Method for charging a superconductor magnet system, with a main superconductor bulk magnet and a shield superconductor bulk magnet

Patent metadata

Field	Value
Publication number	US-11527343-B2
Application number	US-202017085314-A
Country	US
Kind code	B2
Filing date	Oct 30, 2020
Priority date	Nov 14, 2019
Publication date	Dec 13, 2022
Grant date	Dec 13, 2022

Abstract

Charging method for a superconductor magnet system with reduced stray field, weight and space includes: arranging the system within a charger magnet bore; with T main >T main crit and T shield >T shield crit , applying a current I charger to the charger magnet and increasing I charger to a first current I 1 >0; lowering a main superconductor bulk magnet temperature T main to an operation temperature T main op , with T main op <T main crit , while keeping T shield >T shield crit ; lowering I charger to a second current I 2 <0, thereby inducing a persistent current IP main in the main magnet; lowering a shield magnet temperature T shield to an operation temperature T shield op , with T shield op <T shield crit ; increasing I charger to zero, thereby inducing a persistent current IP shield in the shield magnet; removing the magnet system from the charger bore, and keeping T main ≤T main op with T main op <T main crit and T shield ≤T shield op with T shield op <T shield crit ; where: T main crit : main magnet critical temperature and T shield crit : shield magnet critical temperature.

First claim

What is claimed is:

1. Method for charging a superconductor magnet system,
the superconductor magnet system comprising
a main superconductor bulk magnet defining a main bulk bore,
a shield superconductor bulk magnet defining a shield bulk bore, and
a cryostat system having a room temperature bore,
wherein the cryostat system contains the main superconductor bulk magnet and the shield superconductor bulk magnet,
wherein the shield superconductor bulk magnet radially surrounds the main superconductor bulk magnet such that the main bulk bore lies radially within the shield bulk bore, and
wherein the main superconductor bulk magnet and the shield superconductor bulk magnet are arranged coaxially with the room temperature bore such that the room temperature bore lies radially within the main bulk bore,

the method comprising:
step a) arranging the superconductor magnet system at least partially within a charger bore of a charger magnet;
step b) with T main >T main crit and T shield >T shield crit applying an electrical current I charger to the charger magnet and increasing I charger to a first current I 1 >0,
step c) lowering T main to or below an operation temperature T main op of the main superconductor bulk magnet, with T main op <T main crit , while keeping T shield >T shield crit ;
step d) lowering I charger to a second current I 2 <0, wherein a main persistent current IP main is induced in the main superconductor bulk magnet, which stays below a critical current of the main superconductor bulk magnet at T main , with T main ≤T main op ;
step e) lowering T shield to or below an operation temperature T shield op of the shield superconductor bulk magnet, with T shield op <T shield crit :
step f) increasing I charger to zero, wherein a shield persistent current IP shield is induced in the shield superconductor bulk magnet, which stays below a critical current of the shield superconductor bulk magnet at T shield , with T shield ≤T shield op ;
step g) removing the superconductor magnet system from the charger bore of the charger magnet, and keeping T main at or below T main op withT main op <T main crit as well as T shield at or below T shield op , with T shield op <T shield crit , with T main : temperature of the main superconductor bulk magnet;
T main crit : critical temperature of the main superconductor bulk magnet;
T shield : temperature of the shield superconductor bulk magnet; and
T shield : critical temperature of the shield superconductor bulk magnet,
wherein the temperatures T main T shield are set to different values during the steps c) and d), and
wherein the main superconductor bulk magnet and the shield superconductor bulk magnet are, at least temporarily, substantially thermally decoupled during the charging method.

2. Method according to claim 1 , wherein the charger bore is arranged coaxially with the room temperature bore of the cryostat system in the step a).

3. Method according to claim 1 , wherein
|I 2 /I 1 |≤0.33.

4. Method according to claim 1 , wherein
0.7≤|I 1 /I 2 |*|R main 2 /R shield 2 |≤1.4,
with R main : average radius of the main superconductor bulk magnet; and
R shield : average radius of the shield superconductor bulk magnet.

5. Method according to claim 1 , wherein
T main op ≤0.75*T main crit and T shield op ≤0.75*T shield crit .

6. Method according to claim 1 , wherein
the cryostat system comprises a normal cryocooler and thermal connections of the normal cryocooler to a main bulk thermal stage connected to the main superconductor bulk magnet and to a shield bulk thermal stage connected to the shield superconductor bulk magnet,
during the step c) and the step d), a shield thermal switch in the thermal connection to the shield bulk thermal stage is kept open, and
during the step e) and after the step e), the shield thermal switch is kept closed.

7. Method according to claim 1 , wherein
at least during the steps c) through f), the cryostat system is equipped with an auxiliary cryocooler,
during the steps c) through f), cooling power of the auxiliary cryocooler is directed to a main bulk thermal stage connected to the main superconductor bulk magnet,
during the steps e) and f), cooling power of the auxiliary cryocooler is directed to a shield bulk thermal stage connected to the shield superconductor bulk magnet,
after the step f), the auxiliary cryocooler is removed from the cryostat system,
and the cryostat system comprises a normal cryocooler and thermal connections of the normal cryocooler to the main bulk thermal stage and to the shield bulk thermal stage,
and after the step f), the normal cryocooler provides cooling power to the main bulk thermal stage and to the shield bulk thermal stage.

8. Method according to claim 7 , wherein the normal cryocooler provides cooling power to the main bulk thermal stage and to the shield bulk thermal stage only after the step f).

9. Method according to claim 7 , wherein
the thermal connection between the normal cryocooler and the main bulk thermal stage and/or the thermal connection between the normal cryocooler and the shield bulk thermal stage include/includes a weak thermal link or a thermal switch, and
the weak thermal link or the thermal switch slows down or blocks heat conduction between the normal cryocooler and the main bulk thermal stage and/or between the normal cryocooler and the shield bulk thermal stage during at least some of the step c), the step d), the step e) and/or the step f).

10. Method according to claim 1 , wherein
the cryostat system includes two normal cryocoolers, with a first of the normal cryocoolers having a thermal connection to a main bulk thermal stage connected to the main superconductor bulk magnet, and a second of the normal cryocoolers having a thermal connection to a shield bulk thermal stage connected to the shield superconductor bulk magnet, and
the first normal cryocooler provides cooling power to the main bulk thermal stage beginning with the step c), and the second normal cryocooler provides cooling power to the shield bulk thermal stage beginning with the step e).

Assignees

• Bruker Switzerland Ag

Inventors

• March Stephen Alfred
• Hinderer Joerg
• Heiss Stephan

Classifications

• H01F6/00

  Superconducting magnets; Superconducting coils {(magnetic resonance assemblies using superconducting coil systems G01R33/3815)} · CPC title

• H01F6/04 Primary

  Cooling · CPC title

• H01F6/008 Primary

  Electric circuit arrangements for energising superconductive electromagnets · CPC title

• H01F27/36

  Electric or magnetic shields or screens (movable for varying inductance H01F21/10) · CPC title

• H01F13/003

  Methods and devices for magnetising permanent magnets (permanent magnets H01F7/02) · CPC title