Impact of cathode evaporation on a free-burning arc

Summary form only given, as follows. In the center of a free-burning, high-intensity argon arc at atmospheric pressure, a highly ionized vapor beam of copper has been generated by a continuous feeding of a thin (0.5- and 1-mm-diameter) copper wire to the hot surface region of the cathode in the vicinity of the plasma attachment. The copper vapor is carried into the plasma column between the electrodes by the self-magnetic induced plasma flow caused by the conical shape of the cathode. In order to study the vapor beam, the arc was modeled at atmospheric pressure, with a current of 150 A, a gap spacing of 1 cm, a cathode tip of 60°, and a copper vapor flow of 1 mg/s. The temperature, mass flow, current flow, and Cu concentration were calculated for the entire plasma region. The intensity distribution of the CuI spectral line at 5218.2 angstrom was also recorded by emission spectroscopy and compared with the calculated values. The copper vapor in the cathode region has velocities of 210 m/s with a mass concentration of above 90% within 0.5 mm from the arc axis. The vapor passes from the cathode toward the anode with a slight diffusion in the argon plasma. Higher temperatures and current densities in the core of the arc, caused by the cathode evaporation, were found.