A critical performance testing device and method for superconducting wires in high background fields

Abstract

This invention discloses a sample rod and device for critical performance testing of high-current, multi-channel switchable superconducting wires in high background fields. The current lead is divided into three sections: the bottom section is a high-temperature superconducting current lead, and the middle section can be disassembled, replaced, or have its current increased or decreased according to the performance and quantity of the test samples. The test sample plate has radially extending limiting grooves to accommodate multiple samples, making excellent use of the limited space of the cylindrical Dewar. Simultaneously, the power switch can switch the current lead in a high-field environment without lowering the field, thus achieving the purpose of testing different samples.

Description

Technical Field

[0001] This invention relates to the field of critical performance testing of superconducting wires, and more particularly to a device and method for testing the critical performance of superconducting wires in a high background field. Background Technology

[0002] A steady-state strong magnetic field, like extremely low temperatures and ultra-high pressures, is an extreme experimental condition required for studying matter. Under strong magnetic field conditions, the properties of matter can be modulated, allowing scientists to discover new phenomena and explore new laws governing matter. Currently, most devices generating steady-state strong magnetic fields are water-cooled magnets, especially those exceeding 20T. Water-cooled magnets are primarily composed of stacked copper-silver alloy plates. When an electric current is applied, a magnetic field is generated at the center of the plates. However, the resistance of the copper-silver alloy is not negligible, meaning that the plates generate a large amount of Joule heat when current is applied. Therefore, deionized water is continuously supplied to water-cooled magnets during operation to dissipate the heat generated by the plates. This not only consumes a large amount of electricity, but the cooling of the deionized water also takes time, meaning that water-cooled magnets are difficult to operate continuously.

[0003] Compared to water-cooled magnetic fields, superconducting magnets offer higher magnetic fields, smaller size, and can operate continuously under low-temperature conditions. These advantages make superconducting magnets the mainstream material for future high magnetic field development. Superconducting magnets are primarily made by winding superconducting wires / tapes. Currently, most common superconducting magnets are made from low-temperature superconducting materials such as NbTi or Nb3Sn. However, low-temperature superconducting materials are limited by their upper critical field, making them only suitable for superconducting magnets with a field strength below 23T. To create superconducting magnets with higher field strengths, high-temperature superconducting materials with even higher upper critical fields must be used, such as Bi-2212, Bi-2223, and YBCO. Currently, the fabrication of superconducting magnets using high-temperature superconducting materials is still in the laboratory stage, and the current-carrying capacity and mechanical strength of superconducting wires / tapes are continuously being optimized. Taking Bi-2212 superconducting material as an example, Bi-2212 exhibits excellent current-carrying capacity under high fields, maintaining a critical current of over 400A even in a 20T background magnetic field. The high current-carrying capacity of superconducting wires necessitates high current-carrying capacity in the current leads. Currently, most current leads are made of oxygen-free copper, and high current-carrying capacity means that the oxygen-free copper is larger in volume. However, the background magnets exceeding 20T widely used in experimental testing are water-cooled magnets. During experiments, a Dewar containing the test sample is inserted into the center of the water-cooled magnet, and the temperature is lowered by introducing liquid helium into the Dewar. Limited by the room-temperature aperture of the water-cooled magnet, the space of the Dewar containing the sample is also relatively small. This smaller space means that the number of samples that can be loaded is limited, and the large volume of oxygen-free copper current leads also occupies most of the Dewar's space. Therefore, for experiments with a large number of samples, repeated sample replacements are necessary, resulting in significant liquid helium consumption. Furthermore, during high background magnetic field experiments, the high magnetic field can be harmful to the human body. How to change the current leads to test different samples within a single test also presents a problem. The most common practice is to first reduce the background magnetic field strength to 0T, then manually replace the current leads, and then increase the background magnetic field strength again. This practice lengthens the testing time and negatively impacts the operating time of the water-cooled magnet and the consumption of liquid helium. Summary of the Invention

[0004] The technical problem to be solved by this invention is how to save liquid helium during experiments and how to optimize the testing process by switching the power switch under high field conditions.

