Spectroscopic diagnostics for a low-pressure plasma spray deposition system

Abstract

Emission spectroscopy was utilised to characterise an arc-driven d.c. plasma jet used for low-pressure plasma spray deposition. Line of sight argon emission line intensities were measured in the wavelength range from 400 to 850 nm; nitrogen rotational spectra were measured from 300 to 450 nm. The Ar⁰ excitation temperature was calculated using the Boltzmann slope method, assuming partial local thermodynamic equilibrium (LTE). The degree of over-population of some energy states was also calculated. Data showed that partial LTE did not exist; therefore, calculated temperatures represent Ar electronic state population distribution. Temperatures ranged from 4220 to 7870 K and varied with arc power, chamber pressure and spatial position.