Partial insulation with diagnostic pick-up coil

Abstract

A partially insulating layer for an HTS field coil. The partially insulating layer includes an insulator having a set of linking tracks and a set of pickup tracks therein. Each linking track is electrically conductive and electrically connected to a first surface and a second surface of the partially insulating layer to provide an electrical path between the first surface and the second surface. Each pickup track is electrically conductive and inductively coupled to a corresponding linking track and electrically insulated from the first surface and the second surface. Each pickup track is configured to be connected to a current measuring device to measure a current induced in the pickup track due to a change in current flow in the corresponding linking track.

Description

Technical Field

[0001] The present invention relates to a high temperature superconducting (HTS) magnet. In particular, the present invention relates to a partially insulating layer for a partially insulated HTS magnet. Background Art

[0002] Superconducting materials are usually divided into "high temperature superconductors" (HTS) and "low temperature superconductors" (LTS). LTS materials (such as Nb and NbTi) are metals or metal alloys whose superconductivity can be described by the BCS theory. The critical temperature (the temperature above which the material cannot superconduct even in zero magnetic field) of all low temperature superconductors is below about 30 K. The BCS theory does not describe the properties of HTS materials, and such materials may have critical temperatures above about 30 K (although it should be noted that physical differences in composition and superconducting operation - not critical temperature - define HTS and LTS materials). The most commonly used HTS are "cuprate superconductors" - ceramics based on cuprates (compounds containing copper oxide groups), such as BSCCO or ReBCO (where Re is a rare earth element, usually Y or Gd). Other HTS materials include iron phosphorus (such as FeAs and FeSe) and magnesium diboride (MgB2).

[0003] ReBCO is usually manufactured as strips with Figure 1 The structure shown. Such a strip 100 is typically about 100 microns thick and comprises a substrate 101 (typically about 50 microns thick electropolished Hastelloy) on which is deposited by IBAD, magnetron sputtering or other suitable technique a series of buffer layers called buffer stack 102 of about 0.2 microns thickness. An epitaxial ReBCO-HTS layer 103 (deposited by MOCVD or other suitable technique) covers the buffer stack and is typically 1 micron thick. A 1 to 2 micron silver layer 104 is deposited on the HTS layer by sputtering or other suitable technique, and a copper stabilizer layer 105 is deposited on the strip by electroplating or other suitable technique, typically completely encapsulating the strip.

[0004] The substrate 101 provides a mechanical support that can be supplied through a production line and allows the growth of subsequent layers. The buffer stack 102 is required to provide a biaxially textured crystal template on which to grow the HTS layers and to prevent chemical diffusion of elements from the substrate into the HTS, which would compromise its superconducting properties. The silver layer 104 is required to provide a low resistance interface from the ReBCO to the stabilizer layer, and the stabilizer layer 105 provides an alternative current path in the event that any part of the ReBCO stops superconducting (enters a "normal" state).

[0005] Additionally, it is possible to produce "peel-off" HTS tapes that have no substrate and buffer stack, but instead have silver layers on both sides of the HTS layer. The tapes with substrates will be referred to as "backed" HTS tapes.

[0006] HTS tapes can be arranged into HTS cables. HTS cables include one or more HTS tapes connected along their length by conductive material (usually copper). HTS tapes can be stacked (i.e. arranged so that the HTS layers are parallel), or the HTS tapes can have some other arrangement of tapes, where the tapes can vary along the length of the cable. Notable special cases of HTS cables are single HTS tapes and HTS pairs. HTS pairs include a pair of HTS tapes arranged so that the HTS layers are parallel. In the case of using backed tapes, the HTS pairing can be type 0 (HTS layers facing each other), type 1 (HTS layer of one tape facing the substrate of another tape), or type 2 (substrates facing each other). Cables including more than 2 tapes can arrange some or all of the tapes into HTS pairs. Stacked HTS tapes can include various arrangements of HTS pairs, the most common being a stack of type 1 pairs or a stack of type 0 pairs and (or equivalently) a stack of type 2 pairs. HTS cables can include a mixture of backed tapes and peel-away tapes.

