Commissioning and performance of the HIMAC medical accelerator

Heavy ions show the excellent dose concentration especially at a position located deep in a human body. This character of heavy ions are well suited for the medical treatment of the cancer. A heavy ion synchrotron complex, HIMAC, has been constructed at NIRS for this purpose. The HIMAC accelerator consists of an injector linac, a couple of synchrotron rings, long and complicated beam transport lines, three treatment rooms and four experimental rooms. The maximum energy of the synchrotron is determined so that the residual range of silicon ions exceeds 30 cm in water. The clinical trials of the cancer treatment started on June 21 using a 290 MeV/u carbon beam, and 21 patients were treated by the end of February 1995.