Microwave N2-Ar plasma torch

Abstract

This work investigates the spatial structure of a microwave plasma torch driven by an azimuthally symmetric surface wave operating in N2-Ar mixtures at atmospheric pressure. The main plasma and wave characteristics are obtained in the framework of a self-consistent 2D model that describes the entire spatial structure of this source, including the discharge zone, sustained by the field of the surface TM00 mode, and the post-discharge plasma. The set of equations considered to describe the plasma source include: Maxwell's equations; the dispersion equation of the surface mode; the rate balance equations for vibrationally excited states of electronic ground state molecules N2(X 1Σ+g,ν); the rate balance equations for the triplet N2(A3Σ+u,B3Πg,C 3Πu) and singlet N2(a'1 Σ-u,a 1Πg,w1Δ u, a"1Σ+u) electronic excited states of nitroge and the Ar(3p54s) and Ar(3p54p) excited states of Argon; the rate balance equations for N+,N+2,N +3,N+4,Ar+,Ar+2 ions and electrons; the rate balance equations for the ground state N(4S) and the metastable states N(2P, 2D) of nitrogen atoms; the gas thermal balance equation; and the equation of mass conservation for the fluid. Model calculations of the 2D spatial distributions of species of interest such as charged particles (electrons and positive ions), N2(X1Σ +g, ν) vibrationally excited molecules, N2(A3Σ +u) metastables and N(4S) ground state atoms are presented and discussed. © Published under licence by IOP Publishing Ltd.