[0007] Superconducting magnets are formed by arranging HTS cables (or individual HTS tapes, which for illustration purposes may be considered single-tape cables) into coils or by winding HTS cables or by providing sections of coils made of HTS cables and splicing the sections together. HTS coils fall into three main categories:

[0008] • Insulated HTS coils, which have electrical insulation between the turns (so that current can only flow through the HTS cable in a “helical path”).

[0009] • Uninsulated HTS coils, where the turns are connected radially and along the cable (e.g. by connecting the copper stabilization layer of the HTS cable).

[0010] • Partially insulated HTS coils, in which the turns are radially connected with controlled resistance, either by using a material with high electrical resistance (eg compared to copper) or by providing intermittent insulation between the coils.

[0011] An uninsulated coil can also be viewed as a low resistance version of a partially insulated coil.

[0012] Having no or partial insulation between turns slows down the rate of temperature rise of local "hot spots" (normal areas). The growth rate (spatial propagation) of the normal (resistive HTS) areas in an HTS magnet depends on many parameters, but is typically less than 100 mm / s in the axial direction (i.e. along the cable) and about 2 to 100 times slower in the transverse direction (i.e. between adjacent turns). The exact propagation rate of the normal areas in each direction depends on the thermal and electrical properties of the materials used and the cable construction. In particular, the rate of transverse propagation is affected by the thermal properties of the materials between the turns.

[0013] In large magnets (linear dimensions in meters, and where the coil cross-sectional dimensions are small (i.e., about 10 times smaller) than the largest total coil dimension), lateral propagation causes the entire cross-section of the coil to become normal in a region covering a small portion of the periphery of the coil, causing the total current of all turns to flow only in the metallic stabilizer within the normal cross-section. Outside the normal region, the conductor remains superconducting. Outside the normal region, the conductor remains superconducting. The resistance of this normal region is not sufficient to cause the magnet's current to drop rapidly, but rather causes the stored magnetic energy of the entire magnet to be transferred into this small normal (resistive) volume that grows only slowly around the periphery of the coil. Unless this condition is detected quickly so that the magnet's stored energy can be transferred into the resistance outside the coil, the temperature of the normal region will rise very rapidly, which is likely to cause significant damage to the conductor within the normal region.

[0014] One application of HTS magnets is in tokamak fusion reactors and plasma chambers, especially in spherical tokamaks. Tokamaks have two sets of magnets - poloidal field coils, which are aligned to generate a poloidal field and are usually circular, and toroidal field coils, which include a central post and multiple return arms and are arranged to generate a toroidal field. HTS magnets can be used for either set of field coils, but are particularly useful for toroidal field coils in small tokamaks because such field coils have severe space constraints, which the increased current density and / or reduced cooling requirements of HTS can significantly help with.

[0015] Another possible application of HTS magnets is in proton beam therapy devices. Proton beam therapy (PBT, also called proton therapy) is a type of particle therapy used in the treatment of cancer (and other conditions that respond to radiation therapy). In PBT, a beam of protons is directed at the treatment site (e.g., a tumor).

[0016] Another similar treatment is proton boron capture therapy (PBCT), in which boron-11 is introduced to the target site and a proton beam is used to initiate p+ 11 B→3α reaction. The same equipment can be used to provide a proton beam for PBT or PBCT.

[0017] Proton beams used for PBT and PBCT are generated by particle accelerators such as cyclotrons or linear accelerators. Accelerators commonly used for PBT and PBCT typically generate protons with energies in the range of 60 to 250 MeV, with the most powerful facilities currently in operation having a maximum energy of 400 MeV.

