Cryogenic cooling system

Patent metadata

Field	Value
Publication number	US-11333404-B2
Application number	US-201916441560-A
Country	US
Kind code	B2
Filing date	Jun 14, 2019
Priority date	Jun 19, 2018
Publication date	May 17, 2022
Grant date	May 17, 2022

Abstract

A cryogenic cooling system is provided comprising: a mechanical refrigerator, a heat pipe and a heat switch assembly. The mechanical refrigerator has a first cooled stage and a second cooled stage. The heat pipe has a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly. The heat pipe is adapted to contain a condensable gaseous coolant when in use. The heat switch assembly comprises one or more gas gap heat switches, a first end coupled thermally to the second cooled stage and a second end coupled thermally to the target assembly. The cryogenic cooling system is adapted to be operated in a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage and wherein the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense. The target assembly is cooled by the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe during the heat pipe cooling mode. The cryogenic cooling system is further adapted to be operated in a gas gap cooling mode in which the temperature of the second cooled stage causes freezing of the coolant. The heat switch assembly is adapted to provide cooling from the second cooled stage to the target assembly during the gas gap cooling mode via the one or more gas gap heat switches.

First claim

The invention claimed is:

1. A cryogenic cooling system comprising:
a mechanical refrigerator having a first cooled stage and a second cooled stage, the second cooled stage being configured to reach a lower base temperature than the first cooled stage;
a heat pipe having a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly, the heat pipe being adapted to contain a condensable gaseous coolant; and
a heat switch assembly comprising one or more gas gap heat switches, the heat switch assembly having a first end coupled thermally to the second cooled stage and a second end coupled thermally to the target assembly.

2. The system according to claim 1 , further comprising a target refrigerator, wherein the target assembly comprises a cooling element of the target refrigerator, said cooling element being configured to reach a lower base temperature than the first cooled stage and the second cooled stage.

3. The system according to claim 2 , wherein the target refrigerator comprises a dilution refrigerator, the dilution refrigerator comprising a still, a cooled member and a mixing chamber, wherein the cooled member is arranged between the still and the mixing chamber, and wherein the mixing chamber forms the cooling element.

4. The system according to claim 3 , wherein the heat switch assembly comprises a first gas gap heat switch, a second gas gap heat switch and a third gas gap heat switch;
wherein the first gas gap heat switch is coupled thermally to the second cooled stage and the still, wherein the second gas gap heat switch is coupled thermally to the still and the cooled member, and wherein the third gas gap heat switch is coupled thermally to the cooled member and the mixing chamber.

5. The system according to claim 1 , further comprising a cooled member arranged between the second cooled stage and the target assembly;
wherein the heat switch assembly comprises a first gas gap heat switch coupled thermally to the second cooled stage and the cooled member, and a second gas gap heat switch coupled thermally to the cooled member and the target assembly.

6. The system according to claim 1 , wherein the cryogenic cooling system is adapted to be operated in a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage, and wherein the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense, whereby the target assembly is cooled by the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe;
wherein the cryogenic cooling system is further adapted to be operated in a gas gap cooling mode in which the temperature of the second cooled stage causes freezing of the coolant; and
wherein the heat switch assembly is adapted to provide cooling from the second cooled stage to the target assembly during the gas gap cooling mode via the one or more gas gap heat switches.

7. The system according to claim 6 , wherein the one or more gas gap heat switches are configured to contain a thermally conductive gas during the gas gap cooling mode.

8. The system according to claim 7 , wherein each of said gas gap heat switch comprises a stainless steel wall configured to contain the thermally conductive gas so as to cause thermal conduction across the switch.

9. The system according to claim 7 , wherein each of said gas gap heat switch comprises two elongate conductors aligned along a common major axis, wherein said elongate conductors are separated from each other by a gap configured to contain the thermally conductive gas during the gas gap cooling mode.

10. The system according to claim 7 , wherein the heat switch assembly is further configured to remove the thermally conductive gas from the one or more gas gap heat switches so as to substantially thermally isolate the second cooled stage from the target assembly.

11. A system according to claim 7 , further comprising a target refrigerator, wherein the target assembly comprises a cooling element of the target refrigerator, said cooling element being configured to reach a lower base temperature than the first cooled stage and the second cooled stage, and wherein the cryogenic cooling system is further adapted to be operated in a low temperature cooling mode in which the coolant is frozen, the thermally conductive gas is removed from the one or more gas gap heat switches and the target assembly is cooled by the cooling element so as to reach a lower temperature than the first cooled stage and the second cooled stage.

12. The system according to claim 1 , wherein the target assembly comprises a target apparatus provided as a docking station arranged to receive a sample carrier that supports a sample.

13. The system according to claim 1 , wherein the heat pipe comprises a housing defining an internal volume for containing the coolant, and which contains the first and second parts of the heat pipe in fluid communication with one another, wherein the housing comprises stainless steel.

14. The system according to claim 1 , wherein the condensable coolant for the heat pipe comprises neon.

15. The system according to claim 1 , wherein the mechanical refrigerator is selected from the group comprising: a pulse tube refrigerator, a Stirling refrigerator and a Gifford-McMahon refrigerator.

16. A method of operating a cryogenic cooling system, the cryogenic cooling system comprising a mechanical refrigerator having a first cooled stage and a second cooled stage, the second cooled stage being configured to reach a lower base temperature than the first cooled stage; a heat pipe having a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly, the heat pipe containing a condensable gaseous coolant, a heat switch assembly comprising one or more gas gap heat switches, the heat switch assembly having a first end coupled thermally to the second cooled stage of the mechanical refrigerator and a second end coupled thermally to the target assembly;
the method comprising the following steps:
i) causing the target assembly to adopt a temperature sufficient to ensure the coolant within the second part of the heat pipe is in the gaseous phase;
ii) operating the mechanical refrigerator to cause the second cooled stage to adopt a temperature which causes the coolant within the first part of the heat pipe to condense;
iii) cooling the target assembly during a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage by causing the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe; and
iv) cooling the target assembly during a gas gap cooling mode in which the temperature of the second cooled stage causes the coolant within the heat pipe to freeze, and wherein further cooling of the target assembly is applied by the second cooled stage via the one or more gas gap heat switches.

17. The method according to claim 16 , wherein the temperature of the second cooled stage is between 25 kelvin and 27 kelvin during the heat pipe cooling mode.

18. The method according to claim 16 , wherein the temperature of the second cooled stage is between 4 kelvin and 27 kelvin during the gas gap cooling mode.

19. The method according to claim 16 , wherein the target

Assignees

• Oxford Instruments Nanotechnology Tools Ltd

Inventors

• Matthews Anthony
• Patton Mark

Classifications

• F25B9/12

  using 3He-4He dilution · CPC title

• F25B9/145 Primary

  pulse-tube cycle · CPC title

• F25B23/006

  boiling cooling systems · CPC title

• F28F2013/008

  Variable conductance materials; Thermal switches · CPC title

• F25B25/005

  using primary and secondary systems · CPC title