Marx generator triggering with photoconductive switches

Fast rising, high-voltage, low jitter trigger pulses have been in high demand for a variety of applications. A recent application required triggering a compact Marx generator with very low trigger jitter. The lateral gallium arsenide photoconductive semiconductor switch (PCSS) being developed at the Air Force Research Laboratory (AFRL) has been implemented in this application. PCSS technology is an attractive solution because of the very low trigger jitter, high voltage switching capability and inherent trigger isolation properties. The PCSS has been packaged into an integrated unit for triggering a Marx generator. The Photoconductive Trigger Generator (PTG-30) requires external 24 VDC, TTL trigger and pressurized insulating gas for operation. Performance characteristics of the PTG-30 are variable output voltage from 5 to 13 kV, in four discrete steps. At maximum output voltage, the pulse risetime is approximately 350 pS. The high-voltage output pulse has an average of 22 ps rms temporal switching jitter with respect to a fast-rising trigger signal. The PTG-30 incorporates all required support components internal to the unit, including: laser diode and driver assembly, solid state FET-based pulse modulator, high-voltage DC to DC converter, and a pulse forming line. The versatility of this unit also allows for direct connection to a variety of antennas and other loads. This paper will discuss the manufacture and performance characteristics of the PTG-30 as well as experimental results from triggering a coaxial Marx generator.