S. A. Dvinin

Surface microwave discharges in air

A microwave discharge excited on the outer surface of a dielectric antenna has been investigated. The transverse and longitudinal dimensions and propagation velocities of the discharge have been measured as functions of the air pressure and the power and duration of the exciting microwave pulse. The spatial distributions and time evolution of the gas temperature, electron density, and radiation intensity of the discharge have been determined. It is shown that the degree of ionization of the discharge plasma can exceed 10%. The spatial distribution of the electron density is found to depend strongly on the air pressure.

Mechanisms of microwave surface discharge propagation

A microwave discharge propagating over the surface of a dielectric antenna is studied. It is experimentally shown that the velocity of discharge propagation over the surface is maximal early in microwave pulse application and grows with the applied power. The breakdown wave defines the velocity of the discharge at its early stages (t = 1–3 μs). Ambipolar diffusion governs the discharge propagation at the stage of its evolution (t= 3–100 μs), and, finally, slow surface combustion is possible only at the stationary stage of the discharge (t > 100 μs). The electric field is localized in a thin (∼1 mm) surface layer. High values of the reduced electric field, E/n = 100–500 Td, provide efficient energy deposition to the plasma, i.e., favor the rapid heating of the gas and the efficient generation of charged particles. This makes the discharge promising for hypersonic aerodynamics.

On the theory of microwave discharges excited on the surface of a dielectric antenna

Microwave gas discharges excited near a dielectric surface are investigated. Such discharges can exist over a broad range of gas pressures and thereby can be used to solve a wide variety of applied problems. The wave dispersion properties favorable for discharge excitation are analyzed, and a kinetic discharge model is considered that can be used to calculate the discharge parameters. A model of a steady discharge at gas pressures of 102–104 Pa is constructed.

Simulation of a DC Discharge in a Transverse Supersonic Gas Flow

AbstractThis study is devoted to the investigation of a dc discharge in a transverse gas flow. It is shown that the discharge may exist in several forms depending on the gas flow velocity. The standard stationary discharge similar to a discharge in still gas is realized if the displacement rate of the plasma boundary exceeds the gas flow velocity. The displacement rate of the plasma boundary in a diffusion model is defined by the relation Vf = 2

Dynamics of a High-Frequency Streamer

\sqrt {D_a v_i }

Threshold fields for stimulated Brillouin scattering in spatially limited plasma

, where Da is the ambipolar diffusion coefficient, and νi is the frontal ionization frequency. Otherwise, the discharge assumes the form of two plasma wakes formed by the cathode and anode, respectively. The surface of the plasma wakes is oriented at an angle α to the flow velocity Cs (sinα = Vf/Cs). If sinα is smaller than the ratio of the discharge sustaining voltage in the stationary regime Ust to the breakdown voltage Ubk, the discharge transforms into the pulse–periodic form, when the formation of a structure of the cathode and anode plasma wakes is interrupted by a new gas breakdown. A numerical simulation of the discharge properties is performed. The numerical simulation results are compared to the experimental ones.

High-frequency surface waves at a plasma-metal interface: I. Linear model

The problem of the stimulated scattering of a two-dimensional localized pumping wave is considered. The dependence of the spatial gain on the angle of scattering and intensity of pumping is found. Interpretation of this gain is given at arbitrary relationships between the free path of the sound wave and transverse dimension of the interaction domain.

Kinetic theory of a gas-discharge positive column and wall sheath

The space-time evolution of small-size high-frequency plasmoids created by a high-frequency gas break-down around a solitary primary ionization centre is investigated. It is found analytically and by some computer simulation that a quasi-spherical plasmoid being formed at the first stage of the avalanche-like process in a course of time stretches in the direction of the external electric field and turns into a rapidly growing “high-frequency streamer”. This effect is due to an increase of the electric field amplitude at “polar” regions of the plasmoid.