Spectroscopic Measurement of Temperatures in an Argon Plasma Arc

Temperature profiles across the Poiseuille plasma arc have been calculated from measured radiation intensities from the atmospheric argon plasma at arc currents from 1 to 400 A. The transition probabilities for several neutral argon lines were calculated from the measurements. The investigation shows the central core of the arc to be in local thermodynamic equilibrium but the sides of the arc to deviate from local thermodynamic equilibrium. The extent of this deviation was found to increase with decreasing current.