| 摘要 |
A cryostat for transporting cooled equipment at an upper cryogenic temperature, where the cryostat is arranged to cool the cooled equipment by a working cryogen 2, such as liquid helium, which boils at a lower cryogenic temperature. The cryostat comprises a vacuum container 4 surrounding the cooled equipment defining an evacuated layer between the vacuum container and the cooled equipment. A getter material 20 is placed within the evacuated layer so as to absorb molecules of a vacuum contaminant, such as hydrogen, which is present in a gaseous form within the evacuated layer at the upper cryogenic temperature but which is retained in a liquid or solid form at the lower cryogenic temperature. The cooled equipment may be housed in a cryogen vessel 1 and cooled by a cooling loop arrangement. Preferably, the getter material is in the form of a flat foil composed of an adhesive backed aluminium carrier sheet coated with a titanium-vanadium alloy overlaid with a palladium layer. The getter material may be attached to an inner surface of the vacuum container, an outer surface of the cryogen vessel, or a thermal shield 5 located within the evacuated layer. Preferably, the getter material is selective to a contaminant gas having a boiling or sublimation point between the lower cryogenic temperature and the upper cryogenic temperature. |
