Formation of the radio frequency sheath of plasma with Cairns–Tsallis electron velocity distribution

Abstract

The effect of the non-Maxwellian plasma with enhanced electron tails on the properties of the radio frequency (RF) sheath is studied with a one-dimensional collisionless model, which consists of the sheath model and the equivalent circuit model. In the sheath model, electrons are assumed to obey the Cairns–Tsallis distribution. For various entropic indices q characterizing the degree of electron nonextensivity and parameter α measuring the electron nonthermality state, the electron nonextensivity and nonthermality are found to modify the potential drop across the sheath and the sheath thickness, as well as the spatiotemporal variations of the potential, the ion and electron densities inside the sheath. With the decrease in q and the increase in α, the potential drop across the sheath and the thickness increase at any time in a RF cycle as a result of the increase in superthermal electrons in the non-Maxwellian tail. The dependence of the potential drop across the sheath on q and α is deeply related to the frequency and amplitude of the disturbance current. When the electron nonextensivity and nonthermality are strengthened, the enhancement of the sheath potential drop can cause a significant increase in the ion bombardment energy on the wall, sheath power dissipation, and plasma energy flux to the wall.

Numerical investigation of a radio frequency sheath with supra-thermal electrons in the presence of the magnetic field

“…The following typical parameters at EAST-like tokamak during ICRF wave heating are used in this paper [21]:…”

“…The change of the sheath structure caused by supra-thermal electrons can affect the dynamics and charging process of the dust grains in the sheath, current-voltage characteristics, ion bombardment energy and plasma energy flux to the wall. In an unmagnetized RF sheath, it is shown that the supra-thermal electrons can enhance the sheath potential drop at any time [9,20,21]and the resultant effect of the IED [9]. In some plasma fields such as laboratory and fusion plasmas, the magnetized RF sheath with non-Maxwellian electrons may be formed, and the shape of the IED depends very likely on both the magnetic field and supra-thermal electrons because it has been confirmed from the static sheath that the sheath structure can be modified by the interplay of the supra-thermal particles and magnetic field [15,16].…”

Landau damping of ion‐acoustic waves with simultaneous effects of non‐extensivity and non‐thermality in the presence of hybrid Cairns‐Tsallis distributed electrons

“…[35] From 2012 to 2020, various studies have been presented by using this hybrid distribution for linear and non-linear plasmas given in the Refs. [36][37][38][39][40][41][42][43][44][45] Recently, IAWs have been studied in Vasyliunas-Cairns distributed plasmas with two non-thermal parameters (𝜅, 𝛼). [46] The purpose of this paper is to explore the unique features of IAWs by using the kinetic theory approach in non-thermal hybrid plasmas with Cairns-Tsallis distributed (CTD) electrons.…”

Numerical and Analytical Study of Electron Plasma Waves in Nonthermal Vasyliunas‐Cairns Distributed Plasmas

“…(1995) also introduced a nonthermal distribution function to model the populations of nonthermal or energetic electrons observed in space plasmas by Freja and Viking satellites (Bostrom, 1992; Dovner et al., 1994). There are a lot of theoretical considerations of nonthermalities in plasmas (Abid et al., 2016; Darian et al., 2019; El‐Taibany et al., 2018, 2019; Farooq et al., 2018; Guo & Mei, 2014; Ou & Men, 2020; Rajib et al., 2019). The presence of nonthermal populations of particles has also been investigated in the plasmas produced due to laser‐matter interaction (Futaana et al., 2003; Sarri et al., 2010).…”