Design of compact ECR ion source for the multi ion dadiotherapy

The multi-ion radiotherapy with dose distribution and Liner Energy Transfer optimization is being studied at QST-NIRS. Helium, carbon, oxygen and neon ions are considered as ion species for multi-ion radiotherapy. A basic experiment using these ion beams has being carried out at the HIMAC. We have developing the new ECR ion source with all permanent magnets for multi-ion radiotherapy. Ionization gases were helium, methane, oxygen, and neon to produce He²⁺, C⁴⁺, O⁶⁺ and Ne⁷⁺ ions. Requirement values of beam current were 940 μA correspond to He²⁺, 290 μA to C⁴⁺, 330 μA to O⁶⁺, and 245 μA to Ne⁷⁺. We did some beam tests for design of compact ECR ion source at existing the 18 GHz NIRS-HEC ion source. In order to reproduce the magnetic field during experiments of NIRS-HEC, the structure of the permanent magnet was examined using the POISSON/SUPERFISH code. As a result of the calculation, it was found that a sufficient magnetic field could be obtained. Therefore, the structure of the ion source such as plasma chamber, extraction electrode, introduction of microwave and gas was injection examined according to the structure of the permanent magnet. (author)