Cathode and plasma phenomena in vacuum-arc sources of hydrogen isotope ions: I. Desorption of hydrogen isotopes during the operation of vacuum arc cathode spots

A model is proposed to describe the desorption of deuterium from a deuterated cathode during the operation of the vacuum arc cathode spot. The model treats a cathode spot as consisting of individual cells and involves a numerical simulation of the temperature fields that arise during the hydrodynamic processes responsible for the formation of microcraters on the cathode surface. Using a deuterated ZrD0.67 cathode as an example, it is shown that the amount of deuterium desorbed immediately from the crater formed during the operation of the cathode spot cells is several times smaller than the total amount of desorbed deuterium. The main portion of deuterium is desorbed from the hot cathode region adjacent to the crater and from the crater at the stage of its cooling. For a deuterated ZrD0.67 cathode, the percentage of desorbed deuterium can reach 80% of the total number of evaporated atoms, and it can be even greater if the cathode spot cells operate in the immediate vicinity of each other.