Fast Marx Generator For Directly Driving A Virtual Cathode Oscillator

This paper presents the design, development and testing of a fast, compact hybrid-type Marx generator which is suitable to directly drive a high-power microwave producing virtual cathode oscillator. The developed Marx generator has an open circuit voltage of 300 kV, a pulse width of 640 ns (FWHM) and a rise time of 200 ns. The fast rise time is achieved by reducing the inductance of the discharge path with the help of specially designed spark gaps. The Marx generator operates in open air now, but will soon be placed in a container with insulation that will help to charge the stage capacitors to their maximum voltage rating repeatedly; it will also help to reduce the rise time further by bringing the return path close thus reducing the inductance. The Marx generator has six stages, and all stages are charged to same polarity, with 1.8 kJ being stored at full charge. The operational characteristics, such as the impedance, inductance, current- delivering capacity, rise time, etc; of the developed Marx generator are determined experimentally. A detailed study on the effect of loading on the generator and its performance is also conducted. The overall size of the generator without its container is 0.8m in length, 0.45m in height and 0.35m in width.