Effects of using a nonuniform-amplitude slow wave structure in a repetitively-pulsed, high power relativistic backward wave oscillator

The University of New Mexico Pulsed Power and Plasma Science Laboratory is conducting a systematic investigation of nonuniform-amplitude backward wave oscillators (BWOs) using the SINUS-6, a high power relativistic repetitively-pulsed electron beam accelerator The Sinus-6 produces a 12 ns microwave pulse with a peak power of 600 MW at 9.6 GHz. Efficiencies of microwave generation using both uniform and nonuniformamplitude BWOs are measured and compared with TWOQUICK (MAGIC) computer simulations. Each BWO structure is tested hundreds of times over a wide range of input parameters. The plentiful data allow for careful comparisons with theoretical models. Initial results confirm that prebunching the electron beam in a nonoscillating shallow ripple section results in increased microwave generation efficiency. Finally, experimental results from a high power serpentine mode converter based on a design of the Institute of Applied Physics, Nizhny Novgorod, Russia are also presented. The converter changes the dominant TM₀₁ mode output of the BWO to a TE_ll mode with very high conversion efficiency.