ION SOURCES FOR INDUCTION LINAC DRIVEN HEAVY-ION FUSION

The use of ion sources in induction linacs for heavy ion fusion is fun damentally different from their use in the rf linac-storage rings appr oach. Induction linacs require very high current, short pulse extracti on usually with large apertures which are dictated by the injector des ign. One is faced with the problem of extracting beams in a pulsed fas hion while maintaining high beam quality during the pulse (low emittan ce). Four types of sources have been studied for this application. The vacuum arc and the rf cusp field source are the plasma-types and the porous plug and hot alumino-silicate surface source are the thermal ty pes. The hot alumino-silicate potassium source has proved to be the be st candidate for the next generation of scaled experiments. The porous plug for potassium is somewhat more difficult to use. The vacuum arc suffers from noise and lifetime problems and the rf cusp field source is difficult to use with very short pulses. Operational experience wit h all of these types of sources is presented.