Emission spectroscopic studies of copper contamination in a free-burning argon arc

The vapor density distribution of copper contaminants evaporated from the water-cooled anode of an atmospheric-pressure free-burning arc (200 A and 1-cm gap spacing) was measured by emission spectroscopy. An automated emission spectroscopic setup has been developed in order to minimize the time for data acquisition and data evaluation. The vapor density distribution was measured in a two-step process. In the first step, the temperature distribution in the plasma was measured using the absolute line intensity method at the argon spectral line of 4300 angstrom. In the second step, the vapor density distribution of copper was determined by measuring the absolute intensity distribution of the copper spectral line at 5218 angstrom. The measurements show that the copper vapor is mainly concentrated in the fringes of the arc and in the center of the arc column with a radius of 1 mm. The vapor density distribution in the arc column is more concentric toward the cathode tip.