A multi-connected high-temperature superconducting magnet based on ReBCO-coated superconducting sheets

Abstract

The present invention relates to a multi-connected high-temperature superconducting magnet based on ReBCO-coated superconducting sheets that can simultaneously generate multiple magnetic induction intensities. The superconducting magnet is formed by alternately stacking and fixing one or more sets of superconducting ring sheets and insulating sheets. Several connected circular ring structures with successively decreasing radii are cut out on the superconducting sheets and insulating sheets, and the circular ring structures at corresponding positions have the same size. The present invention adopts a superconducting sheet stacking method, eliminating the bending and winding steps to reduce the impact on the performance of the superconducting tape; at the same time, the device adopts the existing "field cooling method" for excitation, without the need for welding, power supply and current leads, reducing operating costs and heat leakage, and has the advantages of compact structure, detachability, high stability and simple preparation process; it can stably output multiple stable magnetic fields with different magnetic induction intensities, expanding the scope of application of ReBCO superconductors in magnets, and can also be applied to application scenarios such as medium and large superconducting magnets.

Description

Technical Field

[0001] The present invention belongs to the field of superconducting magnet applications, and in particular relates to a multi-connected superconducting magnet based on ReBCO-coated superconducting sheets. Background Art

[0002] Strong magnetic fields are an important direction of current scientific research. Designing strong magnetic field test equipment to generate higher intensity magnetic fields is of great significance to the development of science and technology.

[0003] As an important part of the superconducting application field, superconducting magnets are used in many strong magnetic field occasions, such as superconducting tokamaks, superconducting motors, high-energy accelerators, etc., due to their advantages over conventional magnets, such as high magnetic field intensity, low power loss, and strong stability.

[0004] With the continuous advancement of manufacturing technology, ReBCO (rare earth barium copper oxide, Re is Y, Sm or Nd) coated conductors are widely used in practical engineering fields. ReBCO coated conductors have the advantages of high upper critical magnetic field, high critical current density, low AC loss, and excellent mechanical properties. Their good high-field performance and electromagnetic properties under external fields are suitable for the manufacture of superconducting magnet devices.

[0005] Currently, practical high-temperature superconducting wires are all in the form of thin ribbons, mechanically bent and twisted into double-pancake or toroidal structures. The joints of the superconducting ribbons require welding, but the immaturity of the non-resistance welding process prevents closed-loop operation of ReBCO superconducting magnets.

[0006] Existing superconducting magnets often use a power supply in a room temperature environment for excitation. The power supply and superconductor are connected by current leads. The two ends of the current leads are in low temperature and room temperature environments respectively. The large temperature difference causes a large amount of heat to be transferred into the superconducting low-temperature container. At the same time, the current lead resistance and the welding resistance between the current lead and the superconducting wire will also generate a large amount of Joule heat when power is applied, increasing the refrigeration efficiency load and increasing cooling and operating costs. Summary of the Invention

[0007] The object of the present invention is to provide a multi-connected superconducting magnet based on ReBCO-coated superconducting ring segments that can generate multiple magnetic fields simultaneously.

[0008] The superconducting magnet is characterized in that several interconnected circular ring structures with decreasing radius are cut out of the superconducting sheet and the insulating sheet, and the circular ring structures at corresponding positions of the two sheets have the same size; N+1 insulating sheets and N superconducting sheets are alternately stacked, flanges are added at the top and bottom, and the superconducting magnet is formed by fixing them with insulating rods, where N is a positive integer;

[0009] Among them, the stacking directions of the N ReBCO superconducting ring sheets in the superconducting magnet are all consistent.

[0010] The insulating sheet in the superconducting magnet is an organic insulating sheet, kraft paper or epoxy sheet.

[0011] The fixing device is made of stainless steel, epoxy fiberglass or epoxy resin; the fixing device includes flanges, bolts and nuts.

