Measurements of the molybdenum anode temperature in a hot refractory anode vacuum Arc

The temperature distribution in symmetric and asymmetric molybdenum anodes of a Hot Refractory Anode Vacuum Arc was determined using high temperature thermocouple probes placed in three locations in the anode body. Three different anode geometries Were used, with arc currents in the range 125 - 225 A, and electrode separations of 5-18 mm. The anode temperature increased with arc current and decreased with the electrode separation. The steady state anode surface temperature exceeded 2200-2300K for currents larger than 150A. Photographic study of the interelectrode region indicated that during the transition period to the Hot Anode mode the plasma plume was asymmetrically distributed on the asymmetric anode surface, resulting in an asymmetric anode surface temperature distribution.