The Non-Linear High-Power Microwave Complete Absorption Phenomenon in a Plasma Filled Waveguide

We present the first experimental observation of a fully-absorption of a K-band high-power microwave (HPM) pulse (1.2 GW, 0.5 ns, 25.6 GHz) 1 in a plasma-filled waveguide. The plasma density dependent waveguide cut-off frequency is near to the pulse frequency. In the plasma-filled waveguide, due to the ponderomotive force created by HPM pulse, electrons in plasma being pushed towards the waveguide wall, form a potential well in the waveguide where the remaining electrons oscillate in the HPM pulse field. At this near critical plasma density, the group velocity of the pulse decreases, it provides sufficient time for these trapped electrons to collide with ions while their regular field-induced oscillation motion becomes chaotic and thermal. This results in all the energy of the pulse being transferred to the kinetic energy of electrons. This complete absorption phenomenon of HPM pulse is absent when pulse power is low and the potential well does not form in the waveguide. The experimental result is confirmed by particle-in-cell (PIC) simulations.