Development of a Li− ion source

Sources of Li− ions are needed for diagnostic neutral beams for fusion research. Previous efforts to generate Li− beams have focused on electron capture in a gas or production on a low work-function surface in a plasma. Volume production of Li− by dissociative attachment of optically pumped lithium molecules has also been studied. This paper presents experimental results for volume production of a Li− ion beam from a plasma discharge. These results show that a discharge source of Li− ions can provide suitable current densities for diagnostic beams. A theoretical model for the formation of Li− ions from Li2 molecules in the lithium discharge is developed. The model is in good agreement with the experimental results and shows favorable parameter scalings for further improvement of the Li− ion source.