ABSTRACT
Negative-ion sources have been developed according to requirements from their application fields such as accelerators, fusion research, and material science. Several kinds of high-current hydrogen negative-ion sources, such as the magnetron, Penning, Ionization Gauge (PIG), multicusp, and duopigatron types, were developed. The negative-ion production mechanism is very similar to the magnetron type except its discharge mode, i.e., PIG discharge. The mechanism of negative-ion production was considered as a result of the reflection of positive hydrogen ions on the cesiated surface. Mueller and Hortig were the first to show that heavy negative ions were effectively produced on a cesiated metal surface by sputtering. Two potential sputter type negative-ion sources were developed: one was the universal negative-ion source by Middleton and the other was Aarhus negative-ion source by Andersen. A negative ion is produced through a collision between a positive ion and a neutral particle where two electrons are shifted from the neutral particle to the positive ion, i.e., charge transfer.
