PROBLEM TO BE SOLVED: To provide an operator with similar operability to that of the conventional machine by an electromagnetic device highly precisely retaining magnetic field distribution by adjusting the magnetic field for each intrinsic mode acquired by a singular value decomposition.SOLUTION: The magnetic field adjustment apparatus acquires intensity of an intrinsic mode from a measurement magnetic field, calculates a current for each intrinsic mode of negative feedback control according to the magnetic field, obtains a current for each shim coil by adding the current for each mode, and controls a coil current so as to become the current value. An interface for operators represents a target of a correction magnetic field and a magnetic field of a shim coil by a spherical harmonics method. Consequently, this configuration can provide the apparatus capable of highly accurately adjusting the magnetic field, regardless of operability similar to that of the conventional one.SELECTED DRAWING: Figure 1【課題】特異値分解により得た固有モード毎に磁場調整することで精度良く磁場分布を保つ電磁石装置で、操作者には従来機と同様な操作性を提供する。【解決手段】計測磁場から固有モードの強度を求め、その磁場に応じた負帰還制御の固有モード毎の電流を算出し、その電流をモード毎に加算して各シムコイルの電流を求め、その電流値になるようにコイル電流を制御する。操作者向けインターフェースでは、球面調和関数強度で補正磁場の目標やシムコイルによる磁場を表示する。そのため、従来同様の操作性でありながら精度良い磁場調整が可能となる装置を提供できる。【選択図】図１
