The large influx of gas flow is required in an usual ion source for accelerating
3He ion in a cyclotron. For the RIKEN 160 cm variable energy cyclotron, a
3He circulation system has been devised so as to recover and purify the gas continuously. This is accomplished by a 50
l/min rotary pump which has vacuum-tight intake and exhaust. This pump, which is used as a fore pump of cyclotron evacuating system instead of proper one during
3He operation, recovers the gas and forces it to the ion source through a charcoal trap cooled by liquid nitrogen (Fig. 2). The volume of the system between the exhaust of the rotary pump and the ion source is designed as small as possible. The block diagram of the system is shown in Figs. 1 and 10.
4He (300cc. S. T. P.) is used instead of
3He to examine the performance of the system.
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