Temperature measurements for high-current free-burning arcs in nitrogen

A Fowler-Milne technique using the relative intensity of the 746.8 nm N I line has been used to measure the plasma temperature of free-burning arcs in nitrogen at 1 atm pressure. Temperature profiles are presented for different arc currents. The maximum plasma temperature depends on the arc current and is 27000 K near the tip of a 3.2 mm diameter thoriated tungsten cathode with a 60 degrees cone angle for a 200 A, 5 mm long arc. Comparisons are made between high-current arcs burning in argon and in nitrogen.