Development of the compact electron cyclotron resonance ion source for heavy-ion therapy

Carbon-ion cancer treatment is successfully being made at the Heavy Ion Med ical Accelerator in Chiba (HIMAC). Design philosophy for the ion sources fo r medical facilities are as follows: (1) sufficient beam intensity, a few h undred e mu A; (2) long lifetime with good stability; (3) easy operation an d easy maintenance; and (4) compactness. In order to develop such source fo r future heavy-ion facilities, we have tested compact electron cyclotron re sonance (ECR) ion sources using permanent magnets both for axial and radial confinement of hot electrons. Since the yield of C2+ ion in the first deve loped source (2.45 GHz ECR) was 15 e mu A and far below the medical require ment (similar to 150 e mu A for the HIMAC), a new source has been proposed, having a frequency of 10 GHz. The extracted intensity of C4+ (and C2+) ion s is expected to be higher than 200 e mu A. (C) 2000 American Institute of Physics. [S0034-6748(00)64302-2].