High temperature superconducting coil with resistively impregnated windings and method for manufacturing same

Abstract

The invention relates to a high-temperature superconducting coil HTSC, comprising a tape HTS-TP made of high-temperature superconducting material wound in a number of turns, and a resistive layer RL arranged between and in contact with the windings, characterized in that the resistive layer RL comprises a mesh MSH made of a metal-based material having a first electrical resistivity and an impregnation material IM having a second electrical resistivity different from the first electrical resistivity and filling the mesh, or a tape TP made of a metal-based material having a first electrical resistivity and patterned with through openings TO, and an impregnation material IM having a second electrical resistivity different from the first electrical resistivity and filling the through openings.

Description

[Technical Field]

[0001] The present invention relates to the field of superconducting magnets, and more particularly to high temperature superconducting magnets. [Background technology]

[0002] An important aspect to consider with respect to superconducting magnets is the irreversible change of state from the superconducting state to the resistive state, known as a “quench.” Superconducting magnets need to be protected from this phenomenon, as it can cause irreversible damage, particularly due to thermal heating induced by the propagation of resistive regions inside the superconducting magnet.

[0003] This is a well-known problem with all superconducting magnets, but becomes crucial when considering high temperature superconductors (HTS).

[0004] Indeed, during a quench of an HTS magnet, the propagation velocity of the resistive region (i.e., the non-superconducting "normal" region) is very slow and the associated resistive voltage consequently increases very slowly, which generally results in delayed voltage detection of the quench and a high risk of thermally induced local damage to the HTS magnet.

[0005] Solutions to avoid this situation have already been proposed, especially for HTS coils.

[0006] One way to protect HTS coils in the event of localized resistive transients is to remove all electrical insulation between the windings. This allows current to automatically bypass resistive areas of the HTS coil by redirecting the current path from one winding to another (radially). This is a proven and effective method of protection against thermal damage. However, the main drawback of such a solution is the large electrical time constant of radial currents, especially during magnet charging. Another drawback is that the windings are not mechanically coupled together (this approach is also referred to in the literature as the "dry winding technique"). Both drawbacks lead to complex mechanical behavior (some windings of the coil lose contact with each other, limiting the self-protection behavior), heat dissipation, and loss of magnetic field quality when the coil is charged or discharged. Furthermore, the "dry winding technique" is not optimal for internal cooling of the coil due to "voids" inside the windings caused by variations in the thickness and width of the superconducting cable.

[0007] An alternative solution is based on the "Metal-as-Insulation Technology" (MI), which essentially consists of adding a resistive layer made of metal tape between the windings of an HTS coil. The metal tape adds resistance not only due to its own material but also due to its contact with the coil windings. This reduces current bypass under normal operating conditions and at the same time reduces the associated electrical time constant. This solution therefore dramatically reduces current bypass between the windings and also limits unwanted unbalanced forces and torques between elements inside the coil. The resistance can be set by the choice of metal for the tape and its thickness. The effectiveness of this solution for high magnetic fields has been proven in recent studies, see for example the paper in Non-Patent Document 1 (A1).

[0008] Certain designs have also been proposed to make it easier to set the resistance value of the metal tape.

[0009] For example, in the field of PI technology, Patent Document 1 (A2) proposes a partial insulation structure made of a metal tape sandwiched between two insulating layers, each of which has a window that allows electrical contact with the windings of the HTS coil, and which is further offset from one insulating layer to the other. The number of windows for each insulating layer and the offset of the windows from one insulating layer to another can set the resistance of the partial insulation layer. This document also proposes a solution to ensure that the tape is mechanically connected to the HTS coil, for example, by adhesive (e.g., epoxy resin) or mechanical means. In such a method, the disadvantages of the "dry winding technique" are no longer encountered.

[0010] As another example, more recently, an alternative solution to MI technology has been proposed. It is based on using a resistive layer made of an electrically charged conductive epoxy resin between the windings of the coil. Reference can be made to Non-Patent Document 2 (A3). This solution provides a resistance between the windings of the coil, similar to that provided by MI technology. The resistance value can be set during manufacturing by adjusting the different components of the epoxy solution. Furthermore, as already mentioned, the epoxy solution (resin) forms an adhesive once it dries, which allows for a mechanical connection with the windings of the HTS coil.

