Vacuum System of the Ion Source and Injection Line of a High Current Compact Cyclotron

A 2.45 GHz microwave ion source and the transport system of high current proton beam for injection study in a compact cyclotron have been designed, fabricated indigenously, installed and commissioned. Presently it is under testing for beam characterization and inflection study. The vacuum system consists of a plasma chamber with 8mm slit in the plasma electrode, two-segment ceramic insulators (Al2O3) column, which supports the beam extraction electrodes and isolates the high voltage deck from the beam line and a 3m long low energy beam transport line (LEBT) equipped with several diagnostic elements such as faraday cup, slits, beam viewer etc. There is a provision to connect a needle valve to feed gas into the chamber for beam space charge neutralization studies. An online vacuum data logging software has been developed for continuous monitoring of the vacuum near the extraction zone. Monitoring system being very sensitive to the high voltage breakdown, is designed with a spark protection circuit which provides an isolation of 10kV using an optical isolation technique. In this paper we present design philosophy, operating experience and some experimental results. We have studied the behaviour of vacuum system near the extraction zone under various operating conditions of the high current ion source.