Study of the properties of the asymmetric microwave low pressure gas discharge

Abstract

The properties of an asymmetric microwave gas discharge that occurs in an argon-filled resonator chamber of a processing plant near the surface of a metal product during the formation on it of a composite structure are experimentally and theoretically investigated. It is shown that with a significant difference between the electrode dimensions, the smaller of which is the product, and the larger are the resonator chamber walls, there is an area of a high energy density of the microwave field near the surface of the product, in which electrons are accelerated to high energies up to hundreds of eV. Diffusing from this area, high-energy electrons are decelerated due to inelastic scattering on the gas molecules that fill the resonator chamber, ionizing them or promoting them to an excited state. We have obtained a differential equation and found its solution which describes the diffusion process accompanied by the loss of energy by high-energy electrons, within the framework of the continuous deceleration model. The estimates of the main physical parameters characterizing the microwave gas discharge plasma are found. The conditions that are most favorable for the energy transfer from the microwave field to the plasma electron subsystem and the product surface treatment are determined.

A study of anode area physical parameters of asymmetric combined gas discharge

“…This section is an outline of the spatial structure of an asymmetric low-pressure microwave gas discharge ( Figure 2 ) (for details, see [ 27 , 28 , 29 ]).

Figure 2 1 – product, 2 – near-surface layer, 3 – electron acceleration zone, 4 – electron deceleration zone, 5 – ambipolar diffusion zone, 6 – cathode layer, 7 – chamber.

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“…Inside surface layer-2, a negative potential drop between the product and the plasma occurs [ 32 , 33 ]. On the outside, the electron acceleration zone – 3 borders on the deceleration zone – 4 which, in turn, consists of thinner layers of yellow, orange and red colors, inside which energetic electrons lose their energy as a result of elastic and inelastic collisions with argon atoms [ 28 ]. Between the deceleration zone and the cathode layer there is a dark zone of ambipolar diffusion – 5 where electrons together with ions diffuse to the resonator chamber walls.…”

“…This section is an outline of the spatial structure of an asymmetric low-pressure microwave gas discharge (Figure 2) (for details, see [27,28,29]).…”

“…The effect of a low-temperature plasma of asymmetric combined low-pressure gas discharge on a processed metal surface in a technological unit developed by the authors was previously studied experimentally and theoretically in [ 27 , 28 , 29 ]. It has been shown that it leads to a significant change in surface properties: an average 1.5 fold strength increase in microhardness parameter.…”

“…The first three of the above can be attributed to the anode region. The physical processes in the electron deceleration zone have been investigated in detail in [ 28 ]. In this regard, the purpose of this work is theoretical and experimental study in order to determine the parameters of the electron acceleration zone and the near-surface layer, as well as to assess their impact on the surface layer physical and mechanical parameter formation.…”