| 摘要 |
A service neck and refrigerator assembly for a cryostat comprises a service neck tube 22 which houses a tube 23 able to carry electrical power into the cryostat, eg for introducing current into a superconducting magnet coil through an electric cable 58. A refrigerator 30, preferably a two-stage refrigerator, is housed in a sock 31. A low-temperature cooling stage 54 of the refrigerator is connected directly via a heat pathway 24 to the service neck 22. The pathway 24, preferably formed by a continuous piece of copper, is exposed to the inside of the service neck to form a recondensing surface 44. Boiled-off cryogen vapour from the liquid cryogen vessel 10 recondenses on the surface 44 and thereafter flows back into the liquid cryogen vessel 10. In another embodiment (see Fig.2) the refrigerator sock 31 is filled with a cryogen, such as helium, which in operation recondenses on the cooling stage 54 before dripping onto the heat pathway 24. The surface of the pathway 24 which is exposed to the interior of the service neck is ribbed to increase the surface area available for recondensation. |