[0011] A recent review of existing techniques is given in the article [3] (A4). [Prior art documents] [Patent documents]

[0012] [Patent Document 1] International Publication No. 2019 / 150123 [Non-patent literature]

[0013] [Non-Patent Document 1] Ph. Fazilleau et al, "38 mm cold bore metal-as-insulation HTS insert reached 32.5T in a background magnetic field generated by resistive magnet", Cryogenics, Volume 106 (2020) [Non-patent document 2] Bouloukakis & al., "Discharge Behavior and Modeling of a 1.5 T REBCO Magnet With Quench Tolerant Coils Impregnated With Conductive Epoxy," in IEEE Transactions on Applied Superconductivity, vol. 31, no. 5, pp. 1-5, Aug. 2021, Art no. 4601105, doi: 10.1109 / TASC.2021.3059975 [Non-patent document 3] T. Lecrevisse et al, Supercond. Sci. Technol., 35 (2022), 074004 (pp.18) Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is to propose an alternative solution. [Means for solving the problem]

[0015] To achieve the object, the present invention provides a high-temperature superconducting coil, a tape made of high-temperature superconducting material wound in multiple windings; a resistive layer disposed between and in contact with said windings, characterized in that it comprises a mesh made of a metal-based material having a first electrical resistivity and an impregnating material, either dielectric or conductive, having a second electrical resistivity different from the first electrical resistivity, filling said mesh, or a tape made of a metal-based material having a first electrical resistivity, patterned with through openings, and an impregnating material, either dielectric or conductive, having a second electrical resistivity different from the first electrical resistivity, filling said through openings; A high-temperature superconducting coil is proposed.

[0016] Other features of the coil according to the invention, taken alone or in combination, are provided as follows: The mesh is a fabric, such as a woven or knitted fabric. The tape having the through-openings patterned thereon is made of a zigzag tape. The metal-based material for the mesh or for the tape patterned with through-openings is selected from the group consisting of stainless steel or non-stainless steel, copper or copper alloy, aluminum or aluminum alloy. The impregnating material is either a dielectric material selected from the group consisting of resins such as epoxy resins, waxes, oxide pastes, or metal-based materials. the mesh or the tape patterned with through-openings is covered with a coating for adjusting the contact resistance between the mesh or the tape patterned with through-openings on the one hand and a tape made of high-temperature superconducting material on the other hand. the second electrical resistivity of the impregnating material is different from the first electrical resistivity of the metal-based material from which the mesh or tape patterned with through-openings is made.

[0017] The present invention also provides a method for manufacturing a high-temperature superconducting coil according to the present invention, comprising the steps of: a) the following sub-steps: a1) providing a tape made of a high temperature superconducting material; a2) providing a tape patterned with a mesh or through openings made of a metal-based material having a first electrical resistivity; a3) placing the mesh (MSH) or the tape patterned with through-openings on a tape made of high temperature superconducting material; a4) impregnating the mesh or the tape patterned with through-openings with an impregnation material having a second electrical resistivity different from the first electrical resistivity of the metal-based material of the mesh or tape; Building a laminate by the mesh or the tape patterned with through-openings is intended to form the resistive layer together with an impregnating material; Steps and b) winding the laminate onto itself to create a winding; c) curing the impregnating material of the laminate; The present invention proposes a method including:

[0018] Other features of the method according to the invention, taken alone or in combination, are provided as follows: Sub-steps a3) and a4) are carried out simultaneously. Step b) is carried out simultaneously with sub-step a4). Step b) is carried out between sub-step a3) and sub-step a4).

[0019] Other features and advantages of the present invention will become apparent from the following detailed description, which is based on the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a diagram of a high temperature superconducting coil according to the present invention. [Figure 2] 1 is a cross-sectional view of a high temperature superconducting coil according to the present invention, taken between two windings of said coil. [Figure 3] FIG. 10 is a top view of a mesh that can be used in the resistive layer of the coil. [Figure 4(a)] FIG. 1 is a perspective view of an alternative in which the mesh is replaced with tape with through-openings according to the first embodiment. [Figure 4(b)] FIG. 10 is a perspective view of an alternative in accordance with a second embodiment in which the mesh is replaced by tape with through-openings. [Figure 4(c)] FIG. 10 is a top view of an alternative in accordance with a third embodiment, where the mesh is replaced with tape having through-openings. [Figure 5] FIG. 10 is a cut-through view through the thickness of another alternative in which the mesh is covered with a coating to further adjust the contact resistance with the high temperature superconducting tape. [Figure 6] 1 is an overview of the various steps of a possible method for manufacturing a high temperature superconducting coil according to the present invention. [Figure 7] 1 shows an outline of the experimental setup for testing high-temperature superconducting coils. [Figure 8] 8 is a curve showing the variation of the central magnetic induction (mT) in the coil after a 20 A discharge versus time (ms) for several tests obtained with the experimental setup of FIG. 7. [Figure 9] 8 is a curve showing the variation of the coil current (A), voltage (V), and central magnetic induction (mT) over time (s) obtained with the experimental setup of FIG. 7 to confirm the stability of the coil with respect to quenching. [Figure 10] 8 is a curve showing the change in current (A), voltage (V), and central magnetic induction (mT) of the coil over time (s) obtained with the experimental setup of FIG. 7 to confirm the robustness of the coil against pulsed quenches. DETAILED DESCRIPTION OF THE INVENTION

