The development of a one microsecond pulse length, repetitively pulsed, high power modulator and a long-pulse electron beam diode for the production of intense microwaves

This paper discusses the pulse power and explosive emission electron beam diode development effort we have undertaken to power a relativistic klystron amplifier (RKA) microwave source. The pulsed power and electron beam must enable the RKA to produce one kilojoule of 1.3 GHz radiation per pulse at a 5 Hz repetition frequency. These efforts include tests and improvements of a 1 μs pulse length thyratron switched modulator, and the computational and experimental design of a 1-μs-pulse-length explosive emission electron gun. The one microsecond pulse length is almost an order of magnitude beyond what has been achieved heretofore with an RKA. Achieving a peak power approaching 1 GW for 1 μs requires a well behaved electron beam on that time scale. An electron beam diode has been developed that delivers a peak current of 4 to 5 kA for a pulse duration exceeding 1 μs, at a beam kinetic energy above 600 keV. BANSHEE is the high voltage modulator designed for use as an electron beam driver for high power microwave tube development. The BANSHEE output pulse design parameters are 1 MV and 10 kA, with a 1 μs pulse width at a repetition rate of 3-5 Hz, driving a load of impedance of 100 ohms. BANSHEE is a thyratron-switched line-type modulator with a pulse transformer output stage. The modulator design is pushing the state of the art in thyratron technology and capacitor lifetime. The results of the BANSHEE modulator testing are described.