Quench protection in superconducting magnets

Patent metadata

Field	Value
Publication number	US-2020091702-A1
Application number	US-201716470658-A
Country	US
Kind code	A1
Filing date	Dec 14, 2017
Priority date	Dec 21, 2016
Publication date	Mar 19, 2020
Grant date	—

Abstract

A toroidal field coil comprising a central column, a plurality of return limbs, a quench protection system, and a cooling system. The central column comprises IITS material. Each return limb comprises a quenchable section, two IITS sections, and a quenching 5 system. The quenchable section comprises superconducting material, and is configured to contribute towards a magnetic field of the toroidal field coil. The IITS sections comprise IITS material. The IITS sections electrically connect the quenchable section to the central column and are in series with the central column and the quenchable section. The quenching system is associated with the quenchable section 10 and configured to quench the quenchable section. The quench protection system is configured to detect quenches in the toroidal field coil and, in response to detection of a quench, cause the quenching system to quench the superconducting material in one or more of the quenchable sections in order to dump energy from the toroidal field coil into the one or more quenchable sections. The cooling system is configured to cool each 15 quenchable section to a temperature at which the superconducting material is superconducting. Each quenchable section has a heat capacity sufficient to cause a temperature of the quenchable section to remain below a first predetermined temperature when energy is dumped from the toroidal field coil into the quenchable section, and a resistivity sufficient to cause decay of the magnet's current quickly 20 enough that the temperature of the quenched part of the HTS section remains below a second predetermined temperature.

First claim

1 . A toroidal field coil comprising a central column comprising high temperature superconducting, HTS, material and a plurality of return limbs, each return limb comprising:
a quenchable section comprising superconducting material, the quenchable section being configured to contribute towards a magnetic field of the toroidal field coil; two high temperature superconducting, HTS, sections comprising HTS material, wherein the HTS sections electrically connect the quenchable section to the central column and are in series with the central column and the quenchable section; and a quenching system associated with the quenchable section and configured to quench the quenchable section;
the toroidal field coil further comprising:
a quench protection system configured to detect quenches in the toroidal field coil and, in response to detection of a quench, cause the quenching system to quench the superconducting material in one or more of the quenchable sections in order to dump energy from the toroidal field coil into the one or more quenchable sections;
a cooling system configured to cool each quenchable section to a temperature at which the superconducting material is superconducting;

wherein each quenchable section has a heat capacity sufficient to cause a temperature of the quenchable section to remain below a first predetermined temperature when energy is dumped from the toroidal field coil into the quenchable section, and a resistivity sufficient to cause decay of the magnet's current quickly enough that the temperature of the quenched part of the HTS section remains below a second predetermined temperature.

2 . A toroidal field coil according to claim 1 , wherein said first predetermined temperature is about 700 K or more preferably about 300 K.

3 . A toroidal field coil according to claim 1 or 2 , wherein said second predetermined temperature is about 300K, more preferably about 100K, more preferably about 50K.

4 . A toroidal field coil according to claim 1 , wherein each quenchable section further comprises a non-superconducting stabiliser.

5 . A toroidal field coil according to claim 4 , wherein the non-superconducting stabiliser comprises a metal having a ratio of resistivity to volumetric heat capacity greater than that of copper, such as stainless steel.

6 . A toroidal field coil according to claim 1 , wherein the HTS sections and the central column are cooled only by thermal contact with the quenchable sections.

7 . A toroidal field coil according to claim 1 , wherein the cooling system is further configured to cool the central column to a temperature at which the HTS material is superconducting.

8 . A toroidal field coil according to claim 1 , wherein each of the HTS and quenchable sections comprises a joint with copper elements electrically connected to the HTS or superconducting material, and wherein the HTS and quenchable sections are connected via the copper elements.

9 . A toroidal field coil according to claim 1 , wherein the quenchable sections comprise LTS material.

10 . A toroidal field coil according to claim 9 , wherein the cooling system is configured to cool the quenchable sections to 4.2K.

