Design of a Nanosecond High Voltage Surface Discharge Switch

In this paper, we propose a concept for a novel high voltage low impedance surface discharge switch. The mechanism of surface discharges in gas was investigated on the nanosecond scale by Mesyats (2005). The important parameters which determine the switching performance of a pulsed-charged surface discharge switch, namely breakdown voltage, breakdown jitter and multi-channelling behaviour are controlled by dimensions of the discharge gap, the characteristics of the dielectric, the type and pressure of the gas and the rise time of the applied voltage pulse. The number of channels formed in a surface discharge switch is mainly a function of the applied voltage pulse (dV/dt > 1 kV/ns⁾². The breakdown mechanism of a surface discharge switch was investigated by Reinovsky and Goforth (2004). A novel design of high voltage low impedance surface discharge switch was simulated in CST Microwave Studio. The basic design parameters were 2 nanosecond pulse length, very low characteristics impedance (2 Omega) and 1 nanosecond rise time. A high dielectric constant causes a low impedance, while keeping the distance between the powered electrode and the grounded base plate large enough to prevent breakdown. The switch has been constructed and the first results of the experiments will be presented.