Magnet system for generation of a highly stable magnetic field

Patent metadata

Field	Value
Publication number	US-9620273-B2
Application number	US-201313967380-A
Country	US
Kind code	B2
Filing date	Aug 15, 2013
Priority date	Aug 31, 2012
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A magnet system generates a highly stable magnetic field at a sample location. The magnet system has a magnet cryostat housing a first superconducting magnet coil and a second magnet coil co-axial to the first magnet coil. The second magnet coil is short-circuited in a superconducting persistent mode during operation of the magnet system. An external power supply during operation supplies current to the first magnet coil via a current lead thereby generating a first magnetic field at the sample location that fluctuates according to the current noise of the power supply, wherein the second magnet coil is positioned and dimensioned in a way that it inductively couples to the first magnet coil such that it generates at the sample location a second magnetic field that compensates the fluctuations of the first magnetic field.

First claim

I claim:

1. A magnet system that generates a highly stable magnetic field at a sample location, the magnet system comprising:
a magnet cryostat housing a first superconducting magnet coil and a second magnet coil co-axial to said first magnet coil which second magnet coil is during operation of the magnet system short-circuited in a superconducting persistent mode; and
an external power supply that during operation supplies current to the first magnet coil via a current lead thereby generating a first magnetic field at the sample location that fluctuates according to a current noise of the power supply, wherein the second magnet coil is positioned and dimensioned in a way that it inductively couples to the first magnet coil such that it generates at the sample location a second magnetic field that compensates the fluctuations of the first magnetic field caused by the current noise of the power supply, wherein the first magnet coil and the second magnet coil are arranged on a common sample holder and the second magnet coil is arranged radially inside the first magnet coil and is axially shorter than the first magnet coil, the second magnet coil thereby having an inner radius which is smaller than an inner radius of the first magnet coil.

2. Magnet system according to claim 1 , wherein the second magnet coil is wound with an HTS conductor.

3. Magnet system according to claim 2 , wherein the HTS conductor is in the form of a slotted conductor tape, the slot extending between two ends of the tape thereby generating a continuous, closed superconducting current path, wherein two parts of the conductor tapes separated by the slot are wound to form the second magnet coil such that a superconducting persistent current follows the windings of both parts in the same sense of rotation.

4. Magnet system according to claim 1 , wherein the second magnet coil is wound with an LTS conductor.

5. Magnet system according to claim 1 , wherein the second magnet coil comprises several co-axial second partial coils which are separately or jointly superconductively short-circuited and which jointly compensate fluctuations of the first magnetic field at the sample location.

6. Magnet system according to claim 1 , wherein the first and the second magnet coil are co-axially surrounded by a superconductively short-circuited further magnet coil, wherein during operation, the further magnet coil generates a further magnetic field at the sample location, which is larger than the first magnetic field and wherein a presence of the further magnet coil is taken into account for positioning und dimensioning of the second superconducting magnet coil.

7. Magnet system according to claim 6 , wherein during operation, at least the further magnet coil or a partial coil of the further magnet coil carries a superconducting persistent current with a reversed sense of rotation with respect to the current through the first magnet coil, in such a way that a stray field of the magnet system is further reduced compared to a stray field of a magnet system without a reversed further magnet coil or further partial magnet coil.

8. Magnet system according to claim 6 , wherein the second magnet coil or a partial coil of the second magnet coil is wound with a conductor that at temperatures and magnetic field existing at its operating position, has critical current strengths which are below a persistent current strength of the further magnet coil.

9. Magnet system according to claim 6 , wherein the second magnet coil or a partial coil of the second magnet coil is wound with a conductor that at temperatures and magnetic field existing at its operating position, has critical current strengths which are below a persistent current strength of the further magnet coil and wherein the second magnet coil or a partial coil of the second magnet coil is wound with a conductor that at temperatures and magnetic field existing at its operating position, has critical current strengths which are below a current strength supplied by the power supply, and wherein, apart from an induced compensation current, the second magnet coil carries essentially no current during operation.

10. Nuclear magnetic resonance spectrometer with the magnet system according to claim 9 .

11. Magnet system according to claim 1 , wherein the second magnet coil or a partial coil of the second magnet coil is wound with a conductor that at temperatures and magnetic field existing at its operating position, has critical current strengths which are below the current strength supplied by the power supply.

12. Magnet system according to claim 1 , wherein, apart from an induced compensation current, the second magnet coil carries essentially no current during operation.

13. Magnet system according to claim 1 , wherein the second magnet coil is single-layered.

14. Magnet system according to claim 1 , wherein, during operation and at the sample location, the magnet system generates a magnetic field larger than 23.5 Tesla.

15. Magnet system according to claim 1 , wherein the first and second superconducting magnet coils are in a lower part of a helium tank of the magnet cryostat below a thermal barrier and, during operation, have a temperature below 4 K and the current lead to the power supply is guided through an upper part of the helium tank above the thermal barrier with a temperature above 4 K.

16. Magnet system according to claim 1 , wherein for the positioning and dimensioning of the second superconducting magnet coil the presence of all during operation superconductively short-circuited current loops of the magnet system are taken into account.

17. Magnet system according to claim 16 , wherein for the positioning and dimensioning of the second superconducting magnet coil the presence of highly conductive structures within the magnet system is also taken into account.

18. Nuclear magnetic resonance spectrometer with the magnet system according to claim 1 .

Assignees

• Bruker Biospin Gmbh

Inventors

• Kasten Arne

Classifications

• G01R33/421

  of main or gradient magnetic field · CPC title

• G01R33/44

  using nuclear magnetic resonance [NMR] (G01R33/24, G01R33/62 take precedence) · CPC title

• H01F6/06 Primary

  Coils, e.g. winding, insulating, terminating or casing arrangements therefor · CPC title

• G01R33/3875 Primary

  using correction coil assemblies, e.g. active shimming · CPC title

• G01R33/3815

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