11 . A toroidal field coil according to claim 9 , wherein the cooling system is configured to cool the quenchable sections to a lower temperature than a temperature of the central column during operation of the toroidal field coil, such that the two HTS sections act as current leads having a temperature gradient along them.

12 . A toroidal field coil according to claim 9 , wherein each quenching system is configured to cause a quench by one of heating the LTS material or inducing alternating current losses in the LTS material.

13 . A toroidal field coil according to claim 1 , wherein the quenchable sections comprise HTS material and heaters laid adjacent to the HTS material, wherein the controller is configured to quench the superconducting material in the quenchable sections by causing the heaters to heat the HTS material.

14 . A toroidal field coil according to claim 13 , wherein the quenchable sections are constructed as stacks of type-0 pairs of HTS tapes, wherein each type-0 pair has a heater strip embedded in the copper between the HTS tapes.

15 . A toroidal field coil according to claim 14 , wherein the heater strips are connected such that current flow along adjacent heater strips is in opposite directions.

16 . A toroidal field coil according to claim 1 , wherein the quench detection system is configured to detect quenches in the central column and/or HTS sections.

17 . A toroidal field coil comprising a central column and a plurality of return limbs comprising turns of high temperature superconducting, HTS, material, the central column comprising:
a low temperature superconducting, LTS, core comprising LTS material, the LTS core being configured to contribute towards a magnetic field of the toroidal field coil; a high temperature superconducting, HTS, outer layer surrounding the LTS core and comprising HTS material; the LTS core being in series with at least some turns of the return limbs and comprising a quenching system configured to cause a quench in the LTS core;
the toroidal field coil further comprising:
a quench protection system configured to detect quenches in the return limbs or HTS outer layer and, in response to detection of a quench, cause the quenching system to quench the LTS material in the core in order to dump energy from the toroidal field coil into the LTS core;
a cooling system configured to cool the LTS core to a temperature at which the LTS material is superconducting;

wherein the LTS core has a heat capacity sufficient to cause a temperature of the LTS to remain below a first predetermined temperature when energy is dumped from the toroidal field coil into the LTS core, and a resistivity sufficient to cause decay of the magnet's current quickly enough that the temperature of the quenched part of the return limbs or HTS outer layer remains below a second predetermined temperature.

18 . A poloidal field coil assembly for use in a spherical tokamak, the poloidal field coil assembly comprising:
a first poloidal field coil comprising high temperature superconducting, HTS, material; a second poloidal field coil comprising low temperature superconducting, LTS, material and connected in series with the first poloidal field coil; a quenching system associated with the second poloidal field coil and configured to quench the second poloidal field coil; a quench protection system configured to detect quenches in the first poloidal field coil and, in response to detection of a quench, cause the quenching system to quench the second poloidal field coil in order to dump stored magnetic energy into the second poloidal field coil; a cooling system to cool the second poloidal field coil to a temperature at which the LTS material is superconducting; wherein the second poloidal field coil has a heat capacity sufficient to cause a temperature of the LTS to remain below a first predetermined temperature when energy is dumped into the second poloidal field coil, and a resistivity sufficient to cause decay of the magnet's current quickly enough that the temperature of the quenched part of the first poloidal field coil remains below a second predetermined temperature.

19 . A nuclear fusion reactor comprising a toroidal field coil assembly according to claim 1 .

20 . A nuclear fusion reactor according to claim 19 which reactor is a spher

Assignees

• Tokamak Energy Ltd

Inventors

• Noonan Paul
• Slade Robert

Classifications

• H02H7/001 Primary

  for superconducting apparatus, e.g. coils, lines, machines · CPC title

• G21B1/21

  Electric power supply systems, e.g. for magnet systems, switching devices, storage devices, circuit arrangements {(methods or means for discharging superconducting storage windings H01F6/003)} · CPC title

• H01F6/02 Primary

  Quenching; Protection arrangements during quenching {(protection circuits H02H7/001)} · CPC title

• G21B1/057 Primary

  Tokamaks · CPC title

• Y02E30/10

  Nuclear fusion reactors · CPC title