Anode temperature distribution and coating characteristics in a Hot Refractory Anode Vacuum Arc with an asymmetric anode

The temperature distribution in an asymmetric graphite anode and deposited copper film characteristics in a Hot Refractory Anode Vacuum Arc (HRAVA) were measured. The material to be deposited originates from the cathode and is re-evaporated from the hot anode. The discharge was between a water-cooled copper cathode (diameter 30 mm) and a thermally isolated anode (diameter 32 mm) with arc currents I=120 - 225 A, gap distances of h=5 - 18 mm and arc durations up to 150 s. The front surface of the asymmetric anodes was inclined so that the maximal and minimal anode lengths (L1, L2) were: (1) (30, 25) and (2) (30, 20) mm, whereas the length of the symmetrical anode was 30 mm. The anode temperature was measured using thermocouple probes located near the front and rear surfaces. The steady-state temperature at the front and rear anode surfaces for all anode geometries increased approximately linearly with current. The surface temperature for asymmetric anodes was not symmetric and the difference in steady-state temperature measured by thermocouples on the surface near the anode length L1 and L2 was ∼ 130 C for anode (2), and ∼ 100 C for anode (1), when I=175 A and h=18 mm. The macroparticle (MP) contamination in thin films deposited on substrates facing the anode decreased with arc current. The deposition rate was about 1.5 times greater using asymmetric anode (2) than with a symmetric anode.