Development of a New Compact ECR Ion Source with All Permanent Magnets for Carbon 5+Production

A compact accelerator for high energy carbon-ion radiotherapy (C-ion RT) has been studied at Heavy Ion Medical Accelerator in Chiba (IllMAC) of National institute of Radiological Sciences (MRS) since 2004. Compact accelerators have already been used for treatments at several C-ion RT facilities. The Electron Cyclotron Resonance Ion Source (ECRIS) with all permanent magnets (Kei series) [I] is used at these facilities. The Kei series has a magnetic field structure optimized for the production of C4+ ions. The operating cost can be further reduced by using an ion source optimized for C5+ production. Therefore, we have designed a new compact ECRIS with all permanent magnets to produce C5+ ions. At first, we aimed to determine the optimum mirror magnetic field for the production of a sufficient number of C5+ ions by using the-MRS-HEC [2] ion source. Experiments were performed to measure the beam currents of C5+ ions with various mirror magnetic fields, microwave power and frequency. As a result, we confirmed that the beam currents of C5+ ions could be achieved to more than 0.3mA with the coil currents of the electromagnets being optimized. Based on the parameters obtained from the test results this time, we will design a new ion source.