| 摘要 |
PURPOSE:To obtain an economical cryostat which can reduce the quantity of evaporation and loss, by providing a refrigerator which recondenses the helium gas evaporated in a liquid helium tank, and by placing the cold head of the refrigerator in the liquid helium tank. CONSTITUTION:The pressure in a liquid helium tank 4 is kept at a specified pressure P with a pressure-controlling means 45. If an extraordinally high- pressure is generated, increased evaporated gas GHe is released outside safely by the pressure-controlling means 45, and the pressure in the liquid helium tank 4 is prevented from rising extraordinally high. This enables reducing the cost, as a well-known 4.3K helium refrigerator becomes usable as a refrigerator 7 for the recondensation. Besides, the cold head 71 of this refrigerator 7 recondenses the helium gas GHe immediately, evaporated in the liquid helium tank 4. Accordingly, the quantity of the evaporation is greatly reduced. In addition to this, the loss of the liquid helium LHe is decreased, and a superconducting coil 6 is held in a state of very low temperature and functions properly for a long time as a superconducting magnet. |