[0018] The design of a PBT or PBCT device requires a gantry to hold the electromagnets that guide the protons at the beam energy. This requires very high magnetic fields, so using HTS magnets can greatly reduce the mass and size of the electromagnets and the gantry required to move them. HTS magnets can be used in the accelerator, the quadrupole magnets of the guide magnets, or the dipole magnets of the guide magnets. Summary of the invention

[0019] According to a first aspect, a partially insulating layer for an HTS magnet coil is provided. The partially insulating layer includes an insulator having a set of linking tracks and a set of pickup tracks therein. Each linking track is electrically conductive and electrically connected to a first surface and a second surface of the partially insulating layer so as to provide an electrical path between the first surface and the second surface. Each pickup track is electrically conductive and inductively coupled to a corresponding linking track and is electrically insulated from the first surface and the second surface. Each pickup track is configured to be connected to a current measuring device so as to measure a current induced in the pickup track due to a change in current flowing in the corresponding linking track.

[0020] According to a second aspect, a partial insulating layer for an HTS magnet coil is provided. The partial insulating layer includes an insulator having a set of linking tracks and a set of pickup tracks therein. Each linking track is electrically conductive and electrically connected to a first surface and a second surface of the partial insulating layer to provide an electrical path between the first surface and the second surface. The pickup track is electrically conductive, extends along the length of the partial insulating layer, and is electrically insulated from the first surface and the second surface. The pickup track is configured to be connected to a voltage measuring device to measure a voltage induced in the pickup track due to a change in current in the HTS conductor of the HTS magnet coil.

[0021] According to a third aspect, a high temperature superconducting (HTS) field coil is provided, comprising one or more HTS cables and one or more partial insulation layers, wherein the one or more HTS cables are arranged to form turns and the one or more partial insulation layers are arranged to radially connect the turns, wherein the partial insulation layers are partial insulation layers according to the first or second aspect.

[0022] According to a fourth aspect, a tokamak is provided, comprising toroidal field coils as HTS field coils according to the third aspect.

[0023] According to a fifth aspect, there is provided a proton beam therapy (PBT) apparatus comprising the HTS field coil according to the third aspect, wherein the HTS field coil is one of the following:

[0024] Field coils of the accelerator of the PBT device;

[0025] Dipole or quadrupole magnets of the proton beam guidance system of a PBT device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of HTS strip;

[0027] Figures 2A to 2E A portion of the insulation layer of the HTS coil is shown;

[0028] Figure 3 A circuit diagram illustrating the principle of an exemplary partial insulating layer is shown;

[0029] Figures 4A to 4F An exemplary partial insulation layer is shown;

[0030] Figure 5 An alternative coil configuration is shown;

[0031] Fig. 6A and 6B Another alternative coil configuration is shown; and

[0032] Fig. 7A and 7B An alternative configuration of a portion of the insulating layer is shown. DETAILED DESCRIPTION

[0033] Figures 2A to 2E Shown is a partial insulation layer that may be applied between HTS cables to radially connect the HTS cables.

[0034] The partial insulation layer includes 5 layers, which are:

[0035] • a first metal connection layer 211;

[0036] • a first insulating layer 221;

[0037] • a conductive layer 230;

[0038] • a second insulating layer 222;

[0039] • A second metal connection layer 212.

[0040] Figures 2C to 2E The layouts of the first metal connection layer 211 , the conductive layer 230 , and the second metal connection layer 212 are shown respectively. Figure 2A and 2B is along Figures 2C to 2E A cross section of lines A and B.

[0041] The connection layer is present to provide a better electrical connection to the HTS cable (either by soldering or direct contact).

[0042] The conductive layer is divided into several conductive areas. These areas are of two types. The square areas 231 (although they can be of any shape in practice) are connected to only one of the metal connection layers through conductive links 206. These areas do not affect the electrical properties of the partial insulating layers, but provide a thermal path through the corresponding insulating layers. By changing the size of these areas and the number of connectors between these areas and the metal connection layers, the thermal properties of the partial insulating layers can be changed independently of the electrical properties.

