Cooling device with cryostat and cold head having reduced mechanical coupling

Patent metadata

Field	Value
Publication number	US-9982840-B2
Application number	US-201514855401-A
Country	US
Kind code	B2
Filing date	Sep 16, 2015
Priority date	Sep 30, 2014
Publication date	May 29, 2018
Grant date	May 29, 2018

Abstract

A cooling device ( 20 ) has a cryostat ( 23 ) and a cold head ( 1 ), in particular, the cold head ( 1 ) of a pulse tube cooler. The cryostat ( 23 ) has a vacuum container ( 4 ) with a vacuum container wall ( 4 a ), wherein the vacuum container wall ( 4 a ) seals off a vacuum inside the vacuum container ( 4 ) from the environment. A flexible sealing section ( 6 ) connects the vacuum container wall ( 4 a ) directly or indirectly to the room temperature part ( 1 a ) of the cold head ( 1 ). The flexible sealing section ( 6 ) seals off the inside of the cryocontainer ( 2 ) from the environment. The cooling device further reduces mechanical coupling between the cold head and the cryostat, in particular, in order to enable performance of NMR measurements with fewer disturbances due to external vibrations.

First claim

We claim:

1. A cooling device comprising:
a cold head or a cold head of a pulse tube cooler, said cold head having a room temperature part and a cooling arm; and
a cryostat having an access opening, said cryostat comprising:
a vacuum container having a vacuum container wall, wherein said vacuum container wall seals off a vacuum inside said vacuum container from an environment;
a cryocontainer disposed within said vacuum container, said cryocontainer structured to keep a cryogenic liquid and/or a cryogenic gas, said cryocontainer having a cryocontainer wall, wherein said cryocontainer wall seals off an inside of said cryocontainer from said vacuum of said vacuum container;
decoupling elements disposed between said room temperature part of said cold head and said vacuum container wall, thereby mounting said room temperature part to said vacuum container wall in a vibration-damped fashion, wherein said cooling arm of said cold head projects along a longitudinal axis through said access opening of said cryostat and into said cryocontainer; and
a flexible sealing section disposed between said vacuum container wall and said room temperature part, thereby directly or indirectly connecting said vacuum container wall to said room temperature part of said cold head, wherein said flexible sealing section seals off said inside of the cryocontainer from the environment.

2. The cooling device of claim 1 , wherein said cryocontainer is structured to contain liquid helium and gaseous helium at a pressure of between 950 mbar and 1100 mbar or of between 1015 mbar and 1050 mbar.

3. The cooling device of claim 1 , wherein said flexible sealing section connects a first mounting section on said vacuum container wall to a second mounting section on said room temperature part of said cold head, which are arranged at approximately a same level with respect to said longitudinal axis.

4. The cooling device of claim 1 , wherein said vacuum container wall is completely rigid.

5. The cooling device of claim 1 , wherein said flexible sealing section is formed by a plastic diaphragm of an elastomeric material or of rubber.

6. The cooling device of claim 1 , wherein said flexible sealing section is a rolling diaphragm.

7. The cooling device of claim 1 , further comprising a radiation shield disposed in said vacuum container between said vacuum container wall and said cryocontainer wall, wherein a cooling stage of said cooling arm is thermally coupled to said radiation shield, said cooling stage having a first coupling element with a first coupling surface and said radiation shield having a second coupling element with a second coupling surface, said first and said second coupling surfaces being located opposite to each other in said cryocontainer, such that a gap remains between said first and the second coupling element.

8. The cooling device of claim 7 , wherein, in order to increase thermal coupling, said first coupling surface has axial projections and/or recesses and said second coupling surface has mirror-inverted axial recesses and/or projections.

9. The cooling device of claim 8 , wherein said first coupling surface has an axially symmetrical toothing with annular, axial projections and recesses and said second coupling surface has a mirror-inverted axially symmetrical toothing with annular axial recesses and projections.

10. The cooling device of claim 9 , wherein said annular axial projections and recesses have a triangular shape in longitudinal section or a triangular shape with an angle of inclination relative to said longitudinal axis of between 10° and 30°.

11. The cooling device of claim 7 , wherein, when said cold head is not deflected, a gap width in a direction in which a separation between said first and the second coupling surface is minimum, is between 0.8 mm and 4.0 mm.

12. The cooling device of claim 1 , wherein said decoupling elements are loaded with said cold head and have an eigenfrequency f 0 , with f 0 ≤0.75 Hz or f 0 ≤0.5 Hz.

13. The cooling device of claim 1 , wherein said decoupling elements minimize excitation of said cryostat by said cold head in only two orthogonal directions perpendicular to said longitudinal axis, and further comprising a control valve connected to said cold head via a connecting line, wherein said connecting line is exclusively straight and perpendicular to said longitudinal axis.

14. The cooling device of claim 1 , wherein said decoupling elements minimize excitation of said cryostat by said cold head both in two orthogonal directions perpendicular to said longitudinal axis as well as movement of the cold head parallel to said longitudinal axis.

15. The cooling device of claim 14 , further comprising a compensation chamber disposed on said cooling device and delimited by a rigid wall part, a further flexible sealing section or a further rolling diaphragm, and a pressure plate held by of said flexible sealing section, wherein said rigid wall part is rigidly connected to said vacuum container wall of said cryostat and said pressure plate is mechanically coupled to said cold head along said longitudinal axis or is formed by said cold head, said pressure plate being disposed opposite a room temperature flange surface of said cold head which also seals said access opening and moreover further comprising a mechanism for adjusting a pressure in said compensation chamber in dependence on a pressure in the cryocontainer or for adjusting said pressure in said compensation chamber to be equal to said pressure in said cryocontainer.

16. The cooling device of claim 15 , wherein said mechanism for adjustment comprises a pressure compensation line which connects said cryocontainer to said compensation chamber.

17. The cooling device of claim 15 , wherein a surface of said pressure plate and a room temperature flange surface of said cold head are of substantially equal size and are arranged parallel to one another.

18. The cooling device of claim 15 , wherein said pressure plate is separate from said cold head and further comprising a rolling member or a rolling member formed by one or a plurality of bearing balls and disposed between said pressure plate and a rear side of said cold head.

19. The cooling device of claim 1 , further comprising a control valve and a connecting line disposed between said control valve and said cold head, said control valve being connected to said cold head at a contact point, wherein said contact point is spaced apart from a center of gravity of said cold head in a direction of said longitudinal axis facing away from said coupling element.

20. The cooling device of claim 1 , further comprising a radiation shield, wherein said cold head has a cooling stage and a further, colder cooling stage, wherein said cooling stage is substantially at a position of said radiation shield in a direction of said longitudinal axis and said further, colder cooling stage projects further into said cryocontainer than said cooling stage.

21. The cooling device of claim 1 , wherein said decoupling elements are designed as negative stiffness isolating elements.

22. A method for using the cooling device of claim 1 in an NMR measurement configuration, wherein the cryocontainer contains a magnet coil and a sample is located in a room temperature bore of said cryostat, wherein the sample is subjected to an NMR measurement or to an NMR measurement in which an NMR spectrum of the sample is recorded.

Assignees

• Bruker Biospin Gmbh

Inventors

• Wikus Patrick
• Bonn Steffen
• Harsch Heinrich

Classifications

• F25B9/145 Primary

  pulse-tube cycle · CPC title

• F25B2400/17

  Re-condensers · CPC title

• H01F6/04

  Cooling · CPC title

• F17C13/086

  for Dewar vessels or cryostats · CPC title

• G01R33/3815

  with superconducting coils, e.g. power supply therefor · CPC title