Wakefield excitation by a powerful sub-nanosecond 28.6 GHz microwave pulse propagating in a plasma filled waveguide

High-power microwave pulse generation (∼1.2 GW, ∼0.4 ns, 28.6 GHz) by a super-radiant backward wave oscillator (SR-BWO) and the feasibility of wakefield-excitation with this pulse in a plasma-filled waveguide are presented. The SR-BWO is driven by an electron beam (∼280 keV, ∼1.5 kA, ∼5 ns) generated in a magnetically insulated foilless diode and propagating through a slow-wave structure in a guiding magnetic field of 8 T. The plasma produced by an array of flashboards filling a cylindrical wire-array waveguide attached at the exit of the SR-BWO is also characterized. 1D and 3D numerical simulations demonstrate that for the experimental parameters of the microwave pulse and the flashboard plasma filling the waveguide, a wakefield forms accompanied by significant periodic density modulations such that their radial location and depth can be controlled by the waveguide radius, plasma density, and microwave power.