[0021] A high temperature superconducting coil HTSC according to the present invention is shown in FIG. 1 (overall view) and FIG. 2 (cutaway view).

[0022] The high-temperature superconducting coil HTSC comprises a tape HTS-TP wound in several turns and made of high-temperature superconducting material, and a resistive layer RL arranged between and in contact with said turns. In Figure 2 it can be seen that the resistive layer is shown between two consecutive turns of the tape HTS-TP.

[0023] The resistive layer RL can be fabricated in a variety of ways.

[0024] In FIG. 3, the resistive layer RL comprises a mesh MSH made of a metal-based material having a first electrical resistivity and an impregnation material IM having a second electrical resistivity different from the first electrical resistivity and filling the mesh MSH.

[0025] The mesh MSH may in particular be a fabric, such as a woven or knitted fabric, for example a stainless steel woven fabric (thin fabric) may be used.

[0026] In FIG. 4, the resistive layer RL comprises a tape TP made of a metal-based material having a first electrical resistivity and having through openings TO patterned therein, and an impregnating material IM having a second electrical resistivity different from the first electrical resistivity and filling the through openings.

[0027] More precisely, FIG. 4(a) shows a tape in which the through apertures are all holes of the same size (given dimensions), and more preferably evenly distributed along the tape.

[0028] FIG. 4(b) shows a tape in which the through openings are holes with variable dimensions and ultimately are not evenly distributed along the tape.

[0029] FIG. 4(c) shows a tape in which the through openings are obtained by the zigzag shape of the tape.

[0030] In either case, the metal-based material for the mesh MSH or for the tape TP patterned with through openings TO can be selected from steel, stainless steel, copper and copper alloys (including copper beryllium alloys, brass, etc.), aluminum and aluminum alloys.

[0031] In addition, in both cases, the impregnating material IM can be either a resin such as an epoxy resin, a wax, a dielectric material selected from oxide pastes, or a metal-based material, with resins being particularly well suited due to their bonding properties and their high dielectric properties.

[0032] The mesh MSH or the tape TP patterned with said through openings TO can be covered with a coating CTG, which may be useful for adjusting the contact resistance between said mesh MSH or the tape TP patterned with said through openings TO on the one hand and the tape HTS-TP made of high-temperature superconducting material on the other hand.

[0033] For example, FIG. 5 shows the deposition of a mesh inside the resistive layer when used.

[0034] Of course, the coating can also be deposited on the surface of the tape TP with through openings TO that is intended to be in contact with the high-temperature superconducting tape HTS-TP for any of the alternatives represented in Figures 4(a) to 4(d) (not shown).

[0035] The coating can be deposited by atomic layer deposition (ALD) with a thickness typically comprised between 100 nm and 1 μm. The coating can be made of, for example, aluminum oxide or a mixture of aluminum oxide and zinc oxide.

[0036] FIG. 6 shows a possible method for manufacturing a high temperature superconducting coil HTSC according to the invention.

[0037] The first step 100 comprises the following sub-steps: a sub-step 101 of providing a tape HTS-TP made of high-temperature superconducting material; a substep 102 of providing a mesh MSH or a tape TP patterned with through openings TO, made of a metal-based material having a first electrical resistivity; substep 103 of placing said mesh MSH or said tape TP patterned with through-openings TO on a tape made of high-temperature superconducting material; a substep 104 of impregnating said mesh MSH or said tape TP patterned with said through openings TO with an impregnation material IM having a second electrical resistivity different from said first electrical resistivity of the metal-based material of said mesh MSH or tape TP; The purpose of the present invention is to build a laminate by

[0038] The mesh MSH or the tape TP patterned with said through openings TO is intended to form, together with the impregnation material IM, a resistive layer RL.

