Axial electron density and wave power distributions along a plasma column sustained by the propagation of a surface microwave

Abstract

The propagation of electron surface waves can be used to sustain long plasma columns. The relation between the axial distribution of the electron density observed along the plasma column and the corresponding power distribution of the surface wave that produces it is investigated. It is found that the electron density decreases almost linearly along the plasma column in the direction of the wave propagation. This is explained by assuming that the number of electrons produced over a given axial length is proportional to the wave power absorbed over that same length.

Travelling-wave-sustained discharges

“…E.g., the condition n const. [15,94], which holds for the dispersion behaviour of the SWs-within the thin-cylinder approach p R>1, v R>1-in weakly collisional plasma waveguides, results in a linear axial profile of the plasma density; here p = [k 2 − ( 2 ε p /c 2 )] 1/2 and v = [k 2 − ( 2 /c 2 )] 1/2 are the quantities which describe the radial variations of the wave field components, respectively, in the plasma-and in the vacuum-regions of the waveguide. Small values of the parameter = R/c provide conditions for the validity of n const.…”

“…Looking for this relationship has always marked the research on the TWSDs. The analysis of the wave energy balance in the very early studies on the discharges [94][95][96] led to the remarkable formula for the axial gradient of the-averaged over the discharge cross section-plasma density in the TWSDs…”

Experimental investigation of surface wave propagation in collisional plasma columns

“…[1][2][3] For the physical description of these discharges, the dispersion properties of the wave maintaining the discharge have to be known. [4][5][6][7][8][9] On considering the literature, one can note that the theoretical modeling of surface wave propagation is well developed in the limits of the collisionless approach (ӷ eff , and eff being the wave angular frequency and the effective collision frequency for momentum transfer͒. 4,5,8,10,11 There have been numerous investigations either assuming a radially homogeneous electron density distribution or including a radial density profile.…”

“…[4][5][6][7][8][9] On considering the literature, one can note that the theoretical modeling of surface wave propagation is well developed in the limits of the collisionless approach (ӷ eff , and eff being the wave angular frequency and the effective collision frequency for momentum transfer͒. 4,5,8,10,11 There have been numerous investigations either assuming a radially homogeneous electron density distribution or including a radial density profile. 4,5,[8][9][10]12 The collisional effects on wave propagation have been considered mainly with respect to discharges operating at atmospheric or intermediate pressures, i.e., for strongly collisional plasmas ( eff /Ͼ1).…”

Axial structure of plasma column sustained by non‐symmetric electromagnetic surface wave

“…There are some common approaches in theoretical description of such discharges which differently simplify the problem [2]. Current study was carried out in the framework of electrodynamic approach that consists in detailed analysis of SW characteristics (phase characteristic, attenuation coefficient, wave energy transport) while plasma elementary processes are taken into account only in simplified manner [5,6,7,8]. The experimental data show [9] that axial distribution of plasma density in gas discharges sustained by symmetric (m = 0) and dipolar (m = ±1) SW is well described by means of theoretical models based on the electrodynamic approach [5].…”