Ionization-Induced Self-Channeling of an Ultrahigh-Power Subnanosecond Microwave Beam in a Neutral Gas.

Ionization-induced self-channeling of a ≤500 MW, 9.6 GHz, <1 ns microwave beam injected into air at ∼4.5×10^{3} Pa or He at ∼10^{3} Pa is experimentally demonstrated for the first time. The plasma, generated by the impact ionization of the gas driven by the microwave beam, has a radial density distribution reducing towards the beam axis, where the microwave field is highest, because the ionization rate is a decreasing function of the microwave amplitude. This forms a plasma channel which prevents the divergence of the microwave beam. The experimental data obtained using various diagnostic methods are in good agreement with the results of analytical calculations, as well as particle in cell Monte Carlo collisional modeling.

Stationary striations in plasma, created by a short microwave pulse in a waveguide filled with a neutral gas.

It was observed experimentally that after crossing a waveguide filled with a neutral gas a short powerful microwave pulse leaves a periodic glow of plasma along the waveguide, persisting for several tens of nanoseconds. A theoretical model is presented which in combination with numerical simulations proposes a possible explanation for this phenomenon.

Frequency conversion, "superluminal" propagation, and compression of a powerful microwave pulse in propagating ionization front.

Frequency up-conversion (∼10%) and compression (almost twofold) of a powerful (≤250 MW) microwave pulse in the propagating ionization front produced by the pulse itself in a gas-filled waveguide, is investigated experimentally and analyzed theoretically. Pulse envelope reshaping and group velocity increase manifest themselves in a propagation of the pulse faster than in the empty waveguide. A simple one-dimensional mathematical model allows the adequate interpretation of the experimental results.

Observation of magnetically induced transparency in a classical magnetized plasma.

We report the first demonstration of magnetically induced transmission in an opaque magnetized plasma. Magnetically induced transmission in a plasma is a classical analog to the electromagnetically induced transparency in atomic systems. The transmission of radiation through an axially magnetized plasma is obtained by applying an additional one dimensional transverse spatial periodic magnetic field. The transverse-periodic magnetic field uncouples the right-hand electromagnetic wave from interacting with plasma electrons, rendering the plasma band-stop transparent. This provides means to control the extent of absorption of electromagnetic radiation in magnetized plasma.