Radial excitation temperatures in argon-nitrogen inductively coupled plasmas

Abstract

Abel-inverted excitation temperatures are measured for Ar-N₂ inductively coupled plasmas (ICPs) formed in a conventional torch using a 27.12-MHz crystal-controlled generator. The dependence of temperature on gas composition (0–100% N₂ in the outer flow), forward power (1.2–3.0 kW), observation height (6 and 15 mm) and injector gas flow-rate (1 and 2 l min^–1) are studied using Fe as the thermometric species. When 5–10% N₂ is used in the outer gas flow instead of pure Ar, the axial temperature is approximately 1000 K greater than that of the commonly used Ar ICP. Substitution of Ar in the outer flow by pure N₂ reduces the axial temperature from 6200 to 4900 K at 1.2-kW forward power. At 2.5 kW, the Ar-N₂ plasma, with pure N₂ in the outer flow, exhibits a temperature of approximately 6200 K, similar to that of a 1.2-kW Ar ICP.