JP5175653B2 - Superconducting magnet - Google Patents

Description

  The present invention relates to a superconducting magnet configured by winding a superconducting tape wire.

  In recent years, lengthy development of high-temperature superconducting wires excellent in critical current characteristics in a high magnetic field has been actively conducted, and application to high-field superconducting magnets is expected.

  Among high-temperature superconducting wires, high-temperature superconducting tape wires (coated conductors) are being applied to superconducting applications because high critical current densities can be obtained. The high-temperature superconducting tape wire is formed by forming an insulating intermediate layer on a tape-shaped metal substrate and forming an oxide superconductor layer thereon. Features of this high-temperature superconducting tape wire include excellent critical current density characteristics in a high magnetic field, high mechanical strength of the metal substrate portion, and the like. For example, Patent Document 1 describes a high-temperature superconducting magnet using a high-temperature superconducting tape wire.

A superconducting magnet can generate a stationary magnetic field with less energy loss than a normal conducting magnet. In the design of superconducting magnets, considering the magnetic field dependence of the critical current value, the so-called grading that divides the winding part into multiple radial layers according to the distribution of the empirical magnetic field reduces the amount of wire used and is efficient A magnetic field can be generated.
Japanese Patent Laid-Open No. 7-142245

  By the way, depending on the generated magnetic field and shape of the superconducting magnet, the upper limit of the current density is not limited to the magnetic field dependency (load factor) of the superconducting characteristics, and may be restricted by the allowable stress of the wire. When the superconducting application device to which the high temperature superconducting wire is applied is a high magnetic field magnet, the inner layer magnet (high magnetic field part) is shared by the high temperature superconducting magnet and the external magnetic field generated by the outer layer magnet is experienced. The inner layer magnet has a bore diameter of several centimeters, and the ratio of the inner and outer diameters of the magnet is large (compared to a large-diameter magnet). In such a configuration, the electromagnetic force (hoop force) applied to the superconducting wire increases from the inner diameter side to the outer diameter side, and the stress applied to the wire increases on the outer diameter side. In doing so, the allowable stress of the wire must be taken into account, which creates design constraints. Further, radial stress acts in the tensile direction, and stress in the peeling direction is applied to the wires and inclusions between the wires, which may cause cracks and deterioration of the superconducting characteristics of the wires.

  In addition, the above-mentioned patent document 1 considers the magnetic field dependence of the critical current characteristic of the high-temperature superconducting material, and changes the cross-sectional area of the high-temperature superconducting part for each unit of the high-temperature superconducting magnet in which a plurality of magnet units are laminated, This is a technique for realizing a high-temperature superconducting magnet having a high generated magnetic field by making the critical currents of the units substantially coincide with each other, and does not solve the above problems.

  Under conditions where the design is restricted by the allowable stress of the wire, a method of externally reinforcing the superconducting wire with a conduit or a method of internally reinforcing with a reinforcing material can be considered as a countermeasure against electromagnetic force. However, in the external reinforcement, there is a problem that it is difficult to uniformly transmit the electromagnetic force generated in the superconductor to the reinforcing material. Further, although internal reinforcement is performed with a compound superconducting wire or the like, there is also a problem that it is difficult to apply to a high-temperature superconducting wire.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a superconducting magnet that efficiently relaxes the stress distribution inside the winding.

The superconducting magnet according to the present invention is formed by winding a tape-shaped superconducting tape wire in a cylindrical shape, and is provided on the outer diameter side of the winding portion having a non-conductive material between the wires, comprising a supporting member supporting the winding unit, the elastic modulus of the non-conductive material, the superconducting is low rather configured than the elastic modulus of the tape wire, the winding unit includes a first positioned on the inner diameter side It has 1 winding part and a 2nd winding part located in an outer diameter side, and a current density lower than the said 1st winding part, It is characterized by the above-mentioned.

  According to the present invention, it is possible to provide a superconducting magnet that efficiently relaxes the stress distribution inside the winding.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram for explaining an example of the configuration of the superconducting magnet according to the first embodiment of the present invention. FIG. 1 shows a cross section of the superconducting magnet according to the embodiment, and shows an enlarged view of a part thereof.

