| 摘要 |
PURPOSE:To improve the detection accuracy of the leak test by reducing the adsorbing capability of the adsorbing agent by heating at the leak test of a liquid helium gas, thereby preventing the adsorbing agent from adsorbing the leakage gas. CONSTITUTION:In conducting a leak test at the initial cooling time, when a gas supply valve 10 is first closed, an evacuation valve 11 is opened, and thermal switch 6 is evacuated by a vacuum pump, then a bellows 25 contracts and plate bodies 23 and 26 depart, whereby the plate bodies 23, 26 have only very small heat transfer due to radiation and the thermal switch 6 is turned off. If a heater 7 is heated in this condition, an adsorbing agent 8 is deprived of the adsorbing capability, and the same condition is provided as that there is no adsorbing agent 8 in a vacuum container 3. Therefore, since the leakage gas is not adsorbed by the adsorbing agent 8 if a liquid helium gas is leaking out from a very low temperature cell, the leakage gas can positively detected, thereby improving the detection accuracy of the leak test. |
