A collisional-radiative model applicable to argon discharges over a wide range of conditions. II. Application to low-pressure, hollow-cathode arc and low-pressure glow discharges

Abstract

For pt.I see ibid., vol.22, p.623 (1989). The extensive collisional-radiative model for an argon atom plasma is applied to a low-pressure, hollow-cathode arc discharge and to the positive column of a low-pressure glow discharge in order to clarify the mechanisms by which the excited levels in these discharges are populated, the results being compared with experimental investigations in the literature. Computations are carried out for various sets of input parameters, such as the electron kinetic temperature Te, the atom temperature Ta, the ion temperature Ti, 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, characterising the non-equilibrium plasmas under consideration. The predictions of the authors' model. i.e the populations in the excited levels as a function of the electron number density, the effective principal quantum number and the discharge current, are compared with the experimental results and in two cases also with the theoretical results of other authors. It is shown that all calculated dependences are fairly close to the corresponding experimental curves referring to both discharges. The results presented confirm the applicability of the so-called 'analytical top model' of van der Mullen et al. (1978, 1980) and Walsh's formula for Lambda 1n interpreted according to Mills and Hieftje (1984).

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.…”

“…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.…”

Characteristics of temporal evolution of particle density and electron temperature in helicon discharge

“…In these plasmas, a collisional-radiative (CR) model taking into account all relevant excitation and deexcitation processes is required. Vlček et al [36,37] have done excellent work on the CR model of argon, although it accounts too much for the collision and is too time-consuming for plasma diagnosis. In this work, we adopt a modified CR model following Clarenbach's method [6], in which the collisions between the excited argon atoms are ignored due to the low gas pressure.…”

Diagnostics of Helium-Argon Arc Discharge Plasma Based on Spectral Line Shape Measurements

“…However, such models available in literature cannot be directly applied to our plasma, because they are valid for pure argon plasmas only -see for example Refs. [32][33][34][35]. Therefore, the temperatures evaluated by applying the Saha equation have to be regarded as the ones determining the lower limit for the electron temperature.…”