| 摘要 |
PURPOSE:To protect an intermediate-position cooling system by installing a thermal switch as follows: its lower-end side is connected thermally to a halfway position of a power lead; its upper-end side is connected thermally to a passage of a coolant liquid; it seals a working fluid inside, which is solidified when the lower-end side is at a definite temperature or lower and which thermally cuts off the lower-end side and the upper-end side. CONSTITUTION:When a valve 12 is opened in order to apply an electric current to a power lead 13, low-temperature helium gas flows inside a gas guide tube 10. Since a lower-part end plate 32 of a thermal switch 22 becomes a low temperature in this case, nitrogen which is sealed inside the thermal switch 22 is set to a solidified state; as a result, the inside of the thermal switch 22 is set to a vacuum state; the lower-part end plate 32 and an upper-part end plate 33 are set to a heat-insulating state. Accordingly, even when the low-temperature helium gas flows inside the gas guide tube 10, a cooling tube 23 of an intermediate-position cooling system 21 does not become a prescribed temperature or lower. Accordingly, liquid nitrogen flowing inside the cooling tube 23 is not frozen; the cooling tube 23 is not damaged. Thereby, it is possible to surely protect the intermediate-position cooling system 21. |
