The calculation of electron density and temperature in Ar spectroscopic plasmas from continuum and line spectra

Abstract

The measurement of electron temperature and electron density from line and continuum radiation in Ar plasmas used for spectroscopic purposes is discussed. The correct equations for the calculation of these parameters from experimentally observable quantities are identified. Such expressions yield the theoretical spectral irradiance expected from line and continuum radiation. To aid calculations, grouped constants from these equations are calculated using SI units of measure. The sources of accurate values for the parameters and correction factors appearing in the irradiance equations are listed. In addition the approximations made in order to simplify electron temperature and electron density determinations are reviewed. Practical aspects of making accurate measurements of these parameters in Ar plasmas are considered. Theoretical plots of line to continuum emission ratio vs electron temperature and of continuum irradiance vs electron density are presented as an illustration using parameters appropriate for Ar emission at 430 nm and the spectrally adjacent continuum.