Cathode and plasma phenomena in vacuum-arc sources of deuterium ions

An experimental and theoretical study of the content of deuterium ions in the arc discharge plasma was performed for deuterated zirconium cathodes. It was found experimentally that in a high-current arc mode with a current pulse duration of several microseconds and an arc current amplitude of more than 600 A, the content of deuterium ions in the plasma can reach more than 80%, which is twice that in the cathode material. An increase in the deuterium ion content in the plasma is accompanied by an increase in the average charge of zirconium ions. Models are proposed to describe the deuterium desorption from the cathode surface and the ionization processes in the plasma of a deuterated cathode arc. The models are based on the idea that the cathode spot of a vacuum arc has a cellular (ecton) structure. The calculations performed using these models have shown that the best conditions for increasing the deuterium ion content in the arc plasma occur in the initial stage of the arc discharge. In this case, the cells of the cathode spot are located in close proximity to each other and the deuterium desorbed not only directly from the zone of operation of the spot cells but also from the hot regions of the cathode adjacent to this zone.