A He3circulation system for a cyclotron has been built which will recover the gas and purify it continuously. This is accomplished by modifying a mechanical vacuum pump to meet the following special requirements: intake and exhaust sealed for both pressure and vacuum; small volume on the exhaust side; minimum oil volume. This pump, which is used instead of the cyclotron forevac pump during He3operation, recovers the gas and forces it through a liquid nitrogen‐cooled charcoal trap and on to the ion source. The system is completely interlocked to ensure He3safety in the event of operator or electrical failure. With a flow rate of 6 cc per minute, the normal He3loss over a period of 200 hours operation was less than 3 cc per hour after an initial charge of 1000 cc NTP. With trap reactivation periods of 50 hours, no change in ion yield was observed. External beams of approximately 100 &mgr;a of doubly charged particles were obtained.