An analysis of LTE effects in inductively coupled RF plasmas

Abstract

Spectroscopic measurements are carried out on inductively coupled radio-frequency (RF) argon plasma over the pressure range 120 to 760 Torr. The electron number density is obtained by two methods: Hbeta profile and the absolute intensity of the argon continuum. Number densities of excited argon levels are deduced from absolute line intensities. The electron density measured in the hottest zone of the plasma decreases from 1016 to 6*1015 cm-3 with the decrease of pressure from 760 to 120 Torr. Comparison between the different number densities shows that the atmospheric plasma is in local thermodynamic equilibrium (LTE) whereas weak departures from equilibrium are observed at pressures below 300 Torr.

Computational simulation of a particle-laden RF inductively coupled plasma with seeded potassium

“…There are some papers concerning the deviation of LTE especially under the low operating pressure or near wall in the coil region where the temperature gradient is steep in an RF-ICP [4,9,10]. The hypothesis of LTE or close-to-LTE is, however, considered to be valid for an RF-ICP operated at atmospheric pressure and at a coil frequency of a few MHz.…”

Effects of working pressure on temperature characteristics in multiphase AC arc

“…Second one is that the energy exchange between the electron and heavy particles should be sufficiently frequent. This is assumed to be satisfied at observed excitation temperature range of 6,000 to 12,000 K. The local thermal equilibrium is almost established at the working pressure above 40 kPa (Gravellet et al, 1989). Therefore, the measured argon excitation temperature can be treated as the gas temperature in the most region of the multiphase AC arc, except some specific region with steep temperature gradient such as the very close to the electrode (Tanaka et al, 2013b).…”

Prediction of extinguish boundary of radio frequency thermal plasma torch within carrier gas injector

“…The thermophysical properties and electrical conductivity of argon plasma gas are obtained in the approximation of local thermodynamic equilibrium (LTE) from calculated data [5,6], a discussion of the use of LTE conditions were made in [7][8][9][10]. Under atmospheric conditions, the plasma as a whole could be considered in LTE except at the moment of working modes changing.…”