A 600-kV double-pulser for the PHERMEX electron gun

The PHERMEX Radiographic Facility is a 50-MHz, 3-cavity, RF-Linac driven by a pulsed, thermionic electron-gun injector. The PHERMEX is used to take flash radiographs using X-rays at a single time in an explosively driven event. To investigate the time evolution of these events requires two things: (1) a multiple-pulser to drive the electron-gun injector and (2) a large-format, gamma-ray camera system to record a scintillator at the different times. We report the success of developing a reliable double-pulser that consists of two Marx generators that independently charge two PFLs which are switched out at about 1.4 MV. The PFLs are connected in series by large diaphragm switches that are independently laser triggered by two quadrupled-YAG lasers. Tests of the system into a dummy load, produced two high quality 600 kV pulses separated by 1.0 /spl mu/s. Each pulse has a FWHM of 90 ns and a 50-ns flat-top /spl plusmn/3 % with rise- and fall-times of 25- and 35-ns, respectively. The interpulse time is variable up to about 275 /spl mu/s; the first switch is kept closed by a "keep alive" inductor. The system has produced a 50 shot sequence of two pulses with a 1-sigma jitter <1 ns. The system has been modeled using TOSCA-3D, FLUX-2D, and a transmission line model run with the circuit analysis code Micro-CAP.