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Description
A simple 1D model of the propagation of an ultra-short (≤ 1ns), TM01 mode, 28 GHz, ~1 GW, microwave pulse produced by an SRBWO (Super Radiant Backward Wave Oscillator) in a ~10$^{10}$ cm$^{-3}$ density plasma shows that a wakefield develops as a result of the radial ponderomotive and the Lorentz force. This is a scaled-down equivalent of a laser wakefield experiment with more manageable parameters. The model shows that for best results the waveguide radius needs to be such that the Lorentz and ponderomotive forces balance in a particular way. We simulate the system by the 3D PIC LSP code and confirm this model. Moreover, we simulate the experimental waveguide which has a slotted wall. These slots are required to be wide enough so that the plasma produced at larger radii penetrates the waveguide filling it uniformly, large enough to allow diagnostics, and sufficiently small, so that the microwave radiation is contained.
