voltage curves and current-voltage waveforms, the images demonstrating the discharge development and propagation are also recorded. Presented results reveal that secondary electrons play an essential role in sustaining the discharge in microgaps, where the relationship between breakdown voltage and gap spacing is far away from the standard scaling law at atmospheric pressure.