Wake excitation by a powerful microwave pulse and its evolution in a plasma-filled waveguide

Abstract

We present the results of an experimental, theoretical, and numerical study of short and long time wake, produced by a 0.6 ns, 0.5 GW, 9.6 GHz high power microwave (HPM) pulse propagating in a plasma-filled cylindrical waveguide. The perturbation of the plasma density caused by the ponderomotive force prevents not only the pulse from spreading due to dispersion, but also leads to pulse compression. The high power pulse leaves far behind it a long lived positively-charged plasma whose electrons oscillate in the Coulomb potential well and ionize the background neutral gas over several tens to hundreds of nanoseconds. This leads to long time light emission observed in the experiment. The density of this newly created plasma can exceed many-folds its initial value. The theoretical model shows that as a result of the wake excitation by the propagating HPM pulse, fast electrons are ejected and collected on the waveguide wall. These high energy electrons, pulse compression, and long time light emission are evidence of the wake formation. The results of the experiment, the analytical model, and the numerical simulations are in good agreement.