A hexapole magnet for a 14.5 GHz electron cyclotron resonance (ECR) ion source, where the maximum radial field on the wall of the plasma chamber is higher than 1.1 T, has been designed and fabricated. The size of the outer diameter and the number of the sector of the hexapole are optimized for a 14.5 GHz ECR ion source with the help of a three-dimensional field calculation code. Moreover, to make a strong and long-life magnet against the demagnetic field on the hexapole multilayered structure in radial and axial directions is considered in the design. The distributions of the demagnetic fields are estimated by the calculation of the radial field in a hexapole magnet and the axial field from the solenoid coils. Proper grades of magnetic materials depending on the strength of the demagnetic field are applied for the different layers. The magnetic fields of the measured and calculated ones have been compared.
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