Cryogenic cooling apparatus and method such as for magnetic resonance imaging systems

Patent metadata

Field	Value
Publication number	US-10258253-B2
Application number	US-201314415519-A
Country	US
Kind code	B2
Filing date	Apr 19, 2013
Priority date	Jul 19, 2012
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

A cryogenic cooling apparatus comprises a supply gas line and a return gas line adapted to be coupled to a compressor. A coupling element is positioned in gaseous communication with the supply and return gas lines, the coupling element being adapted in use to supply gas to a mechanical refrigerator so that the pressure of said supplied gas is modulated by the coupling element in a cyclical manner. A sensing system is used to monitor the operational state of the mechanical refrigerator and a control system modulates the frequency of the cyclical gas pressure supplied by the coupling element in accordance with the monitored operational state. The mechanical refrigerator has a first cooled stage and a second cooled stage, the second cooled stage being adapted to be coupled thermally with target apparatus to be cooled. A selectively coupleable thermal link is provided for thermally coupling the first cooled stage of the mechanical refrigerator to the second cooled stage in dependence upon the operational state of the mechanical refrigerator. A method of use of the apparatus is also disclosed. The apparatus and method have particular application in a Magnetic Resonance Imaging system.

First claim

The invention claimed is:

1. A cryogenic cooling apparatus comprising:
a supply gas line and a return gas line adapted to be coupled to a compressor when in use;
a coupling element in gaseous communication with the supply and return gas lines, the coupling element being adapted in use to supply gas to a mechanical refrigerator, the pressure of said supplied gas being modulated by the coupling element in a cyclical manner;
a sensing system adapted to monitor the operational state of the mechanical refrigerator when in use; and,
a control system adapted to modulate the frequency of a cyclical gas pressure supplied by the coupling element in accordance with the monitored operational state;

wherein the mechanical refrigerator comprises:
a first cooled stage and a second cooled stage, the second cooled stage being adapted to be coupled thermally with a target apparatus to be cooled; and,
a selectively coupleable thermal link in the form of a heat pipe for thermally coupling the first cooled stage of the mechanical refrigerator to the second cooled stage in dependence upon the operational state of the mechanical refrigerator;
wherein the heat pipe has a first part coupled thermally to the first stage of the mechanical refrigerator and a second part coupled thermally to the second stage of the mechanical refrigerator, the heat pipe being adapted to contain a condensable gaseous coolant when in use;
the cryogenic cooling apparatus being adapted in use to be operated in a first cooling mode in which the temperature of the cooled member causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the first stage causes the coolant in the first part to condense, whereby the cooled member is cooled by the movement of the condensed liquid from the first part to the second part of the heat pipe;
wherein the sensing system is configured to detect when the apparatus is in the first cooling mode and wherein the control system is further adapted to modulate the frequency of the cyclical gas pressure during a cool down procedure in response to the sensing system detecting that the first cooling mode has begun, wherein the modulation reduces the cooling power of the first cooled stage so as to prolong the first cooling mode.

2. Apparatus according to claim 1 , wherein the sensing system comprises a pressure sensing apparatus adapted to monitor the pressure in at least one of the supply and return gas lines.

3. Apparatus according to claim 1 , wherein the apparatus further comprises a temperature sensing apparatus for monitoring a temperature within a cooled region of the mechanical refrigerator and wherein the control system is further adapted to control the frequency of the cyclical gas pressure in accordance with the temperature monitored by the temperature sensing apparatus.

4. Apparatus according to claim 1 , wherein the sensing system comprises a temperature sensing apparatus adapted to monitor the temperature in one or more of the first cooled stage, the second cooled stage or the thermal link.

5. Apparatus according to claim 1 , wherein the modulation increases the cooling power of the second cooled stage.

6. Apparatus according to claim 1 , wherein the thermal link is arranged to be operable under the control of the control system.

7. Apparatus according to claim 1 , wherein the modulation reduces the rate of cooling of the first cooled stage during the first cooling mode.

8. Apparatus according to claim 1 , wherein the apparatus is further adapted in use to be operated in an second cooling mode in which the temperature of the first cooled stage causes the freezing of the coolant at the first part and causes the temperature of the second cooled stage to then become lower than the temperature of the first cooled stage.

9. Apparatus according to claim 8 , wherein the sensing system is configured to detect when the second cooling mode has begun and wherein the control system is configured to modulate the frequency of the cyclical gas pressure in response to the sensing system detecting that the first cooling mode has ended and the second cooling mode has begun.

10. Apparatus according to claim 1 , wherein the sensing system comprises a thermocouple configured to monitor the temperature of the heat pipe in order to detect when the apparatus is in the first cooling mode.

11. Apparatus according to claim 9 , wherein the control system comprises a heater in thermal communication with the heat pipe for use in controlling the environment in the heat pipe.

12. Apparatus according to claim 1 , further comprising a coolant gas or mixture of gases sealed within the heat pipe.

13. Apparatus according to claim 12 , wherein the coolant comprises one or more gases selected from the group of: Nitrogen, Oxygen, Xenon, Argon, Krypton, Carbon Dioxide, Hydrogen.

14. Apparatus according to claim 1 , further comprising an external volume in fluid communication with the interior of the heat pipe.

15. Apparatus according to claim 1 , wherein the heat pipe comprises an internal volume for containing the coolant, and which contains the first and second parts in fluid communication with one another.

16. Apparatus according to claim 1 , wherein the heat pipe comprises walls within which are positioned bellows so as to act as a vibration-dampening mechanism.

17. Apparatus according to claim 1 , wherein the heat pipe may further comprise an anti-radiation member operative to reduce the passage of electromagnetic radiation between the first and second parts, the anti-radiation member being arranged to allow passage of liquid from one side of the member to the opposing side.

18. Apparatus according to claim 1 wherein the mechanical refrigerator comprises an additional cooled stage, the additional stage being either an intermediate stage between the first and second stages, or being a third stage.

19. Apparatus according to claim 1 , further comprising target apparatus, thermally coupled to the stage of the refrigerator which is capable of attaining the lowest operational temperature, the thermal coupling being through a high thermal conductivity member.

20. Apparatus according to claim 1 , wherein the coupling element comprises a rotary valve.

21. Apparatus according to claim 1 , wherein the coupling element is driven by a motor and wherein the control system is further adapted to control the speed of the motor.

22. Apparatus according to claim 1 , wherein the mechanical refrigerator is selected from the group of: a pulse tube refrigerator, a Gifford-McMahon refrigerator, a Stirling refrigerator.

23. Use of an apparatus according to claim 1 in providing cooling for a magnetic resonance system.

24. Apparatus according to claim 1 , wherein said compressor is in gaseous communication with the supply and return gas lines.

25. A system according to claim 24 , wherein the compressor is selected from the group of a: scroll compressor, rotary screw compressor, rotary vane compressor, rotary lube compressor or diaphragm compressor.

26. Use of a cryogenic cooling system according to claim 24 in providing cooling for a magnetic resonance system.

27. A magnetic resonance system comprising:
a magnet system comprising a number of magnets for generating a magnetic field which is suitable for obtaining magnetic resonance signals from a target region;
a radio frequency system for obtaining radi

Assignees

• Oxford Instruments Nanotechnology Tools Ltd

Inventors

• Garside John

Classifications

• F25B9/10 Primary

  with several cooling stages · CPC title

• F25B49/022

  Compressor control arrangements · CPC title

• F25B9/145

  pulse-tube cycle · CPC title

• A61B5/055 Primary

  involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging · CPC title

• F25D19/006

  Thermal coupling structure or interface · CPC title