Rep-rate modulator and electron gun for high power microwave research using ferroelectric cathodes

Abstract

Summary form only given, as follows. A novel pulse modulator, previously described at the 1995 PAC meeting, has been reconfigured to give a better pulse shape at a slightly lower beam energy and with a higher current (500 kV, 1000 A). The device has been run at rated voltage and current for pulse durations in excess of 200 ns and at a low /spl sim/0.1 Hz power supply limited repetition rate. The modulator, which is designed for use in our high power microwave research program, has been coupled to an electron gun which uses a ferroelectric cathode. We report in this paper on the revised design and performance of the modulator and present data on the electron gun design and characteristics. The recessed ferroelectric cathode is located in the fringing field of a 3 kG solenoidal magnetic field so that the 500 A emitted current is compressed to about a 1 cm diameter pencil beam. The cathode emission is initiated by a 100 ns 2 kV pulse inductively decoupled from the ground by a coaxial cable wound around the transformer core. The pulse transformer, which is driven by three pairs of 10 /spl Omega/ pulse transformer, which is lines in parallel, feeds a fourteen to one step up transformer giving a source impedance of 500/spl omega/. It is switched independently of the ferroelectric trigger to provide maximum flexibility in the design. Results will be reported on all aspects of the system design and operation.