The effect of pressure on a plasma plume: temperature and electron density measurements

Measurements of temperature and electron number density measurements have been carried out on a plasma plume under various pressure conditions (p = 1-0.3 bar) using emission spectroscopy. The anode nozzle used does not generate a shock wave or an expansion-compression zone. Ar- (1%) is used as the plasma gas. Temperature values are obtained from various lines of neutral argon. Electron number densities are obtained from the Stark-effect broadening of the 486.1 nm H line and the continuum measurements. Measurements of temperature and density profiles reveal the general features of a low-pressure plasma jet, namely relatively low temperature and long heating zone of the expanded jet. The LTE criterion is satisfied at higher pressures ( bar). Deviations from ionization equilibrium occur at lower pressure. The variation of excited neutral argon and states has been studied for lower pressures. tends to be overpopulated compared with .