[0005] The present invention solves the above-mentioned technical problems through the following technical means: A critical performance testing device for superconducting wires in high background fields includes a test rod, which comprises a sealing flange, an aviation plug, a liquid helium return port, a liquid helium inlet, and a room temperature terminal block mounted on one side of the sealing flange; a hanging rod is fixed on the other side of the sealing flange; multiple support plates are spaced apart on the hanging rod; multiple through holes are opened on the support plates, the top end of a current lead is connected to the room temperature terminal block, and the bottom end passes through multiple support plates and is detachably connected to a high-temperature superconducting current lead; the current lead is a binary current lead, the upper part is made of oxygen-free copper braided wire, and the lower part... Made of YBCO high-temperature superconducting material; the upper current lead includes a first current lead in the upper half and a second current lead in the lower half; the first current lead and the second current lead are detachably connected, the diameter of the first current lead is larger than that of the second current lead, and the second current lead can be easily removed from the sample rod. It can be added, removed, or replaced according to the number and performance of the samples, greatly saving liquid helium; multiple limiting grooves are radially opened from the center of the test sample plate, and electrodes are fixed at the ends of the multiple limiting grooves away from the center of the test sample plate, with multiple high-temperature superconducting current leads connected to the corresponding electrodes. The power switch switching device is simple and easy to manufacture, allowing switching of current leads under high background fields, avoiding the labor and time consumption caused by changing current leads under reduced background fields, while also saving liquid helium to a certain extent.

[0006] Furthermore, a through slot is provided perpendicular to the direction of the limiting slot for the voltage signal line to pass through; the depth of the through slot is greater than that of the limiting slot.

[0007] Furthermore, the high-temperature superconducting current lead is an oxygen-free copper busbar with grooves; YBCO high-temperature superconducting tape is welded in the grooves, and the oxygen-free copper busbar serves as a support structure for the YBCO high-temperature superconducting tape; one end of the high-temperature superconducting current lead passes through the support plate and is connected to the second current lead, and the other end is fixed to the electrode fixed on the test sample plate.

[0008] Furthermore, the limiting groove extends to the electrode.

[0009] Furthermore, one end of the high-temperature superconducting current lead passes through the support plate and is fixed by an L-shaped bracket.

[0010] Furthermore, it also includes a power switch switching device, which comprises a self-locking relay circuit board, a DC relay, a magnetically shielded connecting wire, a DC power adapter, a remote control switch, a splitter, and a superconducting power supply. The remote control switch is equipped with multiple self-locking buttons, each button controlling the on / off state of a corresponding self-locking relay on the self-locking relay circuit board. The DC power adapter is connected to the self-locking relay circuit board to supply power. The DC power adapter is split into one positive and one negative terminal by the splitter. The split positive and negative terminals are connected to the splitter to form multiple positive and multiple negative terminals. Each positive terminal is connected to the common terminal of the self-locking relay on the self-locking relay circuit board via a magnetically shielded connecting wire. A wire is connected from the normally open terminal of the self-locking relay on the self-locking relay circuit board to the positive terminal of the corresponding DC relay, and then from the negative terminal of the DC relay to the negative terminal of the splitter, forming a complete circuit.

[0011] Furthermore, it also includes a Dewar, the sealing flange being sealed and fixed to the Dewar.

[0012] This invention also provides a method for testing the critical performance of superconducting wires in a high background field, applied to the aforementioned testing apparatus, characterized by comprising the following steps: Step 1: According to the test requirements, place the superconducting material in the limiting groove, and then weld the voltage signal line from the through groove onto the superconducting material. Step 2: Place the assembled test sample rod into the Dewar and seal it to the Dewar using the sealing flange; Step 3: Start the control circuit and perform a test; Step 4: When it is necessary to replace the superconducting material, pull out the test sample rod, replace the superconducting material and operate according to the method in Step 1; then disconnect the second current lead from the first current lead and the high-temperature superconducting current lead, pull it out from the hole in the support plate, replace the appropriate second current lead, connect it with the first current lead and the high-temperature superconducting current lead, and then execute Step 2 and Step 3.