[0039] The second step 200 consists in winding the laminate onto itself to create the winding.

[0040] The third step 300 consists in curing the impregnating material IM of said laminate.

[0041] The method of manufacture can be carried out in successive steps and in the order set forth herein, but this is not required.

[0042] For example, sub-steps 103 and 104 can be performed simultaneously.

[0043] As another example, step 200 can be performed simultaneously with sub-step 104 .

[0044] As another example, step 200 can be performed between sub-steps 103 and 104.

[0045] Proof of concept A high temperature superconducting coil was fabricated as described above.

[0046] The high temperature superconducting tape ("HTS tape") selected is 6 mm wide and 76 μm thick, requiring a total of 25.5 m to wind the pancake coil.

[0047] The resistive layer is made of a stainless steel mesh filled with epoxy resin as an impregnation material. The mesh is more precisely a woven fabric (thin fabric). The thin fabric is considered to have 30 μm strands for a total thickness of 60 μm. The open area (%) of this mesh, through which the epoxy resin can pass, is 49%. The length and width of the mesh correspond to those of the HTS tape. A room-temperature curing epoxy resin with a thermal contraction coefficient similar to that of the HTS material was used for the proof-of-concept pancake coil.

[0048] The winding and impregnation of the superconducting tape together with the mesh was carried out simultaneously.

[0049] The pancake coil has approximately 100 turns and exhibits an inner diameter of 60 mm and an outer diameter of 99.1 mm. The coil inductance is 1.035 mH and the coil magnetic constant is 1.617 mT / A.

[0050] Experimental equipment and results To demonstrate the self-protective behavior of the coil detailed in the "Proof of Concept" section, an experimental setup was used to test its behavior.

[0051] For this purpose, the coil HTSC was immersed in a liquid nitrogen (LN2) bath BTH at 77 K. The voltage U and current I of the coil were monitored (this can be done by adding two soldered taps to both ends of the coil) and the central magnetic induction of the coil was monitored using a Hall sensor (Arepoc).

[0052] An outline of the experimental setup is shown in Figure 7 (Hall sensors not shown).

[0053] Approximately 60 tests were carried out using this coil, including three thermal cycles from room temperature to LN2 bath conditions (77 K) and many quench tests.

[0054] FIG. 8 shows the variation of central magnetic induction (mT) versus time (s) for a sudden discharge of 20 A current for 16 of the 60 tests performed.

[0055] First, the coil HTSC is charged by the power supply PS in a ramp up to 20 A, for which the mechanical contactor MC is closed. Next, the mechanical contactor MC is suddenly opened. Finally, the magnetic field is monitored against the time from the opening of the mechanical contactor MC (t=0 s).

[0056] This type of test allows evaluation of the contact resistance between the high temperature superconducting tape and the resistive layer.

[0057] It can be seen that the curves are similar for all tests represented in Figure 7, meaning that the contact resistance is constant. Therefore, a reproducible behavior of the coil during charging and discharging can be expected, even after thermal cycling and quenching. It also indirectly indicates that the contact between the HTS tape and the resistive layer (mesh + epoxy resin) is maintained. In fact, the epoxy resin bonds the resistive layer between the two windings of the HTS tape.

[0058] FIG. 9 shows the variation of the coil current I (A), voltage U (V) and central magnetic induction B (mT) over time (s) in the first test situation.

[0059] First, the coil is charged with 2 A below the quench current (a ramp from 0 to 20 s; current 70 A). Next, to passively protect the coil, the power supply voltage is kept constant at a low value for approximately 60 s (from 20 to 78 s), and the strength is kept constant at 70 A for the same time period. The current is then increased stepwise by 1 A until quenching (from 88 to 92 s; quench at 72 A). At t=92 s, a discharge can be observed: the current dramatically and suddenly decreases to a value of 32 A, indicating the coil's self-protection against quenching. Simultaneously with the current decrease, the voltage rises to 0.7 V (the limit imposed by the power supply). At t=145 s, the current decreases ramp-like and gradually cuts off. It should be noted that the changes in the central magnetic induction with the current are similar and, due to the scale chosen in Figure 9, are superimposed. Therefore, in Figure 9, only two curves can be practically distinguished.

[0060] FIG. 10 shows the variation of the coil current I (A), voltage U (V), and central magnetic induction (mT) over time (s) in another test situation.

