PROBLEM TO BE SOLVED: To provide an electromagnet unit comprising a shim coil which is capable of generating such a correction magnetic field as canceling a disturbance magnetic field.SOLUTION: An electromagnet unit comprises a plurality of magnetostatic coils of which the center axes are matched to each other, and generates magnetostatic fields in parallel with the center axes in a uniform magnetic field region. The electromagnet unit further comprises a plurality of shim coils (No.1 to No.6) for improving uniformity of magnetic fields in the uniform magnetic field region by generating a magnetic field which is capable of canceling magnetic fields in an arbitrary radial direction of the magnetostatic coils approximately vertical to the center axes generated in the uniform magnetic field region. The magnetostatic coil is a superconducting coil and the shim coil 1 includes the superconducting coil. Magnetic flux storage in a superconducting state of the superconducting coils is utilized to passively cancel an error magnetic field caused by the outside. The superconducting coils of the magnetostatic coils and the shim coils 1 are operated under a permanent current mode.COPYRIGHT: (C)2013,JPO&INPIT【課題】外乱磁場を打ち消すような補正磁場を発生できるシムコイルを備えた電磁石装置を提供する。【解決手段】互いに中心軸が一致する複数の静磁場コイルを有し、中心軸に平行な方向の静磁場を均一磁場領域に発生させる電磁石装置において、均一磁場領域に生じる中心軸に略垂直な方向の内の静磁場コイルの任意の半径方向の磁場を、打ち消せる磁場を発生させ、均一磁場領域における磁場の均一性を向上させる複数(No.1~6)のシムコイル1を有する。静磁場コイルは超伝導コイルであり、シムコイル1は超伝導コイルを有し、これらの超伝導コイルの超伝導状態における磁束保存を利用して受動的に外部由来の誤差磁場を打ち消す。静磁場コイルとシムコイル1の超伝導コイルは、永久電流モードで運転する。【選択図】図1
