A high voltage pulsed power system for repetitive vircator testing

The University of Missouri - Columbia (UMC) is beginning research into high power microwaves and their effects upon various systems. A high power microwave (HPM) laboratory is, therefore, being established at UMC to provide the capacity to perform the tests. The initial HPM source will be based on a virtual cathode oscillator, or vircator. The vircator requires a stable pulse-top voltage and will be required to be repetitively driven. The UMC has modified an existing repetitive pulse generator to achieve the required pulse characteristics. The UMC vircators will be driven by a water pulse forming line output whose output pulse is transformed to higher voltage by an induction voltage adder cell. The coaxial water pulse forming line (PFL) has an impedance of 4.8 Ω and produces a 150 kV pulse that is 70 ns in length into a matched-impedance load. A modulator has been developed to provide the requisite 365 J energy pulse at repetition frequencies up to 40 pps in continuous mode operation. The output voltage from the PFL is delivered to a matched-impedance transmission line and transformed to 300 kV by an induction voltage adder to provide sufficient voltage for the vircator to operate efficiently. Simulations of the driver connected to a vircator model were used to verify performance. Simulation results are discussed showing driver performance under rep-rate conditions.