Pulse shortening in a high power backward wave oscillator

Summary form only given. This paper describes an experimental and theoretical investigation specifically oriented to revealing the various physical phenomena responsible for pulse shortening in a high power backward wave oscillator (BWO). Pulse shortening is common among all long-pulse, electron beam-driven, high power microwave sources. Therefore, data obtained in the course of these investigations should be applicable to a variety of high power microwave sources. Experiments were conducted at the University of New Mexico (UNM) on the UNM Long-pulse BWO Experiment. Driving the experiment was a modified Physics International Pulserad 110 A electron beam accelerator, which can produce intense relativistic beams with energies ranging from 200-500 kV at currents of 1.5-4.0 kA and having pulse durations of 400-500 ns (FWHM). Microwave radiation was generated in the X band with maximum peak powers of at least 200 MW but with pulse widths of only 10´s of ns (FWHM). Longer pulse widths approaching 100 ns FWHM can be obtained but at lower powers. The paper presents the most recent experimental and theoretical results, as well as plans for future diagnostic development and theoretical investigation.