Mode control and frequency tuning in a planar magnetically insulated transmission line oscillator with a slotted slow-wave structure

A slotted X-band planar magnetically insulated transmission line oscillator (MILO) operating with a moderate external magnetic field is proposed for wideband and high-power microwave (HPM) generation. To enhance the output power, the widths of the slow-wave structure (SWS) and cathode are increased. To suppress the accompanying higher-order mode competition, a pair of slots is incorporated into the SWS, which interrupts transverse wall currents and selectively couples out competing modes with minimal perturbation to the desired operating mode. Particle-in-cell simulations show that, under a 0.25 T external magnetic field, the slotted planar MILO can be tuned from 8.52 to 10.66 GHz by reducing the SWS depth from 5.5 to 3.5 mm, a modification readily achievable in the planar geometry. Over this tuning range, the output power decreases from 5.4 to 2.6 GW, corresponding to a beam-wave conversion efficiency from 46% to 20%. These results indicate that the proposed slotted planar MILO is a promising candidate for wideband, high-power, high-efficiency, and lightweight HPM sources.