Angular distribution of ion current in a vacuum arc with a refractory anode

The total ion current and its angular distribution were measured in the radially expanded plasma of a hot refractory anode vacuum arc (HRAVA). The ion current increased during the transition from the initial cathodic arc stage to the developed HRAVA stage. The total ion current in the HRAVA was found to be significantly higher (up to 50%) than that found in the conventional cathodic arc. On the initial cathodic arc stage the ion current angular distribution peak was shifted from the gap mid-plane to the anode direction due to the contribution of the cathode plasma jets. In contrast, in the developed HRAVA stage and with small gaps (<6 mm) ion current angular distribution was symmetric with respect to the gap mid-plane due to dissipation of the cathode jets in the dense inter-electrode plasma of the anode plume. With large gaps (>20 mm), the developed HRAVA stage was more stable than the initial cathodic arc stage, due to the increased plasma density in the gap.