[0013] The advantages of this invention are: The current leads are of a binary structure. The lower end of the current leads on the upper part of the sample rod can be disassembled and replaced according to the number and performance of the samples, greatly saving liquid helium. The power switch switching device is simple and easy to manufacture, and can switch the current leads under high background fields without field reduction, avoiding the labor and time consumption caused by field reduction and current lead replacement, while also saving liquid helium to a certain extent. The test sample plate of this invention has a circular structure, and the samples are placed radially with the center as the center point, making full use of the space of the cylindrical Dewar and accommodating multiple test samples. Attached Figure Description

[0014] Figure 1This is a schematic diagram of the overall mechanism of the test sample rod in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the assembly structure of the high-temperature superconducting current lead and the test sample plate in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the test sample plate mechanism in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the control circuit in Embodiment 2 of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] like Figure 1 As shown, a critical performance testing sample rod for high-current, multi-channel switchable superconducting wire in a high background field is disclosed. It includes a sealed flange 1, an aviation plug 2, a liquid helium return port 3, a liquid helium inlet 4, a room temperature terminal block 5, a first current lead 6, a stainless steel suspension rod 7, an epoxy support plate 8, a stainless steel support rod 9, a second current lead 10, a high-temperature superconducting current lead 11, an L-shaped support frame 12, an epoxy test sample plate 13, a first electrode 14, and a second electrode 15. The power switch switching device includes a self-locking relay circuit board 16, a DC relay, a magnetically shielded connecting wire 18, a DC power adapter, a remote control switch 20, a splitter, and a superconducting power supply 22.

[0017] The sealing flange 1 is equipped with an aviation plug 2, a liquid helium return port 3, a liquid helium inlet 4, and a room temperature terminal block. A stainless steel lifting rod 7 is threaded onto the sealing flange 1, serving as the core lifting structure for the test sample rod. The stainless steel lifting rod 7 passes sequentially through the central through-hole of the epoxy support plate 8, and is secured to the epoxy support plate at the top and bottom with nuts. The epoxy support plate 8 has evenly distributed circular through-holes on its periphery. The first current lead 6 passes sequentially through these circular through-holes and is spirally connected to the second current lead 10. The second current lead 10 has a smaller wire diameter than the upper first current lead 6, allowing it to be pulled out and replaced from the epoxy support plate 8. Simultaneously, the second current lead 10 is closer to liquid helium, meaning the lower part of the test sample rod has a lower temperature, significantly reducing copper resistance. This means that the second current lead 10, despite its smaller wire diameter, can withstand the same current as the upper first current lead 6. Furthermore, the number of second current leads 10 can be selectively increased or decreased depending on the number of samples. The lower end of the second current lead 10 is disconnected and connected to the high-temperature superconducting current lead 11. The high-temperature superconducting current lead 11 is an oxygen-free copper busbar with grooves. YBCO high-temperature superconducting tape is welded into the grooves. The oxygen-free copper busbar serves as a support structure for the YBCO high-temperature superconducting tape, and together they form the high-temperature superconducting section of the binary current lead. The upper end of the high-temperature superconducting current lead is connected to the epoxy board via an L-shaped bracket, and the lower end is connected to the electrode via bolts. The epoxy test sample plate 13 is a circular structure that, together with the first electrode 14 (negative electrode) and the second electrode 15 (positive electrode), forms the test sample plate. The epoxy test sample plate 13 has a rectangular limiting groove 131, such as... Figure 3 As shown, this design facilitates the placement of circular superconducting wires, while the inner wall of the limiting groove 131 also provides support for the superconducting wires, preventing them from bending due to electromagnetic forces under high background fields. Simultaneously, deeper through grooves 132 are formed at both ends of each rectangular limiting groove 131, allowing voltage signal lines to pass through and wrap around the superconducting wire before welding, avoiding the problem of difficult welding between the superconducting wire and voltage signal line due to small contact area. Grooves of the same size as the rectangular grooves are formed on the first electrode 14 and the second electrode 15, allowing the superconducting wires to be placed on the same horizontal plane. All grooves on the epoxy test sample plate 13 extend radially outward from the center, allowing for the placement of more samples.

[0018] The test sample board is connected to the high-temperature superconducting current lead 11 by bolts, which facilitates disassembly and sample replacement.