[0012] Among them, the superconducting magnet is excited by an excitation coil, which is made of copper wire wound on the iron core column; the specific operation is: the excitation coil is placed in the circular ring with the largest radius of the superconducting magnet, and the excitation coil is powered by a DC power supply at room temperature to generate a stable magnetic flux in the superconducting ring, and then the ambient temperature is lowered to make the superconducting magnet enter the superconducting state from the room temperature state. After reaching the target temperature, the excitation current is gradually reduced to zero. Due to the conservation of magnetic flux in closed-loop superconductors, a stable induced current will be generated in the superconducting ring to maintain the total magnetic flux in the closed loop of the superconducting magnet unchanged, thereby generating and maintaining stable magnetic fields of different intensities in each circular ring.

[0013] The superconducting magnet is cooled by immersion cooling in liquid nitrogen, immersion cooling in liquid helium, or other cooling media, or by conduction cooling.

[0014] The diameter of the excitation coil is slightly smaller than the diameter of the largest circular ring on the superconducting ring piece.

[0015] For the ReBCO superconducting ring segments provided by the present invention, which have five radii of different decreasing sizes and different center positions, when in use, it is only necessary to insert an excitation coil into the ring with the largest radius for overall excitation, and stable magnetic fields of different intensities can be obtained in the remaining rings.

[0016] The beneficial effects of the present invention are:

[0017] This invention breaks the original design idea of ​​"using one magnet to generate a magnetic field". By cutting circular ring pieces with different radii on the superconducting sheet, the purpose of exciting multiple holes with one hole to generate stable magnetic fields of different intensities is achieved. This also provides a new idea for the design of superconducting magnets.

[0018] The present invention is formed by alternately stacking superconducting sheets and insulating sheets, eliminating the need for bending and winding steps, having little effect on the flow capacity of the superconducting material, and is easy to manufacture, has a simple structure, and has no bending radius restrictions.

[0019] The present invention adopts the "field cooling method" for excitation, inducing a stable current in the superconducting magnet, realizing the resistance-free closed-loop operation of the superconducting magnet and having a high current-carrying capacity; without the need for welding processes or current leads, the superconducting magnet structure is compact while reducing the heat loss of the superconducting magnet. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Attachment Figure 1 Schematic diagram of the ReBCO superconducting ring structure;

[0021] Explanation of reference numerals: 101 - 1st circular hole; 102 - 2nd circular hole; 103 - 3rd circular hole; 104 - 4th circular hole; 105 - 5th circular hole;

[0022] Attachment Figure 2 Schematic diagram of the insulating sheet;

[0023] Attachment Figure 3 Schematic diagram of a multi-connected superconducting magnet based on ReBCO-coated superconducting sheets;

[0024] Explanation of reference numbers: 4-flange; 5-flange positioning hole; 6-bolt; 7-nut; 8-excitation coil; 9-DC power supply;

[0025] Attachment Figure 4 This is the current source waveform. DETAILED DESCRIPTION

[0026] The present invention provides a multi-connected superconducting magnet based on ReBCO superconducting sheets, which will be further described below with reference to embodiments and accompanying drawings.

[0027] 1. As attached Figure 1 , prepare ReBCO square superconducting ring piece 1, the specific process is as follows:

[0028] Among them, Figure 1 The specific preparation process of the ReBCO square superconducting ring sheet consisting of five separated circular rings is as follows:

[0029] Cut the existing ReBCO superconducting sheet into square sheets. Then, cut out five circular rings with a width of d1 and inner diameters of r1, r2, r3, r4, and r5 at appropriate locations inside the square sheet. These rings are marked as 101, 102, 103, 104, and 105, respectively. At the same time, cut out slits with a width of w1 (less than 1 mm) and a length of l1 (not less than d1) at the line connecting the centers of adjacent circular holes to connect the adjacent circular holes. Figure 1 The ReBCO square superconducting ring piece 1 is shown.

[0030] The ReBCO square superconducting ring piece is preferably an axisymmetric ring piece, and the size requirements of each part are as follows: r1, r2, r3, r4, and r5 decrease in sequence.

[0031] 2. As attached Figure 2 , prepare insulating sheet 2: cut an organic insulating film such as PPLP insulating material film, kraft paper or epoxy sheet into insulating sheet 2 with the same shape and size as the above-mentioned superconducting ring sheet. The difference from the superconducting sheet is that there is no cutting gap between the rings.

[0032] 3. As attached Figure 3, prepare superconducting magnets, the specific process is:

[0033] (1) Place the first square insulating sheet horizontally, then stack the first ReBCO square superconducting ring sheet on top of the insulating sheet, making sure that they are completely aligned up and down and left and right.

