| 摘要 |
A short-term thermally stable cryostat (40). The cryostat (40) pre-cools an incoming high-pressure gas, converts the gas to a cold liquid, and cools an item by allowing the liquid to acquire heat from the item and boil into an exhaust gas, while maintaining a constant flow rate of the exhaust gas to reduce thermal noise due to flow rate modulation. The cryostat (40) includes an evacuated space (58) therein containing the item to be cooled and an inner cooling volume (64). Pre-cooling fins (44) spiral around a hollow mandrel (52) within the cooling volume (64) and circulate an incoming high-pressure gas around the mandrel (52). A flow restrictor (60) receives the incoming gas from the pre-cooling fins (44) and releases it into the cooling volume (64), thereby convening the incoming gas into a cold liquid which can acquire heat from the item and boil into an exhaust gas. A pressure back plate (46) having a channel therein confines a first volume of the exhaust gas flowing past the pre-cooling fins (44) to pre-cool the incoming gas. A first flow valve (68) in communication with the pressure back plate (46) controls the flow rate of the first volume of the exhaust gas as the first volume of the exhaust gas is vented to the local atmospheric pressure air, and a second flow valve (70) in communication with an end of the mandrel (52) controls the flow rate of a second volume of exhaust gas flowing through the mandrel (52).
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