IMPROVED THERMAL CONTACT BETWEEN CRYOGENIC REFRIGERATORS AND COOLED COMPONENTS

• US 20160061382A1
• Filed: 04/16/2014
• Published: 03/03/2016
• Est. Priority Date: 04/17/2013
• Status: Active Application

• Current Assignee: Siemens Healthcare Limited. (Siemens AG)
• Original Assignee: Siemens AG
• Inventors: SIMPKINS, Michael
• Granted Patent: US 10,253,928 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F17C 2227/0353 using cryocooler
• CPC Class Codes: F17C 3/085 Cryostats
• CPC Class Codes: F25B 9/14 characterised by the cycle used, e.g. Stirling cycle
• CPC Class Codes: F25D 19/006 Thermal coupling structure or interface
• CPC Class Codes: F28F 13/18 by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
• CPC Class Codes: G01R 33/3804 Additional hardware for cooling or heating of the magnet assembly, for housing a cooled or heated part of the magnet assembly or for temperature control of the magnet assembly
• CPC Class Codes: G01R 33/3815 with superconducting coils, e.g. power supply therefor
• CPC Class Codes: H01F 6/04 Cooling

Abstract

An arrangement for mounting a two stage cryogenic refrigerator (17) into a cryostat, the arrangement comprising a vacuum sock (15) for accommodating at least a part of the refrigerator, attachment means (32, 34) for attaching an upper part of the refrigerator to a surface (14) of the cryostat around an opening of the vacuum sock, a thermally conductive portion (26) of a wall of the vacuum sock which, in use, is thermally and mechanically in contact with a second cooling stage (24) of the refrigerator, and arrangements (40, 42) are provided for thermally connecting a first stage (22) of the refrigerator to a thermal radiation shield (16) of the cryostat.

Claims

1. An arrangement for mounting a two stage cryogenic refrigerator, having first and second cooling stages in succession, into a cryostat, the arrangement comprising:

a vacuum sock at least a part of the refrigerator;

an upper part of the refrigerator to a surface of the cryostat around an opening of the vacuum sock;

said vacuum sock having a wall with a thermally conductive wall portion that in use, is thermally and mechanically in contact with the second cooling stage of the refrigerator;

thermal connectors that thermally connect the first cooling stage of the refrigerator to a thermal radiation shield of the cryostat, said thermal connectors comprising a bellows structure that is in a retracted position when the vacuum sock is at atmospheric pressure, and that is in an extended position when the vacuum sock is under vacuum so the bellows presses a thermally conductive contact piece into thermal and mechanical contact with the first cooling stage of the refrigerator;

and the refrigerator being elongate in an axial direction, and the bellows structure retracting and extending in a radial direction, perpendicular to the axial direction; and

said second cooling stage is pressed in the axial direction in contact with the thermally conductive portion of the wall of the vacuum sock, by atmospheric pressure acting on the upper part of the refrigerator, when the vacuum sock is under vacuum.

2. An arrangement according to claim 1 comprising a thermally conductive grease on mating surfaces of the contact piece and the first cooling stage.

3. An arrangement according to claim 1 comprising indium on one or both of the mating surfaces of contact piece and the first cooling stage.

6. An arrangement according to claim 1, wherein the bellows structure comprises an interface piece that is thermally linked to the thermal radiation shield by a thermal path which that includes a flexible thermal conductor

7. An arrangement according to claim 6 wherein the flexible thermal conductor passes through the bellows structure.

8. An arrangement according to claim 1 wherein the bellows structure is open at a radially outer end thereof, and a flexible thermal conductor passes from conductive contact piece, through the bellows structure and out of the bellows structure through the open radially outer end.

14. An arrangement as claimed in claim 7, comprising a bearing surface, mechanically retained in position with respect to said sock, and wherein said bellows structure is situated to bear on the contact piece and the bearing surface.

4-5. -5. (canceled)

9-12. -12. (canceled)

13. An arrangement for mounting a two stage cryogenic refrigerator into a cryostat, the arrangement comprising:

a vacuum sock for accommodating at least a part of the refrigerator;

attachment means for attaching an upper part of the refrigerator to a surface of the cryostat around an opening of the vacuum sock;

a thermally conductive portion of a wall of the vacuum sock which, in use, is thermally and mechanically in contact with a second cooling stage of the refrigerator;

arrangements are provided for thermally connecting a first stage of the refrigerator to a thermal radiation shield of the cryostat;

the said arrangements comprising a bellows structure within the vacuum sock, the bellows structure containing a sealed mass of cryogen gas, whereby said bellows structure is in a retracted position when the vacuum sock is at atmospheric pressure, and which is in an extended position when the vacuum sock is under vacuum, wherein, in its extended position, the bellows presses a thermally conductive contact piece into thermal and mechanical contact with a first cooling stage of the refrigerator; and

wherein the thermally conductive contact piece is arranged to rotate about an axle in response to the bellows structure being in a retracted position when the vacuum sock is at atmospheric pressure, and being in an extended position when the vacuum sock is under vacuum.