Superconducting magnet with magnetic shielding

An open superconductive magnet comprising:

• a) a generally longitudinally extending axis;
• b) a plurality of spaced-apart, generally parallel, and generally longitudinally extending structural posts;
• and
• c) two generally identical magnet assemblies disposed in mirror image relationship about a plane oriented generally perpendicular to said structural posts and positioned generally equidistant from said magnet assemblies, wherein said magnet assemblies are longitudinally spaced-apart by said structural posts to create an intervening open space, and wherein each said magnet assembly includes:
• (1) a generally annularly-cylindrical-shaped housing generally coaxially aligned with said axis, having annular, longitudinally-spaced-apart first and second end walls with said second end wall facing outwardly generally toward said open space, and having radially-spaced-apart outer and inner cylindrical walls, wherein said first end wall and said outer cylindrical wall are generally magnetizable walls, and wherein said second end wall and said inner cylindrical wall are generally non-magnetizable walls;
• (2) a superconductive coil assembly having at least one generally solenoidal-shaped main superconductive coil which is generally coaxially aligned with said axis, which is disposed within and generally spaced apart from said housing, and which has a number of ampere turns;
• and
• (3) a generally annular first permanent magnet generally coaxially aligned with said axis, disposed outside said housing longitudinally proximate said first end wall, having a number of equivalent ampere turns, and having a magnetic field direction oriented generally parallel to said axis pointing towards said second end wall.

An open superconductive magnet comprising:

• a) a generally longitudinally extending axis;
• b) a plurality of spaced-apart, generally parallel, and generally longitudinally extending structural posts;
• and
• c) two generally identical magnet assemblies disposed in mirror image relationship about a plane oriented generally perpendicular to said structural posts and positioned generally equidistant from said magnet assemblies, wherein said magnet assemblies are longitudinally spaced-apart by said structural posts to create an intervening open space, and wherein each said magnet assembly includes:
• (1) a generally annularly-cylindrical-shaped housing generally coaxially aligned with said axis, having annular, longitudinally-spaced-apart first and second end walls with said second end wall facing outwardly generally toward said open space, and having radially-spaced-apart outer and inner cylindrical walls, wherein said first end wall and said outer cylindrical wall are generally magnetizable walls, and wherein said second end wall and said inner cylindrical wall are generally non-magnetizable walls;
• (2) a superconductive coil assembly having at least one generally solenoidal-shaped main superconductive coil which is generally coaxially aligned with said axis, which is disposed within and generally spaced apart from said housing, and which has a number of ampere turns;
• and
• (3) a generally annular permanent magnet generally coaxially aligned with said axis, disposed outside said housing radially proximate said outer cylindrical wall and longitudinally proximate said second end wall, having a number of equivalent ampere turns, and having a magnetic field direction oriented generally perpendicular to said axis pointing towards said axis.