TSVDシミング計算とMRI磁石を用いた超良好一様（±0.1 ppm）磁場実現のシミング試験

Two muon experiments, which require extremely homogeneous magnetic fields, are under preparations in J-PARC. One of the experiments is the MuSEUM（Muonium Spectroscopy Experiment Using Microwave）experiment that requires＋/-0.1 ppm homogeneity in a spheroidal volume of 20 cm in diameter and 30 cm in length. To confirm that such an extremely homogeneous magnetic field can be obtained in a whole-body MRI magnet, intensive shimming tests were conducted using a shimming calculation based on TSVD of linear algebra with a passive shimming structure. In the first shimming test, we found that small shim-piece unit is necessary, and in the second test an extremely homogeneous magnetic field was realized with Ni shim plates, the magnetic moment of which is 1/6 of the ordinal Fe shim plates of MRI magnetic field. This result confirms that an extremely homogeneous magnetic field can be realized for the experiment.