Non-thermal plasma instabilities induced by deformation of the electron energy distribution function

Abstract

Non-thermal plasma is a key component in gas lasers, microelectronics, medical applications, waste gas cleaners, ozone generators, plasma igniters, flame holders, flow control in high-speed aerodynamics and others. A specific feature of non-thermal plasma is its high sensitivity to variations in governing parameters (gas composition, pressure, pulse duration, E/N parameter). This sensitivity is due to complex deformations of the electron energy distribution function (EEDF) shape induced by variations in electric field strength, electron and ion number densities and gas excitation degree. Particular attention in this article is paid to mechanisms of instabilities based on non-linearity of plasma properties for specific conditions: gas composition, steady-state and decaying plasma produced by the electron beam, or by an electric current pulse. The following effects are analyzed: the negative differential electron conductivity; the absolute negative electron mobility; the stepwise changes of plasma properties induced by the EEDF bi-stability; thermo-current instability and the constriction of the glow discharge column in rare gases. Some of these effects were observed experimentally and some of them were theoretically predicted and still wait for experimental confirmation.

NUMERICAL CALCULATIONS OF THE ELECTRON ENERGY DISTRIBUTION FUNCTION IN (50% SF6 - 50 % Xe) MIXTURE WITH CORRESPONDING TRANSPORT PARAMETERS

“…This is true for the gas below the atmospheric pressure. Even all the curves in figure (6) show the same behavior; that is as the electron concentration increased the drift velocity become higher with constant E/N. This can be distinguish at lower E/N, while the curves of become closer at higher E/N indicating small effect.…”

“…In thermodynamic equilibrium the EEDF has a Maxwellian shape if the ionization degree is high because electronelectron collisions drive the distribution towards a Maxwellian [6]. However, in most of the plasmas the deviations from the Maxwellian shape take place.…”

Enhancing the Properties of Photocatalysts via Nonthermal Plasma Modification: Recent Advances, Treatment Variables, Mechanisms, and Perspectives

“…The catalytic performance of an NTP-treated photocatalyst is dictated by the applied condition of the plasma phase and the electronic property of the surface catalyst . Moreover, the plasma properties are extremely sensitive to the operating parameters.…”

“…Moreover, the plasma properties are extremely sensitive to the operating parameters. Mathematical modeling and theoretical modeling reveal that this sensitivity is attributed to complex changes in the electron energy distribution function (EEDF) caused by small changes in electric field intensity, the electrons and ion density, the gas excitation degree, and the secondary electron emission from the surfaces. − Therefore, balancing the variables, including incident ions, metastable particles and free radical fluxes, and the ion energy by regulating the discharge characteristics of plasma, and revealing the interaction mechanism between plasma active particles and surfaces is the key to realize the controllable induction of material surface defects. − In light of this consideration, three variables, which are feeding gases, plasma pressure, and electric power, will be discussed in detail, as they serve important roles during the NTP modifications.…”

“…In situ diagnostic techniques enable real-time monitoring of electron density, electron temperature, ion flux, and active species that are produced in the plasma during modification and reveal the mechanism of plasma–surface interaction. , Such information, when combined with product distribution, would be invaluable to optimize a catalyst surface with specific reactivity.…”