[0019] In addition, the power switch switching device consists of a self-locking relay circuit board 16, a DC relay, a magnetically shielded connecting wire 18, two DC power adapters, a remote control switch 20, a splitter, and a superconducting power supply 22. The remote control switch 20 is equipped with multiple self-locking buttons, each button controlling the on / off state of the corresponding self-locking relay on the control circuit board. Figure 4As shown, taking the testing of three superconducting wires as an example, the DC power adapter 19-1 is connected to the self-locking relay circuit board 16 to supply power to the circuit board. The DC power adapter 19-2 is split into one positive and one negative terminal by the splitter 21-1. The split positive and negative terminals are connected to the splitter 21-2, resulting in three positive and three negative terminals. Starting from one of the positive terminals, the magnetic shielding connection wire 18 is connected to the common terminal of the self-locking relay 16-1 on the control circuit board 16. From the normally open terminal of the relay 16-1 on the self-locking relay circuit board 16, a wire is connected to the positive terminal of the DC relay 17-1, and then from the negative terminal of the DC relay 17-1, a wire is connected to the negative terminal of the splitter 21-2, forming a complete loop. The remaining relay devices are connected in the same way. One end of the DC relay is connected to a copper busbar and connected to the negative terminal of the superconducting power supply 22. The other end of the DC relay is connected to the negative terminal of the test sample board, and the positive terminal of the test sample board is connected to the positive terminal of the superconducting power supply 22, thus forming a complete closed loop. The remote control switch 20 is equipped with three self-locking push-button switches, numbered 1, 2, and 3. These are connected to the self-locking relay circuit board 16 to control the on / off state of the corresponding relays. For example, pressing the self-locking button number 1 closes relay 16-1, which in turn closes DC relay 17-1, thus placing sample one in a complete circuit for testing. To test sample two, simply press button number 1 again, then button number 2. This opens relay 16-1 and DC relay 17-1, closes relay 16-2, and then closes DC relay 17-2, placing sample two in a complete circuit for testing. Testing sample three follows the same procedure using relays 16-3 and 17-3.

[0020] The above demonstration uses only three samples. In practice, the number of relays can be increased based on the number of samples to control multiple samples. Furthermore, using relays to control the circuit is reliable, low-cost, and easy to implement.

[0021] This embodiment employs a three-section design for the current leads (first current lead 6, second current lead 10, and high-temperature superconducting current lead 11). The design dimensions of the first current lead are generally sufficient for self-field testing of short samples of all current superconducting materials. The second current lead in the middle section is replaceable, allowing for addition, removal, or replacement based on the performance and number of samples. For example, when testing six samples at once, six second current leads can be selected. If testing three samples at once, only three second current leads need to be removed, reducing unnecessary heat leakage and thus saving liquid helium. Furthermore, if the estimated upper limit of the current for the sample under test is low, a thinner current lead can be used, again to reduce unnecessary heat leakage and save liquid helium.

[0022] Since the lower part of the sample holder is immersed in liquid helium, the smaller the volume of the lower part, the more liquid helium is saved. In this embodiment, selecting the appropriate wire diameter and number of second current leads based on the sample can greatly control costs.

[0023] Example 2 Based on the test rod of Embodiment 1 above, this embodiment also provides a test device, which further includes a Dewar, and the test rod is located inside the Dewar and is sealed and fixed to the Dewar by a sealing flange 1.

[0024] This embodiment also describes a critical performance testing method for superconducting wires in a high background field, applied to the aforementioned testing apparatus, characterized by comprising the following steps: Step 1: According to the test requirements, place the superconducting material in the limiting groove 131, and then wrap the voltage signal line around the superconducting material from the through groove 132 and then weld it. Step 2: Place the assembled test sample rod into the Dewar and seal it to the Dewar using sealing flange 1; Step 3: Start the control circuit and perform a test; Step 4: When it is necessary to replace the superconducting material, pull out the test sample rod, replace the superconducting material and operate according to the method in Step 1; then disconnect the second current lead 10 from the first current lead 6 and the high-temperature superconducting current lead 11, pull it out from the hole in the support plate 8, replace the appropriate second current lead 10 according to the performance and quantity of the superconducting material, connect it with the first current lead 6 and the high-temperature superconducting current lead 11, and then execute Step 2 and Step 3.