[0043] The other regions 232 are connected to the first metal connection layer 211 and the second metal connection layer 212 via the windows 201 and 202 in the first insulating layer 221 and the second insulating layer 222, respectively. The resistance between the windows can be controlled by changing the geometry of the region 232 - for example, in the region 232, the first metal connection layer 211 is connected to the second metal connection layer 212 via the windows 201 and 202 in the first insulating layer 221 and the second insulating layer 222. Figure 2D In the case of the elongated track 233 shown, increasing the width of the track will reduce the resistance between the windows, and increasing the length of the track (e.g. by providing a non-linear track, or by moving the windows) will increase the resistance between the windows. The resistance of the entire section of the insulating layer can be controlled by varying the resistance of each connector between the windows and by varying the number of such connectors along the section of the insulating layer.

[0044] The window 201 in the first insulating layer is formed by drilling a hole through the first connection layer and the first insulating layer, and then the drilled hole is plated with metal 203 (or other conductive material) to connect the first connection layer 211 and the conductive layer 230. The window 202 in the second insulating layer is formed by drilling a hole through all layers, and then the hole is plated with metal 204 (or other conductive material). In order to prevent the window 202 through the second insulating layer from forming a connection with the first connection layer, the first connection layer is etched around the window 202 to electrically insulate it, and an insulating cap 205 is placed at the end of the window 202 to ensure that no bridging occurs due to welding or contact with the HTS cable.

[0045] As an alternative, the window 202 can be drilled from the other side of the partial insulating layer instead, so that the window 202 passes through the second connection layer, the second insulating layer and the conductive layer, and does not pass through (or does not completely pass through) the first insulating layer. As another alternative, all windows can be formed by holes passing through all layers, and the second connection layer and the insulating cap on the second connection layer are etched for the window 201 of the first insulating layer.

[0046] Implementations and related examples are further described in co-pending application PCT / GB2019 / 050275.

[0047] The use of partial insulation will significantly extend the time available for detecting a quench compared to an equivalent uninsulated coil. However, there is still a need for a quench detection method that is fast enough to detect hot spots forming in the coil in time so that countermeasures can be applied before magnet damage becomes inevitable.

[0048] When the current in the HTS cable of the coil section approaches the critical current of the HTS cable, some current will leave the HTS and start flowing through the stabilizer layer of the cable. At this point, the current will start flowing through the resistive and inductive links that form the section insulation between the HTS turns. The section insulation made of PCB helps to accurately lay out and design the link tracks, allowing accurate setting of the turn-to-turn resistance and link track inductance.

[0049] The present disclosure focuses on detecting this current flow, and using this detection to detect when current sharing begins to occur in an HTS magnet. Detection of this current sharing pattern can be used as an early warning of a quench (or a possible quench - as used herein, "quench detection" includes the detection of an impending quench or a condition that is likely to result in a quench).

[0050] Principle Figure 3 As shown, Figure 3 is a circuit diagram showing a partial insulating layer. The partial insulating layer has a first track or "linking track" 301 that connects HTS cables 311, 312 on either side of the partial insulating layer (equivalent to Figure 2D The partially insulated layer also has a second track or "pickup track" 302 that is electrically insulated from the HTS cables 311, 312 and inductively coupled to the first track (represented by transformer 303). The second track 302 is connected to a current monitor 304. Note that while the resistor and transformer are Figure 3 , but in the example below, the resistive and inductive coupling are due to the length and shape of the track itself - i.e., the resistor and transformer do not need to be provided as separate components.

[0051] Due to the inductive coupling between the first and second rails, any change in the current of the first rail (e.g. due to a quench) will result in a corresponding change in the current of the second rail. This can then be detected by the current monitor, and the measurement from the current monitor can be used by the controller of the magnet to detect a quench.

[0052] Various changes may be used to increase the sensitivity of quench detection. For example, the linking track and the pickup track may be shaped to provide greater inductive coupling, such as as coils sharing a common axis. Multiple pickup tracks may be provided (each corresponding to a separate linking track) and the multiple pickup tracks connected in parallel to each other and to the current monitor so that the current monitor measures the total current induced in all the pickup tracks.

