DEVELOPMENT OF THE NATIONAL INSTITUTE OF RADIOLOGICAL SCIENCES ELECTRON-CYCLOTRON-RESONANCE ION-SOURCE FOR THE HEAVY-ION MEDICAL ACCELERATOR IN CHIBA

The development of an electron cyclotron resonance ion source for the heavy ion medical accelerator in Chiba (HIMAC) injector is reported. T he HIMAC is a heavy ion medical accelerator for cancer therapy. The el ectron cyclotron resonance (ECR) ion source is expected to provide a l ong lifetime, easy operation, and easy maintenance for medical use. Th e NIRS-ECR ion source has a single closed ECR stage, and a microwave f requency of 10 GHz is applied. Under the present performance, the outp ut electrical currents of the ions are 2500 emuA for He-1+, 300 emuA f or C2+, 480 emuA for Ne3+, and 110 emuA for Ar6+. Stability of the int ensity is better than 2%. The transmission efficiency through a low-en ergy beam-transport line with an acceptance of 200 pimm mrad is more t han 70%; the typical 50% and 90% emittances of the injection beam with 8 keV/u are 20 and 80 pimm mrad, respectively. These performances sat isfy the requirements for radiotherapy.