Temperature Distribution Dependence on Refractory Anode Thickness in a Vacuum Arc: Experiment

The time-dependent anode temperature was measured in a hot refractory anode vacuum arc (HRAVA) sustained between a consumed water-cooled cylindrical Cu cathode and nonconsumed cylindrical W anodes with thicknesses of separated by gaps of 5, 10, 15, and 20 mm. Arc currents of were applied for periods up to 210 s. The anode temperature was measured using high-temperature thermocouples at different points in the anode body. The visual radiation emitted by the plasma plume was recorded with a digital camera. The anode temperature increased with time, reaching a steady-state value which slightly increased with arc current. The anode temperature decreased with the gap and was higher for thinner anodes. When was increased from 5 to 30 mm, the time for the anode front-surface temperature to reach the steady state increased from 45 to 140 s, while this temperature decreased from 2525 to 2325 K . Thus, minimizing advantageously minimizes the start-up transient when using the radially expanding HRAVA plasma plume for thin-film deposition.