[0053] Figures 4A to 4F Shows the implementation Figure 3 An exemplary partial insulating layer of a circuit. The partial insulating layer includes 11 layers, 6 of which contain conductive elements, and each layer is separated by an insulating layer 401 (the insulating layer 401 can be an insulator with a conductive layer printed thereon, such as kapton™ tape, or an insulating adhesive). The layers containing conductive elements are, in order:

[0054] • A first metal connection layer 410, such as Figure 4B shown.

[0055] • Link track layer 420, e.g. Figure 4C shown.

[0056] • Pick up track layer 430, e.g. Figure 4D shown.

[0057] • Pick up track connection layer 435, e.g. Figure 4E shown.

[0058] • A second metal connection layer 440, such as Figure 4F shown.

[0059] Figure 4A is along Figures 4B to 4F The cross section of line AA in .

[0060] The first metallic connection layer 410 and the second metallic connection layer 440 are substantially the same as those used in the previous examples - that is, the first metallic connection layer and the second metallic connection layer are placed in place to facilitate electrical connection to the HTS cable.

[0061] The link track layer includes a plurality of link tracks 421, which in this example are formed as a spiral 422 having a tail 423. The center of the spiral 422 is connected to a conductive link 402, which extends through the insulating layer to connect the link track 421 to the first metal connection layer, and the other end of the tail 423 is connected to a conductive link 403, which connects the link track 421 to the second metal connection layer. As in the previous example, the conductive link can be formed as a hole coated with metal.

[0062] The pickup track layer 430 contains a pickup track 431 corresponding to each link track 421. Each pickup track is a spiral of the same size as the corresponding link track 421 and is located directly below the link track 421. Each pickup track is connected to the routing track 432 at the outside of the spiral through a conductive link 404 (which connects the inside of the spiral to the track 436 in the pickup track connection layer 435) and a conductive link 405 (which connects the track 436 to the routing track 433), and is connected to the routing track 433 via the inside of the spiral.

[0063] The connection of the pick-up track 431 to the routing tracks 432, 433 ensures that the pick-up track 431 is connected in parallel. This means that when the routing tracks 432, 433 are connected via an ammeter (not shown, but the routing track has a disc 434 extending to the edge of the layer to allow connection to routing tracks of other sections of the partially insulating layer or to an ammeter), the current measured by the ammeter will be the sum of the currents in the pick-up track.

[0064] The conductive link 403 between the link track layer and the second metal connection layer also passes through the pickup track layer and the pickup track connection layer, but the conductive link 403 is not electrically connected to other elements in those layers.

[0065] To avoid interference, the link track and pickup track should be arranged so that they do not significantly couple to the magnetic field of the magnet, e.g. the cross section perpendicular to the local magnetic field is negligible. This can be achieved by placing the link track and pickup track in the plane of the partial insulating layer, as shown in the example above, but other orientations are possible.

[0066] Figure 5 An alternative arrangement of link tracks is shown (which may also be applied to pick-up tracks). Instead of providing Figure 4C The curved spiral coil in the link track layer 520 (which can be replaced by the design of the link track layer 420) is a square coil 522.

[0067] Fig. 6A and 6B Another alternative arrangement of link tracks is shown. Figure 4A The link track layer 420 is replaced by a first link track layer 620 and a second link track layer 625. The link tracks are formed into a "butterfly coil" in an "8-shaped" pattern. Since this pattern contains areas where the tracks will cross each other, they should be arranged in two layers to avoid short circuits - Fig. 6A and 6BOne such arrangement is shown in , with the main portion of the butterfly coil 622 provided on layer 620 and the cross track 626 provided on a separate layer 625, with a conductive link 627 between the cross track and the main portion of the butterfly coil. Other arrangements to avoid short circuits are possible and can be readily envisioned by the skilled person.

[0068] Figures 4A to 6B The coil designs in are by way of example only. Any arrangement that causes the pickup track to be sensitive to current changes in the link track (ie, indicatively coupled to the link track) can be used to detect current leakage through part of the insulation layer.

