Design and Experimental Study of a Dual Vircator Microwave Source
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The research described in this thesis details the design, construction, and experimental results in developing a virtual cathode oscillator (vircator) high power microwave (HPM) source. The HPM source utilizes two independent vircators to create simultaneous microwave signals whose frequencies are variable from approximately 1 GHz to 3 GHz. The vircators are powered by a pulsed power modulator. The modulator consists of a thyratron-switched capacitor bank that pulse charges a water transmission line through a pulse transformer. An output pulse is created by a pressurized oil switch with an output risetime of 20 ns. The capacitor bank is charged to 30 kV by a bank of power supplies. A 1:10 pulse transformer charges the water line to 300 kV in approximately 2.5 s. The output pulse from the water line is stepped up to 250 kV by an inductive adder. This signal is utilized to simultaneously drive the two, 32 Ω vircators in parallel with a 70 ns long pulse. Experimental results were collected for both the pulsed power system as well as the dual vircator HPM source. The vircators were characterized individually first to analyze the tunability of the sources. They were then connected in parallel to show frequency independence in order to create tunable multi-frequency HPM pulses.