| 摘要 |
<p>A cryostat includes a cryogen vessel 3, a thermal shield 6 and a bellows 20 filled with a gas. The bellows has a first end 22 in contact with a surface of the thermal shield and a second end 23 thermally coupled to the cryogen vessel. The gas may be nitrogen, argon, neon, helium or hydrogen, and the cryostat may house the windings of a superconducting magnet for an M.R.I imaging system. The thermal coupling may be via a high thermal conductivity section 25 which is pivotally mounted between the thermal shield and the cryogen vessel. The bellows may be of stainless steel, copper or aluminium material and it may be connected to the shield via a mount 34. The surface of the vessel may be provided with a high thermal conductivity layer, such as copper or aluminium, and the cryostat may also include a refrigerator (2 fig 1) to provide additional cooling to the thermal shield. The arrangement allows a reduction in the time taken to cool the thermal shield.</p> |
