In-terminal ECR Ion Source of the Tandem Accelerator at JAERI

Electron Cyclotron Resonance Ion Source(ECRIS)s are able to produce intense beams of highly charged positive ions and used injection system for cyclotron, linac as well as experiments of atomic physics. The tandem accelerator system has been benefiting from use of an electron stripper at the high voltage terminal. The most probable charged state after a foil stripper is, however, much lower than the highest charge state of ions with an intensity of more than several emA from a high performance ECRIS. With respect to beam current, the life time of stripper foils decrease with increasing beam current. Especially for very heavy ions, it is difficult to obtain a stable and intense beam for a long time without foil exchange. Use of an ECRIS in a tandem accelerator is expected to increase beam intensity, beam energy and beam species. A small permanent magnet ECRIS has been installed in the high voltage terminal of the vertical and folded type 20UR Pelletron tandem accelerator at Japan Atomic Energy Research Institute at Tokai. The ECRIS is placed in a severe environment; i.e. in the high pressure SF6 gas and under an attack of electric surges from occasional high voltage sparks in the accelerator. For this reason, the injection system initially need to be simple and to have minimum functions. The optimum condition and the simplification of the operation parameters were searched on the assumption of installing the ion source in the tandem accelerator. The result of this experiment enable us to reduce the five operational parameters to the three which were the gas flow, bias voltage and the RF power. Acceleration tests have been successfully carried out with beams of H+, N2+, O3+, 5+, Ar6+, 8+, 9+ and 132Xe12+, 13+ ions. The beam profiles were very sharp at the image point of the analyzing magnet.