High-Power G-Band Relativistic Surface-Wave Oscillator With 2D-Periodic Slow-Wave Structure of Planar Geometry

Comparative theoretical and experimental studies of G-band surface-wave oscillators (SWOs) with one-dimensional (1D) and two-dimensional (2D) planar slow-wave structures (SWSs) has been carried out. These oscillators have been driven by a sheet electron beam with a cross-section of 0.3 mm $\times 20$ mm formed by the SINUKI accelerator 650 keV / 1 kA / 17 ns. At the oversize factor of $\sim ~15$ (the ratio of the transverse size to the radiation wavelength), in the case of 1D SWS, a multistable generation with excitation of various transverse modes was observed, characterized by a jitter of the radiation frequency. In contrast, 2D SWS ensures a single-mode generation regime stable to variations of beam parameters. In accordance with the simulations, narrow-band generation with excitation of the fundamental mode of 2D SWS was observed in the experiment at an operating frequency of 160 GHz with an output power of 30 MW and an electron efficiency of 5%.