# US 11,114,230 B2 · Monitoring device for cryogenic device

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- Number: US 11,114,230 B2
- Document ID: US11114230B2
- Status: Granted
- Kind: B2
- Application number: 16/965,793
- Filed: 2019-01-30
- Published: 2020-12-31
- Granted: 2021-09-07
- Earliest claimed: 2018-01-30
- Assignees: Tokamak Energy Ltd
- Applicants: Tokamak Energy Ltd
- Inventors: Greg Brittles; Robert Slade; Marcel Kruip; Bas Van Nugteren
- Web page: https://patentgrep.com/patent/US11114230B2

## CPC

- H01F 6/02: Quenching; Protection arrangements during quenching {(protection circuits H02H7/001)}
- G01R 33/3815: with superconducting coils, e.g. power supply therefor
- H01F 6/06: Coils, e.g. winding, insulating, terminating or casing arrangements therefor
- H01F 41/048: {Superconductive coils}
- H02H 7/001: {for superconducting apparatus, e.g. coils, lines, machines}
- H10N 60/30: Devices switchable between superconducting and normal states
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A monitoring device for use in a cryogenic system. The monitoring device comprises first and second conducting elements and a current detector. The first conducting element comprises high temperature superconducting, HTS, material and is configured for connection to a current source and insertion into the cryogenic system. The second conducting element comprises HTS material and is connected in parallel to the first conducting element by first and second joints. The current detector is configured to detect a current in the second conducting element. When the HTS material in each of the first and second conducting elements is in a superconducting state, the resistance, RT, of the first conducting element between the first and second joints, is less than the sum, RB, of the resistance of the second conducting element between the first and second joints and the resistances of the first and second joints.

## Claims

### Claim 1

A monitoring device for use in a superconducting or cryogenic system, the monitoring device comprising:
a first conducting element comprising a high temperature superconducting, HTS, material and configured for connection to a current source and insertion into the superconducting or cryogenic system;
a second conducting element comprising a HTS material and connected in parallel to the first conducting element by first and second joints; and
a current detector configured to detect a current in the second conducting element;
wherein, when the HTS material in each of the first and second conducting elements is in a superconducting state, a resistance, RT, of the first conducting element between the first and second joints, is less than a sum, RB, of the resistance of the second conducting element between the first and second joints and the resistances of the first and second joints, RT<RB.

### Claim 2 (depends on 1)

The monitoring device according to claim 1, wherein the first and/or second conducting elements are arranged as one or more pairs of parallel elements, with the elements of each pair being adjacent to each other and configured to carry a current in opposite directions.

### Claim 3 (depends on 1)

The monitoring device according to claim 1, wherein the current detector comprises one or more of:
a conductive loop around the second conducting element;
a magnetic field detector;
a Hall probe; and
a strain gauge coupled to two sections of the second conducting element which carry the current in different directions.

### Claim 4 (depends on 1)

The monitoring device according to claim 1, and further comprising a current source configured to provide a current to the first conducting element.

### Claim 5 (depends on 4)

The monitoring device according to claim 4, wherein the current source is modulated to as to provide a periodic time-varying current.

### Claim 6 (depends on 5)

The monitoring device according to claim 5, wherein the current detector comprises a phase sensitive detector.

### Claim 7 (depends on 5)

The monitoring device according to claim 5, wherein the current detector is configured to measure a duty cycle of the current in the second conducting element.

### Claim 8 (depends on 4)

The monitoring device according to claim 4, wherein the current source is configured to provide a peak current of at least 80% of the critical current of a part of the HTS material of the first conducting element during normal operation of the superconducting or cryogenic system.

### Claim 9 (depends on 1)

The monitoring device according to claim 1, wherein the first and/or second conducting element comprise a HTS tape having an HTS layer.

### Claim 10 (depends on 9)

The monitoring device according to claim 9, wherein a width of the HTS layer varies within section of the first conducting element between the joints.

### Claim 11 (depends on 9)

The monitoring device according to claim 9, wherein the HTS layer is divided into a plurality of strips connected in series.

### Claim 12 (depends on 1)

The monitoring device according to claim 1, wherein the current detector is enclosed in a magnetic shield.

### Claim 13 (depends on 12)

The monitoring device according to claim 12, wherein the magnetic shield comprises a bulk superconductor.

### Claim 14 (depends on 13)

The monitoring device according to claim 13, further comprising a plurality of additional conducting elements comprising HTS material and connected in parallel to the first conducting element.

