A collisional-radiative model applicable to argon discharge over a wide range of conditions. IV. Application to inductively coupled plasmas

Abstract

For pt.III see ibid., vol.23, p.526 (1990). The extensive collisional-radiative model is applied to plasmas generated by a RF coil in an atmospheric argon flow in order to investigate excitation mechanisms and departures from local thermodynamic equilibrium in several spatial positions in these discharges. Computations are carried out for various sets of input parameters, such as the electron kinetic temperature Te, the atom temperature Ta, the electron number density ne, the ground-state atom population n1, the plasma column radius R and the escape factors Lambda mn and Lambda m, characterizing the non-equilibrium plasmas under consideration. The numerical modelling presented yields reliable information on the populations in the excited levels and on the validity of the so-called 'close to LTE concept' and the occurrence of an ionizing or a recombining regime in the locations investigated. The effect of the changes in the discharge parameters Te, Ta, ne, R and Lambda 1n on the excitation mechanisms, together with the role played by the inelastic atom-atom collisions and by the recombination flow of electrons from a continuum, are also shown.

Optical Emission Spectroscopic (OES) analysis for diagnostics of electron density and temperature in non-equilibrium argon plasma based on collisional-radiative model

“…(i) excitation and deexcitation by electron collisions with an atom in the level q 1 (q 1 ≠ p), (ii) population by radiative decay from the higher level q 2 (q 2 > p) and depopulation to the lower level q 3 (q 3 < p), (iii) ionization loss from the level p by electron collisions and its reversal process, three-body recombination, to the level p, and (iv) radiative recombination to the level p. In short, the population and depopulation of the level p are described with the electron collision processes, (i) and (iii), and with the radiative processes, (ii) and (iv). In this respect, this excitation kinetic model is referred to as the Collisional-Radiative (CR) model [33][34][35][36][37][38][39][40][41][42][43]. Figure 1 schematically illustrates the population/depopulation kinetics described with the CR model.…”

“…For the atmospheric-pressure plasmas, atomic collisions, i.e. so-called 'quenching processes', must be included in the excitation kinetic processes [40][41][42][43][44][45]. Hereafter, to make the CR model possible to treat the atmospheric-pressure discharge, the collisional excitation and deexcitation with the ground-state atom are included into the present CR model.…”

“…When the relationship between the excited-state populations and the plasma parameters is described, an excitation kinetic model is frequently applied, which is referred to as the 'Collisional Radiative model' (CR model) and will be detailed in the next section [33][34][35][36][37][38]. Owing to economical and historical backgrounds, argon is usually chosen as a mother discharge gas species in most of the plasma processes, and consequently, the argon CR model becomes necessary where the excitation kinetics of argon is well modeled in terms of rate equations to describe time evolutions of number densities of excited states [40][41][42][43][44][45]. In this application, the input and the output of the CR model become reversal.…”

Spectroscopic Measurement of Electron Temperature and Density in an Argon Plasma Jet Based on Collisional-Radiative Model

“…The CR model has been developed by Vlček [14], and its applicability to various plasmas has been confirmed by Vlček and Pelikán [15]. The outline of the CR model is as follows: In the CR model, Ar atom has 65 effective levels.…”

“…It is important to consider the opacity effect since the radius of plasma is large enough to trap radiation. An effect of radiation trapping in the CR model is considered for radiative transitions to the ground state of Ar atom by using optical escape factor implemented by Vlček [14,15]. Re-absorption of radiation caused by transitions between excited states is neglected because the plasma is assumed to ).…”