Patent ID: 7000408

Claim:
A superconducting magnet apparatus comprising: a vacuum vessel; a superconducting coil accommodated in the vacuum vessel; and one or more refrigerators attached to the vacuum vessel to cool the superconducting coil, wherein the refrigerator comprises: a motor drive; a displacer attached to the motor drive and driven by the motor drive; and a cooling cylinder accommodating the displacer so as to allow the displacer to reciprocate, the vacuum vessel being formed of a double-cylindrical structure having a hollow space in its center, a sleeve being provided in the vacuum vessel to accommodate the cooling cylinder by isolating it from a vacuum area in the vacuum vessel, and the sleeve having an opening near the wall of the vacuum vessel, the cooling cylinder being partly in surface contact with the sleeve, an opening portion of the cooling cylinder through which the displacer is inserted having a first flange to which the motor drive is installed with the displacer inserted therein and also having a cylindrical portion inserted into the sleeve to seal the space in the sleeve, and a sealing ring being provided between the cylindrical portion and an inner wall of the sleeve that opposes the cylindrical portion, the motor drive and the displacer being capable of removing from the vacuum vessel, leaving the first flange and the cooling cylinder.