[0034] (2) Similarly, stack the second square insulating sheet, the second ReBCO square superconducting ring sheet, ..., the Nth square insulating sheet, the Nth ReBCO square superconducting ring sheet, and the N+1th square insulating sheet; wherein the stacking directions of the N ReBCO square superconducting ring sheets are all consistent;

[0035] (3) After stacking is completed, flanges 4 are added on the top and bottom to fix them, and bolts 6 and nuts 7 are used to press and fix the superconducting ring pieces and the insulating pieces through the flange positioning holes 5 to form a superconducting magnet; the size of the opening inside the flange 4 is exactly the same as that of the hole inside the stack;

[0036] (4) The closed-loop operation of the superconducting magnet is realized by using the excitation coil through field cooling excitation. Specifically, the excitation coil with the iron core is first inserted into the ring 101 with the largest radius inside the superconducting magnet. After the device is fixed, a DC power supply 9 is used to provide DC current to the excitation coil 8 at room temperature, as shown in the attached figure. Figure 4 Phase I (0-t1): Starting at time 0, the excitation current gradually increases, reaching the target value I0 at time t. Phase II (t1-t2): The excitation current is maintained constant, and the superconducting magnet is cooled to the target temperature for the superconducting state. Phase III (t2-t3): The excitation current is gradually reduced, reaching zero at time t. At this point, a stable induced current is generated in the superconducting ring segments, maintaining the total magnetic flux within the closed loop of the superconducting magnet constant, thereby generating a stable magnetic field with different magnetic induction strengths within each ring.

[0037] The outer radius of the excitation coil 8 is slightly smaller than the radius of the inner hole 101 of the superconducting magnet, and the height of the excitation coil 8 is greater than the height of the superconducting magnet.

[0038] The high-temperature superconducting magnet with five circular holes described above is merely an example of a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Superconducting magnets with other numbers of holes, shapes of holes (such as square holes, rectangular holes, and elliptical holes), and superconducting magnets composed of superconducting sheets made of other materials are also within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-temperature superconducting magnet based on ReBCO superconducting ring segments, characterized in that: The superconducting magnet comprises superconducting rings and insulating sheets stacked directly, an excitation coil placed and fixed in the largest circular hole of the magnet, two leads extending from the excitation coil connected to an external DC power supply, and a magnetic field generated by the excitation coil to achieve closed-loop superconducting operation of the magnet. The magnet itself is formed by alternately stacking and fixing N ReBCO superconducting rings and N+1 insulating sheets, where N is a positive integer; the N+1 insulating sheets have the same shape and size as the N ReBCO superconducting rings; and the rings are composed of a plurality of circular rings with different center positions connected by slits. For a ReBCO superconducting ring segment composed of several rings with different center positions and different radii, during operation, an excitation coil is passed through the ring with the largest radius to excite the entire magnet, generating different magnetic fields in the remaining rings. The superconducting magnet utilizes internal excitation of the excitation coil. The specific operation is as follows: the excitation coil is placed in the circular ring with the largest radius of the superconducting magnet, and the excitation coil is powered by a DC power supply at room temperature to generate a stable magnetic flux in the superconducting ring. Then, the magnet temperature is lowered to make the superconducting magnet enter the superconducting state from the room temperature state. After stabilization, the excitation current is gradually reduced to zero. Due to the conservation of magnetic flux in closed-loop superconductors, a stable induced current is generated in the superconducting ring segments to maintain the closed-loop operation of the superconducting magnet, thereby generating and maintaining a stable magnetic field of different strengths at the center of each circular ring.

2. The superconducting magnet according to claim 1, characterized in that The plurality of annular areas with different center positions and different radii are connected to each other, and a very narrow gap is opened at the connection between adjacent annular areas.

3. The superconducting magnet according to claim 1, wherein The N ReBCO superconducting ring sheets and N+1 insulating sheets are alternately stacked. The insulating sheets are organic insulating films, kraft paper or epoxy sheets. Their sizes are the same as the superconducting ring sheets and they are distributed with circular structures with the same positions and sizes as the superconducting sheets.

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