Abstract: A pulse tube refrigerator comprising a cold head, wherein the cold head comprises at least one pulse tube (6) and at least one regenerator (7); the cold head having a cold end (8) and a warm end (5), each end being provided with respective heat exchangers (12, 13); wherein refrigerant is supplied (3) to the cold head; and wherein the warm end heat exchanger (13) is provided with a secondary cooling mechanism (16, 17) to improve the efficiency of the PTR.

Abstract: A cryogenic chamber comprising an outer vacuum vessel (9), an inner cryogen vessel (11), a turret (40) housing a neck tube (8) itself providing external access to the inner cryogen vessel (11), and a pulse tube refrigerator (20) itself comprising at least one pulse tube and at least one regenerator tube. The pulse tube refrigerator is located within a vacuum contained between the outer vacuum vessel (9) and the inner cryogen vessel (11) and the pulse tube refrigerator (20) and the neck tube (8) share a single turret (40). The cooling stage(s) (6, 7) of the pulse tube refrigerator (20) is/are rigidly mechanically connected to the neck tube (8) by highly conductive thermal links. The pulse tube(s) and regenerator tube(s) are displaced away from the neck tube and from each other.

Abstract: A pulse tube refrigerator comprising a cold head, wherein the cold head comprises at least one pulse tube (6) and at least one regenerator (7); the cold head having a cold end (8) and a warm end (5), each end being provided with respective heat exchangers (12, 13); wherein refrigerant is supplied (3) to the cold head; and wherein the warm end heat exchanger (13) is provided with a secondary cooling mechanism (16, 17) to improve the efficiency of the PTR.

Abstract: A pulse tube refrigerator comprises a fixed pressure casing (3) containing cold parts and a removable pressure casing (2) containing serviceable parts. The fixed pressure casing (3) and the removable pressure casing (2) are coupled together via a joining member (1). During cooling operation the joining member (1) is arranged such that refrigerant fluid flows between the fixed and the removable casings. During servicing the joining member is arranged to cut off flow of refrigerant fluid between the fixed and removable casings, such that refrigerant in the fixed casing is trapped and parts in the removable casing are accessible for servicing. After servicing, substantially pure refrigerant fluid is pumped into the removable casing (2), the fixed and removable casings are re-joined and the joining member (1) is arranged such that refrigerant fluid flows between the casings again.

Abstract: A cryogenic chamber comprising an outer vacuum vessel (9), an inner cryogen vessel (11), a turret (40) housing a neck tube (8) itself providing external access to the inner cryogen vessel (11), and a pulse tube refrigerator (20) itself comprising at least one pulse tube and at least one regenerator tube. The pulse tube refrigerator is located within a vacuum contained between the outer vacuum vessel (9) and the inner cryogen vessel (11) and the pulse tube refrigerator (20) and the neck tube (8) share a single turret (40). The cooling stage(s) (6, 7) of the pulse tube refrigerator (20) is/are rigidly mechanically connected to the neck tube (8) by highly conductive thermal links. The pulse tube(s) and regenerator tube(s) are displaced away from the neck tube and from each other.

Abstract: A pulse tube refrigerator comprises a fixed pressure casing (3) containing cold parts and a removable pressure casing (2) containing serviceable parts. The fixed pressure casing (3) and the removable pressure casing (2) are coupled together via a joining member (1). During cooling operation the joining member (1) is arranged such that refrigerant fluid flows between the fixed and the removable casings. During servicing the joining member is arranged to cut off flow of refrigerant fluid between the fixed and removable casings, such that refrigerant in the fixed casing is trapped and parts in the removable casing are accessible for servicing. After servicing, substantially pure refrigerant fluid is pumped into the removable casing (2), the fixed and removable casings are re-joined and the joining member (1) is arranged such that refrigerant fluid flows between the casings again.

Abstract: A refrigerator for cooling a sample (16,17) comprising a reservoir (1) for storing gaseous .sup.4 He when in use; a cooler (13) for cooling gaseous .sup.4 He from the reservoir; and a helium vessel (18,19) for containing .sup.4 He, the .sup.4 He in the helium vessel being in fluid communication with the reservoir (1) via the cooler (13). The sample (16,17) is mounted, in use, in thermal contact with the .sup.4 He in the helium vessel whereby the .sup.4 He in the helium vessel provides a path for heat to transfer from the sample to the cooler.