Patent ID: 7436179

Claim:
A magnet device comprising: a first magnetic field generation apparatus having a first annular coil case in which a cooling medium is filled; a second magnetic field generation apparatus arranged facing apart from the first magnetic field generation apparatus having a second annular coil case in which the cooling medium is filled; and a connecting member connecting the first magnetic field generation apparatus and the second magnetic field generation apparatus to each other, wherein each of said first and second magnetic field generation apparatuses includes a main coil, wherein said main coils of said first and second magnetic field generation apparatuses are positioned facing each other to form a static magnetic field space in between; wherein each of said first and second magnetic field generation apparatuses further includes external magnetic flux shielding coils placed between said main coil and the annular coil case, wherein said main coil and the external magnetic flux shielding coils of each of said first and second magnetic field generation apparatuses are arranged in the annular coil case, wherein the external magnetic flux shielding coils of each of said first and second magnetic field generation apparatuses have a first coil group and a second coil group having a coefficient of coil coupling greater than that of the first coil group, and said first coil group is connected in series to said second coil group.