All solid state pulsed power source based on photoconductive switches: From module to generator

High power photoconductive semiconductor switches (PCSSs) are considered a promising device for compact, repetitive pulsed power generation due to their advantages over other switches, such as fast response time, negligible time jitter, precise synchronization, high repetition rate and optical electrical isolation. In the past several years, high power PCSSs have been investigated at Institute of Fluid Physics, CAEP. Photoconductivity tests have been performed at different bias voltages, laser wavelengths and energies. Several packaging methods for lateral and bulk PCSSs were investigated and peculiar photoconductivity of high power GaAs PCSSs was observed. By using laser spots to trigger the opposite side of electrodes for lateral PCSS, the damages to ohmic contact were alleviated. Current filaments image of GaAs PCSSs when triggered by laser spots with different patterns were obtained by ICCD camera and analyzed. As a key unit of stack Blumlein lines (SBL), ferroelectric ceramic solid state pulse forming lines (PFL) and glass-ceramic PELs were developed for both energy storage and pulse forming. Combining the ceramic PFLs and PCSSs, a SBL module with an output voltage of 20.2 kV and a current of 8.1 kA were developed. Based on developments of SBL modules, an all solid state pulsed power generator with twelve modules was constructed to drive the industrial cold cathode diodes with different cathode configurations for generating intense x-rays. The diode voltage of 220 kV and electron beam current of 1 kA were achieved, and x-ray with full-width-at-half-maximum (FWHM) of 40 ns was generated. This all solid state x-ray machine can be operated in the repetition rate of 1 kHz.