Effect of slow wave structure length on microwave emission from a high-power backward-wave oscillator

Summary form only given. Effect of slow wave structure length on microwave emission from a backward-wave oscillator (BWO) with an intense relativistic electron beam was studied experimentally. The slow wave structure of a circular waveguide with square-wave wall of 57 periods maximum is constructed from individual rings for each period, then its length can be easily changed in any period. The inner and outer radii of the waveguide structure are 1.4 cm and 2.0 cm, respectively. The length of each ring, or one period, is fixed in 0.9 cm, while the length of inner radius section can be exchanged in different length. An annular electron beam with the energy of 300 kV, current of 2 kA, duration of 50 ns, and outer radius of 0.8 cm propagates in the axial magnetic field of 1.5 kG.