Reliable Beam Supply for Cancer Radiotherapy with Carbon Beam
-Status Report of the HIMAC Control System-

E. Takada, N. Araki, T. Kohno, M. Torikoshi,
S. Yamada, and Accelerator Group
Division of Accelerator Physics & Engineering,
National Institute of Radiological Sciences, JAPAN

Heavy Ion Medical Accelerator in Chiba, HIMAC, was commissioned November '93 and commenced clinical trial of cancer treatment in June '94 after several physics and radiobiological experiments. Since then, a total of 55 patients have been treated with carbon beam of 290 MeV/u, 350 MeV/u, and 400 MeV/u. HIMAC, made of ion sources (ECR & PIG), injector linacs (RFQ & DTL), two synchrotron rings, and transport systems to clinical and experimental ports was operated stably with a distributed control system. Operational performance of the system during this period is reported with its problems and improvements. An important point is that daily operation and routine maintenance work is carried out by AEC, a company recently established for accelerator operation, under the contract with NIRS. Therefore, the control system must provide man-machine interface to operators whose background is not an accelerator-oriented one. The system was designed to meet this requirement, and the experiences of the first two years show that it basically satisfies the design goal, while revision and enhancement of few functions are under way.