Advances in long-pulse, high power vacuum BWO operation

Summary form only given, as follows. Long-pulse, high power microwave experiments are continuing at the University of New Mexico (UNM) using a Physics International Pulserad 110A that has been modified for long-pulse operation. The Pulserad 110A originally consisted of an 11-stage Marx bank (having an energy storage capacity of 2.75 kJ) followed by a Blumlein for pulse shaping. The Blumlein has been replaced now with a parallel L-C network, as described by Cummings, and together both the Marx bank and the L-C network form a type-A pulse forming network with an output impedance of 40 /spl Omega/, a pulse duration of 500/spl sim/700 ns, and a peak voltage and current for a matched load of 570 kV and 14.3 kA. Shunt resistors placed at the output have reduced the output current to /spl sim/7.5 kA and increased the output impedance to /spl sim/76 /spl Omega/. The UNM Pulserad 110A drives an electron beam diode having an annular, knife-edge graphite cathode. The electron beam which is emitted from the cathode enters a slow-wave structure (SWS) having 12 periods with varying ripple amplitudes. Beam current and cathode voltage are monitored with self-integrating Rogowski coils and a capacitive voltage divider, respectively.