### Claim 15 (depends on 1)

The monitoring device according to claim 1, further comprising a third conducting element comprising a HTS material and connected in parallel to the first conducting element by third and fourth joints, wherein, when the HTS material in each of the first, second and third conducting elements is in a superconducting state, the resistance, RT, of the first conducting element between the first and second joints, is less than a sum, RB2, of the resistance of the third conducting element between the third and fourth joints and a resistances of the third and fourth joints, and the sum, RB2, of the resistance of the third conducting element between the third and fourth joints and the resistances of the third and fourth joints is less than the sum, RB, of the resistance of the second conducting element between the first and second joints and the resistances of the first and second joints RT<RB2<RB, and wherein a peak critical current of the HTS material of the third conducting element is less than a peak critical current of the HTS material of the first conducting element, and wherein the current detector is additionally configured to detect a current in the third conducting element.

### Claim 16 (depends on 1)

The monitoring device according to claim 1, wherein the second conducting element comprises a variable resistance.

### Claim 17 (depends on 16)

The monitoring device according to claim 16, wherein the variable resistance is one of:
a potentiometer;
a system for controllably causing the HTS material in the second conducting element to become normal; and
a joint or section of normal conducting material having a temperature-dependent resistance and a device for controlling the temperature thereof.

### Claim 18 (depends on 1)

The monitoring system comprising a plurality of monitoring devices according to claim 1 and a controller configured to monitor currents detected by each monitoring device.

### Claim 19 (depends on 18)

The monitoring system according to claim 18, wherein the controller is configured to identify reductions in critical currents of the first conducting elements of the monitoring devices on the basis of currents detected in the second conducting elements of the respective monitoring devices.

### Claim 20 (depends on 19)

The monitoring system according to claim 19, wherein the controller is configured to identify a cause of the reduction in critical current on the basis of the pattern of reductions in critical currents identified for the monitoring devices.

### Claim 21 (depends on 18)

The superconducting magnet comprising an HTS field coil and a monitoring device according to claim 18, wherein each first conducting element is located adjacent to the HTS field coil.

### Claim 22 (depends on 18)

The monitoring system according to claim 18, wherein the controller is configured to identify conditions likely to result in a quench on the basis of a rapid reduction in critical currents identified for one or more of the monitoring devices.

### Claim 23 (depends on 22)

The quench protection system for use in a superconducting magnet, the quench protection system comprising a monitoring system according to claim 22, and a system for dumping energy from a superconducting magnet, wherein the controller of the monitoring system is configured to trigger the system for dumping energy from the superconducting magnet in dependence upon identification of conditions likely to cause a quench.

### Claim 24 (depends on 18)

The monitoring system according to claim 18, wherein the monitoring devices are arranged in one or more pairs, each pair comprising a first and second monitoring device, wherein:
the first and second conducting elements of the first monitoring device are arranged adjacent to the respective first and second conducting elements of the second monitoring device; and
the first and second monitoring devices are arranged such that currents in the first conducting element of the each monitoring device flow in the same direction, and currents in the second conducting element of the each monitoring device flow in opposite directions.

### Claim 25 (depends on 18)

The monitoring system according to claim 18, wherein:
the monitoring devices are arranged in one or more sets, each set comprising monitoring devices having first conducting elements with differing patterns of measurement regions and non-measurement regions along the first conducting element;
the measurement regions having a reduced critical current compared to the non-measurement regions; and
the controller is configured to identify a location of conditions causing a reduction in critical current on the basis of detection of current on a subset of the monitoring devices of a set.

### Claim 26 (depends on 18)

The monitoring system according to claim 18, wherein the monitoring devices are connected in series.

### Claim 27 (depends on 18)

The monitoring system according to claim 18, wherein the monitoring devices are connected in parallel, each monitoring device being connected in series with a respective resistor having at least 10 times the total resistance of the monitoring device.

### Claim 28 (depends on 18)

The monitoring system according to claim 18, wherein the monitoring devices are arranged in one or more groups, the monitoring devices in each group being connected in series with a respective resistor having at least 10 times the total resistance of the monitoring devices of the group, and the groups being connected in parallel.

### Claim 29 (depends on 1)

The superconducting magnet comprising an HTS field coil and a monitoring device according to claim 1, wherein the first conducting element is located adjacent to the HTS field coil.

### Claim 30 (depends on 29)

The tokamak fusion reactor comprising a superconducting magnet according to claim 29, wherein the HTS field coil is one of a toroidal or poloidal field coil.

### Claim 31 (depends on 29)

The proton beam therapy, PBT, device comprising a superconducting magnet according to claim 29, wherein the HTS field coil is one of:
a field coil of an accelerator of the PBT device;
a dipole or quadrupole magnet of a proton beam steering system of the PBT device.