| 摘要 |
PURPOSE:To unnecessitate a magnetic shield surrounding a cryostat entirely, by a method wherein a part of the wall constituting the vacuum vessel of the cryostat in which a superconductive magnet will be housed is formed with a magnetic material, other part is formed into non-magnetic material, and the cryostat is surrounded by a magnetic shield. CONSTITUTION:The wall 18 and the upper and the lower walls on the outer circumference of a vacuum case are formed using the magnetic material of the thickness required for magnetic shielding, the wall 21 of the inner circumference is made of a non-magnetic material, and the space 17 of magnetic field of normal temperature is provided at the center part of the cryostat. Then, supporting members 22 and 23 are interposed between the walls 18-20 and a magnet 12. Said supporting materials 22 and 23 have the strength withstanding sucking force, and the material having low thermal conductivity is used for them in order to prevent the penetration of heat into a liquid helium vessel 11 from a normal temperature part. As the wall, excluding the surface where magnetic field is applied, is constituted by a magnetic material, a large magnetic shield surrounding the entire cryostat can be unnecessitated. |
