| 摘要 |
<p>PURPOSE:To substantially decrease the consumption of liquid He due to evaporation, by adding a miniature He cooling apparatus and providing a power lead with a second thermal anchor having a predetermined temperature characteristics. CONSTITUTION:A miniature He cooling apparatus 8 is fixed to an external tank container 5, and a second thermal anchor 17 is provided from the low-temperature end 8a to a power lead 6. The thermal anchor 17 is made of such a material that has its maximum heat conductivity at a temperature (20-30 deg. K) lower than the corresponding temperature (77 deg. K) of a first thermal anchor from a heat shield plate 4, and preferably made of oxygen-free copper or electrolytic copper. According to this construction, any heat penerating through the lead 6 when no electricity is supplied is absorbed by the first anchor 7, and the heat penerating from the first anchor 7 is absorbed by the anchor 17. Thus, an internal tank 1 is penetrated only by the heat from the anchor 17, and therefore the evaporation of liquid He within the tank 1 is reduced. When electricity is supplied, the temperature of the anchor 17 is also increased as the temperature of the lead 6 is increased. However, since the heat conductivity of the anchor 17 is decreased, the lead 6 applies no excessive heat load abruptly to the low-pressure end 8a. The operation of the cooling apparatus 8 can thus be kept properly balanced.</p> |
