| 摘要 |
PURPOSE:To carry out heat exchange with a superconducting coil effectively, to reduce use of freezing mixture during pre-cooling and to prevent quenching caused by temperature difference inside a helium bath by forming a cooling path inside a magnetic shield core. CONSTITUTION:During pre-cooling, liquid nitrogen injected form an injection tube 19 of freezing mixture reaches lower space 17 of a helium bath 11 through lower paths 20b, 21b from upper paths 20a, 21a of a magnetic shield core 16 via a hollow section 16c wherein a superconducting coil 15 is contained. Liquid nitrogen stored in the space 17 evaporates upward moving backward in the flow path. Thermal conversion is carried out effectively to the freezing mixture through cooling paths 20, 21 which come into direct contact with the coil 5 or pass through thereabouts. In main cooling, the coil 15 and the core 16 are immersed in liquid helium 12. A temperature difference generates in upper part and lower part of the bath 11 in this state; however, convection generates through the paths 20, 21, thereby cooling the coil 15 well and preventing development of quenching inside the coil 15. |