  The superconducting magnet shown in FIG. 1 is a cylindrical magnet having a winding portion (coil) 1 and a support member 7, and can be applied to, for example, a high-temperature superconducting magnet in a high magnetic field magnet. The winding portion 1 is formed by winding a tape-shaped superconducting tape wire 2 into a cylindrical shape by a winding method called layer winding or pancake winding, and has a non-conductive material 3 between the wires. That is, the adjacent wires of the superconducting tape wire 2 are not in direct contact with each other, and the nonconductive material 3 is interposed between the wires. In particular, the elastic modulus of the non-conductive material 3 is lower than the elastic modulus of the superconducting tape wire 2, for example, about 1/10 of the elastic modulus of the superconducting tape wire 2. The support member 7 is provided on the outer diameter side of the winding part 1 and supports the winding part 1. The elastic modulus of the support member 7 is higher than the elastic modulus of the superconducting tape wire 2 and is, for example, about 10 times the elastic modulus of the superconducting tape wire 2.

  The superconducting tape wire 2 includes, for example, a tape-shaped metal substrate (such as Hastelloy), an intermediate layer (such as a polycrystalline thin film layer) formed on the metal substrate, and a superconducting layer (yttrium) formed on the intermediate layer. A high-temperature superconducting tape wire (coated conductor) composed of a highly conductive stabilized metal layer (such as silver) formed on the superconducting layer.

  The nonconductive material 3 may be a cured epoxy resin having a very low elastic modulus, or may be a non-adhesive material in which a nonconductive material is wound together with the superconducting tape wire 2.

  The support member 7 is preferably a non-magnetic high-strength material such as stainless steel or hastelloy.

  In particular, when the high-temperature superconducting magnet is cooled to a very low temperature, there is a merit that the temperature margin is sufficiently large and quenching due to mechanical disturbance is difficult to occur. Therefore, in this case, fixing of the winding part 1 by resin impregnation or the like is not important, and a configuration having a low elastic modulus like the nonconductive material 3 or not fixed like the superconducting tape wire 2 is allowed.

  According to the above configuration, since the elastic modulus of the nonconductive material 3 interposed between the wires of the superconducting tape wire 2 is small, the stress in the radial direction due to the stress generated in each turn of the superconducting tape wire 2 reaching the adjacent turn. The peak value can be relaxed. In the superconducting magnet formed by winding a high-temperature superconducting tape wire, particularly an yttrium-based superconducting tape wire, particularly as the superconducting tape wire 2, since the radial tensile stress in the winding portion 1 works in the peeling direction of the wire to be wound. It is possible to generate a high magnetic field without deteriorating the wire properties. Moreover, since the member 7 is attached to the outer diameter side of the winding part 1, it becomes possible to suppress the radial displacement at the time of excitation.

(Second Embodiment)
FIG. 2 is a diagram for explaining an example of the configuration of the superconducting magnet according to the second embodiment of the present invention. FIG. 2 shows a cross-section of the superconducting magnet according to the same embodiment, and shows an enlarged view of a part thereof. In addition, the same code | symbol is attached | subjected to the element which is common in FIG. 1, and the description is abbreviate | omitted. Below, it demonstrates centering on a different part from 1st Embodiment.

  The superconducting magnet shown in FIG. 2 has a configuration in which the winding portion 1 further includes a flat flange 8 in the configuration of the superconducting magnet shown in FIG.

  The flange 8 prevents each turn of the superconducting tape wire 2 from being separately displaced in the axial direction.

  The material of the flange 8 may be an insulator such as fiber reinforced plastic (FRP) or mica, or a nonmagnetic metal plate that is electrically insulated in consideration of the withstand voltage between pancakes. Also good.

  The flange 8 presses the upper and lower ends of each turn of the superconducting tape wire 2 but is not necessarily connected to each turn of the superconducting tape wire 2 and is movable with respect to the axial direction of the superconducting magnet. As a result, the flange 8 is constrained to be displaced in units of pancake against stress in the axial direction while allowing each turn of the superconducting tape wire 2 to be individually displaced in the radial direction of the superconducting magnet. Can do. That is, individual turns existing from the inner diameter side to the outer diameter side of the winding part 1 displaced by the electromagnetic force can be displaced while being aligned in the axial direction, and can be excited while avoiding positional deviation in the axial direction. Become.

  In addition, the flange 8 shown in the embodiment can be applied to each winding portion of each embodiment (FIGS. 3 to 7 and the like) described later.

(Third embodiment)
FIG. 3 is a diagram for explaining an example of the configuration of a superconducting magnet according to the third embodiment of the present invention. FIG. 3 shows a cross section of the superconducting magnet according to the embodiment, and shows an enlarged view of a part thereof. In addition, the same code | symbol is attached | subjected to the element which is common in FIG. 1, and the description is abbreviate | omitted. Further, although the support member 7 is not shown in FIG. 3, it is assumed that it actually exists. Below, it demonstrates centering on a different part from 1st Embodiment.

