| 摘要 |
PURPOSE:To prevent a cryostat having power leads to introduce a high-voltage current from becoming larger by raising the level of the liquid helium only by a needed insulating distance to provide an insulation capable of withstanding a high voltage. CONSTITUTION:The power lead has a double cylinder structure: arranged outside a hollow, hermetic conducting portion 31 made of electrically good conductor is a hermetic pressure-reducing pipe 32 of bad conductor. Allowing the gas in the pipe 32 to escape to a helium recovery system causes the gas pressure in a helium liquid- level suction pipe 34 to lower and the internal pressure to raise the liquid helium into the pipe 34. In order to allow the height raised to maintain a needed insulation distance as well as to prevent the liquid helium from directly flowing into a communication pipe 36, an arithmetical pressure-reducing valve 40 is provided to keep the difference between the gas pressures in the helium container and the pressure- reducing pipe 32. Thus, the insulation against a high voltage is provided by raising the level of the liquid helium only by a needed insulation distance. This prevents the cryostat from becoming larger. |