[0061] First, the coil is charged to 134 A at a ramp rate of 200 A / s (pulse current test). This current value corresponds to approximately 1.86 times the quench current (72 A as mentioned above). A discharge can then be observed immediately, with the current dramatically and suddenly decreasing to 32 A, indicating the coil's self-protection against quenching. The current pulse is unable to heat a sufficient volume of the coil to maintain it in the altered state, so the voltage also decreases at the same time (unlike the test shown in Figure 9). At t = 17 s, the coil, frozen by the cryogenic bath, becomes superconducting again. Finally, at t = 34 s, a new current pulse is sent, and the behavior is identical. It should be noted that the changes in the central magnetic induction with the current change are similar and, due to the scale chosen in Figure 10, are superimposed on top of each other. Therefore, in Figure 10, only two curves can be distinguished.

Claims

1. A high temperature superconducting coil (HTSC), a tape made of high temperature superconducting material (HTS-TP) wound as multiple windings; a resistive layer (RL) disposed between and in contact with the windings, a mesh (MSH) made of a metal-based material having a first electrical resistivity, and an impregnating material (IM) filling said mesh, said impregnating material being either dielectric or conductive but having a second electrical resistivity different from said first electrical resistivity; or a tape (TP) made of a metal-based material having a first electrical resistivity and patterned with through openings (TO), and an impregnating material (IM) that is dielectric or conductive but has a second electrical resistivity different from said first electrical resistivity and fills said through openings; a resistive layer (RL), A high-temperature superconducting coil comprising:

2. 2. A high temperature superconducting coil (HTSC) according to claim 1, characterized in that the mesh (MSH) is a fabric such as a woven or knitted fabric.

3. 3. A high temperature superconducting coil (HTSC) according to claim 1 or 2, characterized in that the tape (TP) on which the through openings (TO) are patterned is made of a zigzag tape.

4. 4. A high temperature superconducting coil (HTSC) according to any one of claims 1 to 3, characterized in that the metal-based material for the mesh (MSH) or for the tape (TP) with patterned through openings (TO) is selected from the group consisting of stainless steel or non-stainless steel, copper or copper alloy, aluminum or aluminum alloy.

5. 5. A high temperature superconducting coil (HTSC) according to any one of claims 1 to 4, characterized in that the impregnation material (IM) is a dielectric selected from the group consisting of a resin such as an epoxy resin, a wax, an oxide paste, or a metal-based material.

6. 6. A high-temperature superconducting coil according to any one of claims 1 to 5, characterized in that the mesh (MSH) or the tape (TP) patterned with the through openings (TO) is covered with a coating (CTG) for adjusting the contact resistance between the mesh (MSH) or the tape (TP) patterned with the through openings (TO) on the one hand and the tape (HTS-TP) made of high-temperature superconducting material on the other hand.

7. 7. A high temperature superconducting coil (HTSC) according to any one of claims 1 to 6, characterized in that the second electrical resistivity of the impregnating material is different from the first electrical resistivity of the metal-based material from which the mesh (MSH) or the tape (TP) with patterned through openings (TO) is made.

8. A method for manufacturing a high temperature superconducting coil (HTSC) according to any one of claims 1 to 7, comprising: a) the following sub-steps: a １ 2.) providing a tape (HTS-TP) made of high temperature superconducting material; a ２ a) providing a mesh (MSH) or a tape (TP) patterned with through-holes (TO) made of a metal-based material having a first electrical resistivity; a ３ ) placing the mesh (MSH) or a tape (TP) patterned with the through-openings (TO) on top of the tape made of high-temperature superconducting material; a ４ ) impregnating the mesh (MSH) or the tape (TP) patterned with the through openings (TO) with an impregnation material (IM) having a second electrical resistivity different from the first electrical resistivity of the metal-based material of the mesh (MSH) or the tape (TP); Building a laminate by the mesh (MSH) or the tape (TP) patterned with the through openings (TO) is intended to form the resistive layer (RL) together with the impregnating material (IM); Steps and b) winding the laminate on itself to create a winding; c) curing the impregnating material (IM) of the laminate; A method comprising:

9. The sub-step a ３ ) and the sub-step a ４ 9. The method according to claim 1, wherein the steps of:

10. Step b) is performed by the sub-step a ４ 9. The method of claim 8 , wherein the step of

11. Step b) is performed by the sub-step a ３ ) and the sub-step a ４ 9. The method of claim 8, wherein the step of

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