  The superconducting magnet shown in FIG. 3 is the same as the superconducting magnet shown in FIG. 1, but the winding part 1 further includes a first winding part 11, a second winding part 12, and a third winding part. 13 is provided.

  The first winding part 11 is a coil part located on the inner diameter side of the superconducting magnet.

  The second winding portion 12 is a coil portion that is located in the central portion of the superconducting magnet and has a current density lower than that of the first winding portion 11.

  The third winding portion 13 is a coil portion located on the outer diameter side of the superconducting magnet and having a lower current density than the second winding portion 12.

  That is, the current density is lower on the outer diameter side than on the inner diameter side of the superconducting magnet.

  According to the above configuration, it is possible to efficiently prevent the stress on the outer diameter side of the magnet from becoming excessive, and to reduce the stress applied in the peeling direction of the superconducting tape wire 2 to an allowable value or less. In addition, although the case where the plurality of winding portions constituting the winding portion 1 is three is illustrated here, the present invention is not limited to this, and the plurality of winding portions constituting the winding portion 1 is two. Or four or more. Further, as the superconducting magnet is moved from the inner diameter side toward the outer diameter side, the current density may be gradually decreased instead of gradually decreasing.

(Fourth embodiment)
FIG. 4 is a diagram for explaining an example of the configuration of a superconducting magnet according to the fourth embodiment of the present invention. The superconducting magnet shown in FIG. 4 shows an example of a specific configuration for realizing a plurality of winding portions having different current densities in the superconducting magnet shown in FIG.

  A winding portion (for example, corresponding to the first winding portion 11 described above) located on the inner diameter side of the superconducting magnet is wound around a wire 21.

  A winding portion (e.g., corresponding to the second winding portion 12 described above) located at the center of the superconducting magnet is wound with a wire 22 having a width wider than that of the wire 21.

  A winding portion (e.g., corresponding to the third winding portion 13 described above) located on the outer diameter side of the superconducting magnet is wound with a wire 23 having a width wider than that of the wire 22.

  According to the above configuration, by preparing the wire rods 21, 22, and 23 having different widths, it is possible to easily realize a configuration in which the current density decreases from the inner diameter side to the outer diameter side of the superconducting magnet.

  Note that the wire rods 21, 22, and 23 having different widths shown in the embodiment can be applied to each winding portion of each embodiment (FIGS. 5 to 7 and the like) described later.

(Fifth embodiment)
FIG. 5 is a diagram for explaining an example of the configuration of a superconducting magnet according to the fifth embodiment of the present invention. The superconducting magnet shown in FIG. 5 shows another example of a specific configuration for realizing a plurality of winding portions having different current densities in the superconducting magnet shown in FIG.

  A winding portion (e.g., corresponding to the first winding portion 11 described above) located on the inner diameter side of the superconducting magnet has a nonconductive material 31 between the wires of the superconducting tape wire 2.

  A winding portion (e.g., corresponding to the second winding portion 12 described above) located at the center of the superconducting magnet has a nonconductive material 32 thicker than the nonconductive material 31 between the wires of the superconducting tape wire 2. Have.

  A winding portion (e.g., corresponding to the third winding portion 13 described above) located on the outer diameter side of the superconducting magnet has a non-conductive material 33 thicker than the non-conductive material 32 between the wires of the superconducting tape wire 2. Have

  According to the above configuration, by preparing the non-conductive materials 31, 32, and 33 having different thicknesses, it is possible to easily realize a configuration in which the current density decreases from the inner diameter side to the outer diameter side of the superconducting magnet. It becomes possible.

  In addition, the nonconductive materials 31, 32, and 33 having different thicknesses shown in the embodiment can be applied to each winding portion in each embodiment (FIGS. 6, 7, etc.) described later.

(Sixth embodiment)
FIG. 6 is a diagram for explaining an example of the configuration of a superconducting magnet according to the sixth embodiment of the present invention. The superconducting magnet shown in FIG. 6 shows an example in which fibers 4 are used as the nonconductive material 3 in the superconducting magnet shown in FIG.

  The fiber 4 is used as an example of the non-conductive material 3 described above, and includes at least one of glass fiber, polymer fiber, and pulp (fiber made from wood, paper, or the like). The fibers 4 are arranged so that the direction of the fibers is parallel to the longitudinal direction of the superconducting tape wire 2. When a plurality of fibers are bundled and used, the fibers may be in a non-bonded state, but the peak value of the radial stress is more effectively reduced by interposing a resin having a very low elastic modulus. And cracking of the resin can be suppressed.