[0025] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A critical performance testing device for superconducting wires in a high background field, characterized in that, The test sample rod includes a sealing flange (1), an aviation plug (2), a liquid helium return port (3), a liquid helium inlet (4), and a room temperature terminal block (5) installed on one side of the sealing flange (1); a fixed hanger (7) on the other side of the sealing flange (1); multiple support plates (8) are arranged at intervals on the hanger (7); multiple through holes are opened on the support plates (8), the top end of the current lead is connected to the room temperature terminal block (5), and the bottom end passes through multiple support plates (8) and is detachably connected to a high temperature superconducting current lead (11); the current lead includes a first current lead (6) in the upper half and a second current lead (10) in the lower half; the first current lead (6) and the second current lead (10) are connected to each other. 0) Detachable connection, the diameter of the first current lead (6) is larger than that of the second current lead (10); multiple limiting grooves (131) are radially opened from the center of the test sample plate (13), and an electrode is fixed at one end of the multiple limiting grooves (131) away from the center of the test sample plate (13), and multiple high-temperature superconducting current leads (11) are connected to the corresponding electrodes; the high-temperature superconducting current lead (11) is an oxygen-free copper busbar with grooves; YBCO high-temperature superconducting tape is welded in the grooves, and the oxygen-free copper busbar serves as the support structure of the YBCO high-temperature superconducting tape; one end of the high-temperature superconducting current lead (11) passes through the support plate (8) and is connected to the second current lead (10), and the other end is fixed to the electrode fixed on the test sample plate (13).

2. The critical performance testing device for superconducting wires in a high background field according to claim 1, characterized in that, A through slot (132) for voltage signal lines to pass through is opened perpendicular to the limiting slot (131); the depth of the through slot (132) is greater than that of the limiting slot (131).

3. The critical performance testing device for superconducting wires in a high background field according to claim 1 or 2, characterized in that, The limiting groove (131) extends to the electrode.

4. The critical performance testing device for superconducting wires in a high background field according to claim 1, characterized in that, One end of the high-temperature superconducting current lead (11) passes through the support plate (8) and is fixed by an L-shaped bracket.

5. A critical performance testing device for superconducting wires in a high background field according to claim 1 or 2, characterized in that, The test sample plate (13) is circular, and the limiting groove (131) is radially and uniformly arranged on the test sample plate (13).

6. A critical performance testing device for superconducting wires in a high background field according to claim 1 or 2, characterized in that, It also includes a power switch switching device, which comprises a self-locking relay circuit board (16), a DC relay, a magnetically shielded connecting wire (18), a DC power adapter, a remote control switch (20), a splitter, and a superconducting power supply (22); the remote control switch (20) is equipped with multiple self-locking buttons, each button controlling the on / off state of the self-locking relay on the corresponding self-locking relay circuit board; the DC power adapter includes a first DC power adapter (19-1) and a second DC power adapter (19-2); the first DC power adapter (19-1) is connected to the self-locking relay circuit board (16) to supply power to the self-locking relay circuit board. The circuit board of the self-locking relay is powered; the second DC power adapter (19-2) is split into a positive terminal and a negative terminal by the first splitter (21-1); the split positive and negative terminals are connected to the second splitter (21-2) to split into multiple positive terminals and multiple negative terminals; each positive terminal is connected to the common terminal of the self-locking relay on the circuit board (16) of the self-locking relay through the magnetic shielded connecting wire (18), the normally open terminal of the self-locking relay on the circuit board (16) is connected to the positive terminal of the corresponding DC relay, and the negative terminal of the DC relay is connected to the negative terminal of the second splitter (21-2) to form a complete circuit.

7. The critical performance testing device for superconducting wires in a high background field according to claim 6, characterized in that, It also includes a Dewar, the sealing flange (1) being sealed and fixed to the Dewar.

8. A method for testing the critical performance of superconducting wires in a high background field, applied to the testing apparatus described in claim 7, characterized in that, Includes the following steps: Step 1: According to the test requirements, place the superconducting material in the limiting groove (131), and then weld the voltage signal line from the through groove (132) onto the superconducting material. Step 2: Place the assembled test sample rod into the Dewar and seal it to the Dewar using the sealing flange (1); Step 3: Start the control circuit and perform a test; Step 4: When it is necessary to replace the superconducting material, pull out the test sample rod, replace the superconducting material and operate according to the method in Step 1; then disconnect the second current lead (10) from the first current lead (6) and the high-temperature superconducting current lead (11), pull it out from the hole in the support plate (8), replace the appropriate second current lead (10), connect it with the first current lead (6) and the high-temperature superconducting current lead (11), and then execute Step 2 and Step 3.

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