We present a plasma model for a new mode of a hot anode vacuum arc configuration. The arc runs between a copper cathode and a hot graphite anode separated by a 1 cm gap. The cathode operates in the multi-cathode-spot regime, while the hot graphite anode back-evaporates the material flux arriving from the cathode. The interelectrode plasma expands radially from the gap. Plasma electron temperature, plasma density, anode drop potential and anode temperature are calculated by solving a system of equations for the anode heat flux and for the effective anode voltage. Good agreement is found between calculated and measured parameters. For example, according to both the calculations and measurements during steady-state arc operation the effective anode voltage is /spl sim/6 V.

The hot refractory anode vacuum arc (HRAVA) is a plasma source where the source of the plasma flux is re-evaporation from the surface of a refractory anode of material originally emitted from the cathode. This plasma is used to deposit metallic films with small macroparticle contamination. Photographs of different stages of the development of the HRAVA are presented, allowing tracing of the details the development and giving characteristic times of the HRAVA development.

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 similar to130 degreesC for anode (2), and degrees100 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 are current. The deposition rate was about 1.5 times greater using asymmetric anode (2) than with a symmetric anode. (C) 2004 Elsevier B.V. All rights reserved.

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.

A two-dimensional (2-D) thermal model for cylindrical, graphite and molybdenum anodes in vacuum arcs is presented. The model includes heat flux from the plasma to anode surface, radiation from surfaces of the whole anode, and temperature-dependent thermophysical coefficients of the anode material. Arcs equipped with 3.2-cm in diameter and 1-3-cm-long anodes, with 175- and 340-A currents, and duration up to 250 s are analyzed. The results of the 2-D calculations indicate that the temperature of the active anode surface is distributed relatively uniformly, and the rate of anode temperature rise is larger for short (1 cm) anodes than for long (3 cm) anodes. Maximum active surface temperature depends-weakly on anode length. The rear surface temperature for a 3-cm anode length is lower for graphite anodes (1600 K) than for molybdenum (2100 K) when I = 175 A. The active surface temperature of both graphite (for 175-340 A) and molybdenum (for 175 A) and shorter (1 cm) anodes varies from 2000 to 2400 K, indicating that the vacuum arc can operate as a hot-refractory anode vacuum arc.