[0069] Fig. 7A and 7B An alternative design is shown in . Fig. 7A and 7B A portion of the insulating layer 701 is shown, comprising:

[0070] ·The first metal connection layer (with Figures 2A to 2E The same as layer 211 in FIG. 1 );

[0071] Link track layers (with Figures 2A to 2E same as layer 230 in );

[0072] Pick up track layer 710; and

[0073] · The second metal connection layer (with Figures 2A to 2E same as layer 212 in FIG. 1 ).

[0074] As in the previous example, these layers are separated by an insulating layer 701 .

[0075] The pick-up track layer 710 includes a pick-up track 711 that extends along the coil so as to couple with the spiral path of the HTS magnet and an inductive link 712 that connects the link track layer to an external interface layer (not connected to the pick-up track). The pick-up track 711 has connection pads on each end that are then connected to a voltmeter. The pick-up track 711 is in close proximity to the coil conductor and will be inductively coupled with the coil conductor. The voltage that appears on the coil will also appear on the co-wound track and will be detected by the voltmeter. Other connection pads can be provided along the length of the partial insulating layer, allowing the connection pads to be easily mass-produced and then cut to a certain length as required by the magnet (i.e., ensuring that the connection pads can be available at the ends of the partial insulating layer regardless of the size of the HTS coil).

[0076] The above-mentioned partial insulating layers can be made using a flexible PCB manufacturing process, i.e., starting from one of the insulating layers, applying copper to its upper and lower surfaces, and etching the copper to form two adjacent conductive layers. More layers can be added by applying more insulating layers and copper layers to the stack (wherein the insulating layer can be an adhesive for bonding the next copper layer to the stack) and then etching, or by bonding more "copper-coating and etched insulating layers" together (for example, to form a "copper-insulator-copper-adhesive-copper-insulator-copper" structure). Vias can be formed by drilling through appropriate copper and insulating layers, and then the vias are coated with copper to provide connectors between copper layers (i.e., the conductive links of the above examples). If the via passes through a layer that should not be electrically connected to it, the area around the via of the layer can be etched to ensure a clear insulating space between the via and the conductive components of the layer. When this occurs on an outer layer (e.g., metal connection layer 410, 440), an insulating cap can be fixed to the end of the via to prevent short circuits due to welding or connection to the HTS cable.

[0077] Although reference is made above to a single 'partially insulating layer' of the coil, it will be appreciated that this could consist of several sections connected end to end, or with connections between the pick-up track layers, or with separate current sensors for each section of the pick-up track layers (or some combination - e.g. a current sensor for every N sections).

[0078] The partial insulation layer may have the same width as the HTS tape. The method of winding the HTS flat coil may involve pulling the HTS tape from multiple spools to form a "cable" of many tapes that are gathered at the coil. The partial insulation layer will be fed along with the multi-tape cable to form the wound section. The final coil structure will be a multi-tape cable interwoven with the partial insulation layer. The tape and the outer surface of the partial insulation layer are pre-wetted with a fluid and then immersed in solder to consolidate the winding package. The coil surface is then cleaned to ensure that solder bridges do not bypass the partial insulation layer from turn to turn.

[0079] Once wound and consolidated, the ends of the partial insulation layers on the outer diameter of the coil are slightly stripped back so that a pair of fine wires can be attached to the contact pad at the end of the pickup coil layer. This twisted pair of wires is connected to a current transducer that is used to detect a signal of current flowing in the leaking insulation.

[0080] It will be appreciated that the above examples (i.e., providing a pickup track that is inductively coupled to the HTS coil or a resistive path through a partial insulating layer) may be modified in a simple manner without departing from the principles of the present disclosure. For example, the connection layer on the outer surface of the partial insulating layer may be omitted, and the connection between the connection track layer and the HTS cable may be made directly through a conductive link, or the partial insulating layer may have a connection track and a pickup track disposed within a solid insulator, rather than the multi-layer structure described above.