  According to the above configuration, even when the fiber 4 is used as the non-conductive material 3, it is possible to effectively relieve the radial stress.

  In addition, the fiber 4 shown in the embodiment can be applied to each winding portion of the above-described embodiments (FIGS. 2 to 5) and an embodiment (FIG. 7) described later.

(Seventh embodiment)
FIG. 7 is a diagram for explaining an example of the configuration of a superconducting magnet according to the seventh embodiment of the present invention. The superconducting magnet shown in FIG. 7 is positioned outside the concentric circle with respect to the first magnet element in addition to the superconducting magnet shown in FIG. 1 (hereinafter referred to as “first magnet element”). 1 shows an example of a configuration of a superconducting magnet further having a second magnet element and a third magnet element. Although the support member 7 is not shown in FIG. 7, the support member 7 may be provided in each magnet element or any one of the magnet elements.

  The 1st magnet element 14 comprises the inner layer magnet which has the above-mentioned winding part 1 and support member 7, for example.

  The second magnet elements 15 and 16 are provided hierarchically on the outer side of the concentric circle with respect to the first magnet element 14. In particular, the set of second magnet elements 15 and 16 is configured to generate a magnetic field in the same direction as the magnetic field generated by the first magnet element 14.

The second magnet elements 15 and 16 constitute cylindrical middle-layer magnets and outer-layer magnets around which metal / compound superconducting wires such as NbTi and Nb ₃ Sn are wound, and are excited in combination.

  In the configuration in which a plurality of cylindrical magnet elements are nested as shown in FIG. 7, the empirical magnetic field of the high-temperature superconducting magnet is distributed in the same direction over the inner and outer diameters and approximately linearly in the radial direction. When excited under an external magnetic field condition in which the ratio of the empirical magnetic field in the inner and outer diameter portions is positive, the radial stress inside the winding due to excitation becomes a positive value in the entire area, and stress is applied in the peeling direction of the wire. The configuration in which the elastic modulus of the inclusions between the wires is lowered effectively acts to reduce the peeling direction stress.

  FIG. 8 is a diagram for explaining an example of the magnetic field distribution in the superconducting magnet common to the first to sixth embodiments of the present invention. FIG. 8 shows an empirical magnetic field 61 and an empirical magnetic field 62 at an inner diameter position 51 and an outer diameter position 52 in the radial direction from the central axis of the superconducting magnet (or winding portion 1), and the magnetic field distribution including them is shown. It is shown. This magnetic field distribution can serve as a guideline for determining the radial position r that determines the boundary between the winding portions 11, 12, and 13, for example.

  For example, the inner diameter position in the radial direction from the central axis of the superconducting magnet (or winding part 1) is r1 [m], the outer diameter position is r2 [m], and the empirical magnetic field at each position is B1 [T], B2 [T], the gradient obtained by linear approximation of the magnetic field distribution from B1 to B2 is a [T / m], and the magnetic field obtained by extrapolating the gradient a to the central axis of the superconducting magnet (or winding part 1) Let B0 [T], and let c be a constant corresponding to the upper limit of stress. At this time, the superconducting magnet (or the winding portion 1) has a function J = c / {(a × r + B0) × in which the current density J [A · m ^ −2] at an arbitrary radial position r [m] is r. r} is not exceeded.

  In the conventional impregnated magnet, generally, the upper limit index of the circumferential electromagnetic force is about 200 MPa. However, in each embodiment of the present invention, a high stress upper limit of 300 MPa can be set as the elastic limit of the superconducting tape wire. This makes it possible to design a compact superconducting magnet with higher current density.

  FIG. 9 is a diagram illustrating an example of a calculated value of the radial stress distribution in which the center of the conventional superconducting magnet is 0 [m]. On the other hand, FIG. 10 shows the center of the high-field superconducting magnet when the elastic modulus of the inclusions between the wires is reduced by about two orders of magnitude (about 1/100) according to the first embodiment of the present invention. It is a figure which shows an example of the calculation result of radial direction stress distribution made into 0 [m]. According to the calculation, the peak value of the radial stress can be effectively reduced by lowering the elastic modulus in the radial direction of the inclusions between the wires than the elastic modulus of the wire.

  Next, an example of a design for the superconducting magnet according to the above-described fourth embodiment of the present invention will be described with reference to FIGS. 11 and 12.

  FIG. 11 is an example of a table showing specifications of three winding portions (coils A, B, C) respectively corresponding to the wires 21, 22, 23 having different widths in the superconducting magnet according to the fourth embodiment of the present invention. FIG. FIG. 12 is a diagram showing an example of a graph showing the relationship between the hoop stress and the radial position of the superconducting magnet based on the specification shown in FIG.

