| 摘要 |
<p>A cryogenic cooling apparatus 100 has a supply gas line 3A and a return gas line 3B coupled to a compressor 1 driven by a motor 8. A coupling element 4, such as a rotary valve, is able to provide gas flow between the compressor and a two-stage mechanical refrigerator 2 via the supply and return gas lines, and the pressure of the supplied gas is modulated by the coupling element in a cyclical manner. A sensing system 6 is used to monitor the operational state of the refrigerator and a control system 5 modulates the frequency of the cyclical gas pressure supplied by the coupling element in accordance with the monitored operational state. The refrigerator second cooled stage can be thermally coupled with an object to be cooled (103 Fig 2), and a selectively coupleable thermal link (110 Fig 2), for example a heat pipe, allows thermal coupling of the refrigerator first and second cooled stages (101, 102 Fig 2) depending upon the operational state of the refrigerator. A method of use of the apparatus is also disclosed, and the apparatus and method have particular application in a Magnetic Resonance Imaging system.</p> |
