Pulsed- and DC-Charged PCSS-Based Trigger Generators

Prior to this research, we have developed high-gain GaAs photoconductive semiconductor switches (PCSSs) to trigger 50-300 kV high-voltage switches (HVSs). We have demonstrated that PCSSs can trigger a variety of pulsed-power switches operating at 50-300 kV by locating the trigger generator (TG) directly at the HVS. This was demonstrated for two types of dc-charged trigatrons and two types of field distortion midplane switches, including a ±100 kVDC switch produced by the High Current Electronics Institute used in the linear transformer driver. The lowest rms jitter obtained from triggering an HVS with a PCSS was 100 ps from a 300 kV pulse-charged trigatron. PCSSs are the key component in these independently timed fiber-optically controlled low jitter TGs for HVSs. TGs are critical subsystems for reliable and efficient pulsed-power facilities because they control the timing synchronization and amplitude variation of multiple pulse-forming lines that combine to produce the total system output. Future facility-scale pulsed-power systems are even more dependent on triggering, as they are composed of many more triggered HVSs, and they produce shaped pulses by independent timing of the HVSs. As pulsed-power systems become more complex, the complexity of the associated trigger systems also increases. One of the means to reduce this complexity is to allow the trigger system to be charged directly from the voltage appearing across the HVS. However, for slow or dc-charged pulsed-power systems, this can be particularly challenging as the dc hold-off of the PCSS dramatically declines. This paper presents results that are seeking to address HVS performance requirements over large operating ranges by triggering using a pulsed-charged PCSS-based TG. Switch operating conditions that are as low as 45% of the self-break were achieved. A dc-charged PCSS-based TG is also introduced and demonstrated over a 39-61 kV operating range. DC-charged PCSS allows the TG to be directly charged from slow or dc-charged pulsed-power systems. GaAs and neutron-irradiated GaAs (n-GaAs) PCSSs were used to investigate the dc-charged operation.