Impact of anode evaporation on the anode region of a high intensity argon arc

Temperatures in a free-burning, high intensity arc have been measured spectroscopically while the anode is kept either in a molten or solidified state. A comparison of the temperatures measured below the cathode for both cases shows that vapor is not penetrating into the cathode region and, therefore, evaporation of anode material does not influence the immidiate vicinity of the cathode. The distribution of the line emission coefficients of copper also revealed that there is no trace of copper vapor in the core of the arc up to 0.5mm from the anode. The temperature measurements 1 mm above the anode indicated an overall drop of the temperature in the anode region which, in turn, is associated with a drop in current density in this region (flattening of the current density profile). Increased electrical conductivity in the arc fringes due to ionization of the Cu vapor is consistent with this finding