Optimization of hexapole magnet for ECR ion source

Abstract

The magnet field strengths with respect to the size of permanent magnet and to the number of magnet pieces have been investigated in order to optimize the strength for ECR (Electron Cyclotron Resonance) ion source. The shape of hexapole magnet consisting of 24 permanent magnet pieces, and the diagram of dependence of the magnet field strength on the size of hexapole magnet were shown in figures. It was found from the above diagram that the magnetic field did not depend on the internal radius of hexapole magnet, when the magnetic field was made by magnets with different size. The magnetic field strength has been calculated as a function of the number of magnet pieces. The magnet field strength increased with the number of pieces, however, the saturation of the strength appeared from 24 or 30 pieces suggesting the number to be reasonable.

電子サイクロトロン共鳴(ECR)イオン源の強度を最適化するために、永久磁石のサイズおよび磁石の個数に関して磁場強度を検討した。24個の永久磁石から構成する6極磁石の形状、および6極磁石のサイズに対する磁場強度依存性のグラフを図示した。グラフから、磁場がサイズの異なる磁石で構成されると磁場は6極磁石の内径には依存しないことが分かった。磁石の個数の関数として磁場強度を計算した。個数の増加に伴い磁場強度は増加するが、24個あるいは30個で飽和し、それが妥当な個数であること示唆した。