Plasma formation during solid-body irradiation by microwaves and its application for localizing the energy input

Abstract

Problems associated with the thresholds for plasma production (and connected with it, the nonlinearity of microwave energy release) during irradiation of complex metal - dielectric targets by microwaves in a deep vacuum or in a high-pressure gas were studied. The discovered effect of the low threshold for plasma formation, for which no adequate model exists, may find a number of applications, in particular, in quasi-stationary current generation, gas-discharge rocket engines and microwave soldering.

Non-self-sustained microwave discharge and the concept of a microwave air jet engine

“…The results of this paper, along with results of the previous paper [14] testify to the feasibility of the scheme based on surface non-self-sustained discharge shown in figure 2.…”

“…The microwave energy release is accompanied by efficient and rapid gas heating. Two direct consequences of this effect are the target heating [14] and the mechanical recoil momentum acquired by the target.…”

“…As figure 2 suggests, the microwave beam energy can be liberated locally near a specially prepared target in a gas at a high (up to atmospheric) pressure. As proposed and implemented in [14], non-selfsustained discharges of this kind can be used to heat narrow dielectric surface layers by heat transferred from the NSND region into the solid body. Here, however, we consider another effect.…”

Polyphase (non-resonant) multipactor in rectangular waveguides

“…Recent studies (see, e.g. [25][26][27]) have shown that the contact surface between a metal and a dielectric has a very low threshold for excitation of sparks (micro-plasmas) in microwave fields, and the probability of sparking depends only weakly on gas pressure. This plasma production mechanism may explain why low electron currents in the waveguide exist even at the maximum microwave powers attainable in the device and why the electron background current exists even when the wall surface is coated with soot.…”

Experimental and numerical investigation of multipactor discharges in a coaxial waveguide

“…The right (edge) waveguide section was held at atmospheric pressure and equipped with the matched load 5 to realize the regime of a travelling electromagnetic wave in all sections of the coaxial line and to keep the power reflection coefficient very low (less than 0.25%). To reduce the possibility of the appearance of microsparks at the metal-dielectric interface [30,31], the windows were positioned in the widest portion of the coaxial waveguide, where the microwave electric field is the weakest. Furthermore, to reduce the density of the plasma that can result from the microsparks, the joint between the window and the inner electrode was sealed by a narrow circular groove.…”