Claims

1. A high temperature superconducting field coil, comprising one or more high temperature superconducting cables and one or more partial insulation layers, wherein: The one or more high temperature superconducting cables are arranged to form turns, and the one or more partial insulation layers are arranged to radially connect the turns, and wherein the partial insulation layers comprise: An insulator having within the insulator: a set of linking tracks, wherein each linking track is electrically conductive and electrically connected to the first and second surfaces of the portion of the insulating layer to provide an electrical path between the first and second surfaces; and a set of pickup tracks, wherein each pickup track is electrically conductive and inductively coupled to a corresponding link track and is electrically insulated from the first and second surfaces; Therein, each pickup track is configured to be connected to a current measuring device in order to measure a current induced in said pickup track due to a change in the current flowing in the corresponding link track.

2. The high temperature superconducting field coil according to claim 1, wherein: The set of pickup tracks are connected in parallel and are configured to be connected in parallel to the current measuring device.

3. The high temperature superconducting field coil according to claim 2, wherein: The pickup tracks are arranged such that when the partial insulating layers are connected end-to-end to the same other partial insulating layer, the pickup tracks on both partial insulating layers are connected in parallel to each other and to the current measuring device.

4. The high temperature superconducting field coil according to claim 1, wherein: Each pickup track and each link track has a spiral section.

5. The high temperature superconducting field coil according to claim 1, wherein: Each pickup track and each link track has a section that is a butterfly coil.

6. The high temperature superconducting field coil according to claim 1, wherein: Each linking track is electrically connected to the first and second surfaces through a via coated with an electrical conductor.

7. A high temperature superconducting field coil, comprising one or more high temperature superconducting cables and one or more partial insulation layers, wherein: The one or more high temperature superconducting cables are arranged to form turns, and the one or more partial insulation layers are arranged to radially connect the turns, and wherein the partial insulation layers comprise: An insulator having within the insulator: a set of linking tracks, wherein each linking track is electrically conductive and electrically connected to the first and second surfaces of the portion of the insulating layer to provide an electrical path between the first and second surfaces; and a pickup track, wherein the pickup track is electrically conductive, extends along a length of the portion of the insulating layer, and is electrically insulated from the first and second surfaces; Therein, the pickup track is configured to be connected to a voltage measuring device in order to measure a voltage induced in the pickup track due to a change in current in the high temperature superconducting conductor of the high temperature superconducting field coil.

8. The high temperature superconducting field coil according to claim 7, wherein: The pickup tracks are arranged such that when the partial insulating layers are connected end-to-end to the same other partial insulating layer, the pickup tracks on the two partial insulating layers are connected in series with each other and with the voltage measuring device.

9. The high temperature superconducting field coil according to claim 1 or 7, wherein: The partial insulating layer is formed into a plurality of layers, each of which is separated by an insulating material, and the layers include: a link track layer, wherein the link track layer has the link track; and A pickup track layer, wherein the pickup track layer has the pickup track; The electrical connection between the link track and the first surface and the second surface is achieved through vias penetrating the insulating material, and the vias contain conductive material.

10. The high temperature superconducting field coil according to claim 1 or 7, comprising: A conductive connection layer is electrically connected to the linking tracks on each of the first and second surfaces.

11. The high temperature superconducting field coil according to claim 1 or 7, wherein: The one or more high temperature superconducting cables and the one or more partial insulation layers are continuously wound to form the turns.

12. The high temperature superconducting field coil according to claim 1 or 7, wherein: The one or more high temperature superconducting cables and the one or more partial insulation layers are arranged in a plurality of sections connected by joints.

13. A tokamak comprising a toroidal field coil, wherein the toroidal field coil is a high temperature superconducting field coil according to claim 1 or 7.

14. A proton beam therapy device, comprising the high temperature superconducting field coil according to claim 1 or 7, wherein: The high temperature superconducting field coil is one of the following: Field coils of an accelerator of the proton beam therapy device; A dipole or quadrupole magnet of a proton beam guidance system of the proton beam therapy device.

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