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- A. Kitagawa, M. Muramatsu, Y. Sakamoto
NIRS, Chiba-shi, Japan
- S. Biri
ATOMKI, Debrecen, Hungary
- A.G. Drentje
KVI, Groningen, The Netherlands
- T.F. Fujita
National Institute of Radiological Sciences, Chiba, Japan
- T. Sakuma, N. Sasaki, T. Sasano, W. Takasugi
AEC, Chiba, Japan
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Since 1994, heavy-ion radiotherapy using carbon ions is successfully carried out with the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). Over 5000 cancer patients have already been treated with 140-400 MeV/u carbon beams. These clinical results have clearly verified the advantages of carbon ion. The ion source needs to realize a stable beam with the same conditions for daily operation. Maintenance is restricted to once per year. However, the deposition of carbon on the wall of the plasma chamber is normally unavoidable. This causes an ‘anti-wall-coating effect’, i.e. a decreasing of the beam (typically 50 % after a few months of operation), especially for the higher charge-state ions due to the surface material of the wall. The ion source has - even in this bad condition – still to produce a sufficiently intense and stable beam. We summarize our experience during 16 years of operation and show the scope for further developments. HIMAC is dedicated to radiotherapy, but it has as a second essential task to operate as a facility for physicist users. In that scope it accelerates many ion species for basic experiments. In order to serve all HIMAC users at best, the extension of the range of ion species is an important subject in ion source development. For example, in order to increase the ECRIS-beam intensity for heavier ions, microwave is applied at different frequencies by a traveling wave tube amplifier and….?
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