  In this example, the width of the wire is increased from the coil A on the inner diameter side toward the coil C on the outer diameter side, thereby adjusting the current density J to be smaller.

  In this design example, the hoop stress BJr of the coil increases toward the outer diameter side. When the upper limit of the stress is c = 200 MPa, the appropriate position r where the current density J should be reduced can be determined by using the above-described formula J = c / {(a × r + B0) × r}. In an actual coil, BJr and the circumferential stress do not match due to the influence of the wire adjacent in the radial direction, but the peak value of the stress can be controlled by using the above equation.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of components disclosed in the first to seventh embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 1st Embodiment of this invention. The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 2nd Embodiment of this invention. The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 3rd Embodiment of this invention. The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 4th Embodiment of this invention. The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 5th Embodiment of this invention. The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 6th Embodiment of this invention. The figure for demonstrating an example of a structure of the superconducting magnet which concerns on the 7th Embodiment of this invention. The figure for demonstrating an example of the magnetic field distribution in the superconducting magnet common to the 1st-6th embodiment of this invention. The figure which shows an example of the calculated value of radial direction stress distribution which made the center of the conventional superconducting magnet 0 [m]. The figure which shows an example of the calculation result of radial direction stress distribution which set the center of the high magnetic field superconducting magnet to 0 [m] at the time of making the elasticity modulus of the inclusion between wires based on the 1st Embodiment of this invention small. The figure which shows an example of the table which shows the specification of three coil | winding parts (coil A, B, C) each corresponding to the wire 21, 21, 23 from which the width | variety differs in the superconducting magnet which concerns on the 4th Embodiment of this invention. The figure which shows an example of the graph which shows the relationship between the hoop stress-diameter direction position of the superconducting magnet based on the specification shown by FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,11-13 ... Winding part, 14-16 ... Magnet element, 2, 21-23 ... Superconducting tape wire, 3, 31-33 ... Nonelectroconductive material, 4 ... Fiber, 51 ... Inner diameter position, 52 ... Outside Diameter position, 61 ... Experience magnetic field at the inner diameter position, 62 ... Experience magnetic field at the outer diameter position, 7 ... Support member, 8 ... Flange.

Claims (8)

A winding part comprising a tape-shaped superconducting tape wire wound into a cylindrical shape and having a non-conductive material between the wires;
Provided on the outer diameter side of the winding portion, and a support member for supporting the winding portion,
The elastic modulus of the non-conductive material, the low rather configured than the elastic modulus of the superconducting tape,
The winding portion is
A first winding portion located on the inner diameter side;
A second winding portion located on the outer diameter side and having a current density lower than that of the first winding portion;
Superconducting magnet and having a. The superconducting tape wire is
A tape-shaped metal substrate;
A polycrystalline thin film layer formed on the metal substrate;
A superconducting layer formed on the polycrystalline thin film;
The superconducting magnet according to claim 1, further comprising a highly conductive stabilized metal layer formed on the superconducting layer.   The superconducting magnet according to claim 1, wherein the winding portion has a flange that inhibits each turn of the superconducting tape wire from being displaced separately in the axial direction. It said second winding portion superconducting tape in the superconducting magnet according to claim 1, characterized in that wider than the superconducting tape in said first winding portion. The non-conductive material in the second winding section, the superconducting magnet according to claim 1, wherein the thicker than the non-conductive material in said first winding portion. The superconducting magnet according to any one of claims 1 to 5 , wherein the non-conductive material includes at least one of glass fiber, polymer fiber, and pulp. A magnet element constituted by the winding part and the support member;
One or a plurality of other magnet elements that are located on the outer side of the concentric circle with respect to the magnet element and generate a magnetic field in the same direction as the magnetic field generated by the magnet element. The superconducting magnet according to any one of 1 to 6 . The inner diameter position in the radial direction from the central axis of the superconducting magnet is r1 [m], the outer diameter position is r2 [m], and the empirical magnetic fields at the respective positions are B1 [T] and B2 [T]. The gradient obtained by linear approximation of the magnetic field distribution up to B2 is a [T / m], the magnetic field obtained by extrapolating the gradient a to the central axis of the superconducting magnet is B0 [T], and a constant corresponding to the upper limit of the stress is set. When c, the current density J [A · m ^ −2] at an arbitrary position r [m] in the radial direction does not exceed the function J = c / {(a × r + B0) × r} of r. superconducting magnet according to any one of claims 1 to 7, characterized in that it is.

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