Superconducting magnet, superconducting wire and method for producing superconducting magnet

Abstract

A superconducting magnet that can be constructed cheaply is realized. To this end, a superconducting magnet (100) comprises: a magnet portion (1) on which a first superconducting wire (50) is wound, the first superconducting wire (50) having a superconducting material portion, a high-resistance conductor layer, and a low-resistance conductor layer having a lower resistance per unit length than the high-resistance conductor layer; and a current switch (30) including a second superconducting wire (52) having a superconducting material portion and a high-resistance conductor layer, the second superconducting wire (52) not containing a low-resistance conductor layer, or having a low-resistance conductor layer that is formed thinner than the low-resistance conductor layer in the first superconducting wire (50).

Description

Technical Field

[0001] The present invention relates to a superconducting magnet, a superconducting wire and a method for producing the superconducting magnet. Background Art

[0002] As background technology in this technical field, in paragraph 0019 of the specification of the following patent document 1, it is recorded: "A superconducting coil S1 is produced by winding a non-connected superconducting wire 1 around a coil skeleton C, and a heating wire H is wound around a portion of the same wire. The portion around which the heating wire H is wound is made into a superconducting coil S2 by non-inductive winding. The superconducting coil S2 is used as a thermal constant current switch. While the entire superconducting coil is immersed in a refrigerant, an electric current is passed through the heating wire H of the superconducting coil S2 to heat it to above the superconducting transition temperature, thereby destroying the superconducting state. In this state, if power is supplied from electrodes PL1 and PL2, the superconducting coil S1 can be excited."

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-176338 Summary of the invention

[0006] In addition, a constant current switch is often provided in a superconducting magnet as described in Patent Document 1. However, there is a problem that the cost of the superconducting magnet increases greatly due to the provision of the constant current switch.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a superconducting magnet, a superconducting wire, and a method for producing a superconducting magnet that can be constructed inexpensively.

[0008] In order to solve the above-mentioned problems, the superconducting magnet of the present invention is characterized in that it comprises: a magnet portion, which is wound with a first superconducting wire, and the first superconducting wire has a superconducting material portion, a high-resistance conductor layer and a low-resistance conductor layer whose resistance per unit length is lower than that of the above-mentioned high-resistance conductor layer; and a current switch, which includes a second superconducting wire, and the second superconducting wire has the above-mentioned superconducting material portion and the above-mentioned high-resistance conductor layer, and the above-mentioned second superconducting wire does not contain the above-mentioned low-resistance conductor layer, or has the above-mentioned low-resistance conductor layer that is formed thinner than the above-mentioned low-resistance conductor layer in the above-mentioned first superconducting wire.

[0009] Effects of the Invention

[0010] According to the present invention, a superconducting magnet, a superconducting wire, and a method for producing a superconducting magnet that can be constructed inexpensively can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic circuit diagram of a superconducting magnet according to a preferred first embodiment.

[0012] Figure 2 yes Figure 1 Sectional view II-II in FIG.

[0013] Figure 3 yes Figure 1 Section view III-III in FIG.

[0014] Figure 4 This is a schematic circuit diagram of a superconducting magnet according to a preferred second embodiment.

[0015] Figure 5 It is a diagram showing another arrangement method of the second superconducting wire in the PCS.

[0016] Figure 6 It is a diagram showing still another arrangement method of the second superconducting wire in the PCS.

[0017] Figure 7 It is a cross-sectional view of a main part of a superconducting magnet according to a preferred third embodiment.

[0018] Figure 8 This is a schematic circuit diagram of a superconducting magnet according to a preferred fourth embodiment.

[0019] Fig. 9 yes Figure 8 IX-IX cross-sectional view of the superconducting wire in FIG.

[0020] Fig.10 yes Figure 8 XX cross-sectional view of the superconducting wire in.

[0021] Fig.11 This is a schematic circuit diagram of a superconducting magnet according to a preferred fifth embodiment.

[0022] Fig.12 This is a schematic circuit diagram of a superconducting magnet 110 according to a preferred sixth embodiment. DETAILED DESCRIPTION

[0023] [Prerequisites of implementation method]

[0024] Superconducting magnets using superconducting wires are used in MRI (Magnetic Resonance Imaging), NMR (nuclear magnetic resonance), particle beam medical devices, etc., and their application to electric motors is also being studied every day. Superconducting magnets have the characteristic that no loss occurs even when a direct current is passed through the superconducting wire, so they can be operated in a so-called constant current mode in which a closed circuit including the superconducting magnet is constructed in a superconducting manner and a direct current is continuously passed through. In the constant current mode, the superconducting magnet can maintain its magnetic field without connecting a power source for passing a current through the superconducting magnet.

[0025] Normally, the constant current mode operation is performed in a device that is provided with a closed circuit that connects the superconducting magnet and the excitation power supply to supply the excitation current to the superconducting magnet, and a closed circuit that connects the superconducting magnet and the PCS (Persistent Current Switch) superconductingly to pass a constant current. That is, the excitation current is applied to the superconducting magnet from the excitation power supply while the PCS is in a normal conductive state, and when the excitation current reaches a desired value, the PCS is put into a superconducting state and the excitation power supply is disconnected from the superconducting magnet in the circuit.

[0026] Conversely, when the superconducting magnet is demagnetized, the PCS is converted to the normal conductive state. The method adopts a method such as heating the superconducting wire with a heater or applying a magnetic field to the superconducting wire. The time required for excitation demagnetization depends on the time constant (=L / R) determined by the inductance L of the superconducting magnet and the electrical resistance (hereinafter referred to as resistance) R of the PCS in the normal conductive state. How to set the time constant is usually determined by the specifications of the superconducting magnet application equipment, and the PCS in the normal conductive state is required to have a desired resistance.

[0027] The resistance value of the PCS in the normal conducting state is determined by the electrical resistivity (hereinafter referred to as resistivity) of the material constituting the superconducting wire used in the PCS, the cross-sectional dimensions and the length. Usually, the superconducting wire is realized by making Cu, Al, Ag or an alloy based on these metals into a tubular shape and filling the inside with a superconducting material, or stacking these metals and superconducting materials in a strip shape. That is, the cross section of the superconducting wire usually contains superconducting materials and metals. Metals have the function of serving as stabilizing materials for superconducting wires, and metals as stabilizing materials are required to have low resistance. On the other hand, since the PCS is required to have the desired resistance in the normal conducting state as described above, when the PCS is constituted by the same superconducting wire as the superconducting magnet, the problem of the length of the PCS wire becoming longer will arise.

[0028] In order to shorten the wire length of PCS, there is a method of increasing the resistance per unit length by using a metal with high resistivity (such as Cu-Ni alloy) to reduce the cross-sectional area of ​​the metal part as a superconducting wire for PCS different from the superconducting magnet. Since these methods are countermeasures that have to be balanced with stabilization, they usually use methods such as placing the PCS in a place with a relatively low magnetic field and increasing the cross-sectional area of ​​the superconducting material to obtain a large load margin and thereby ensure stability. In addition, for the metal in contact with the superconducting material, a metal that does not hinder the raw material of the superconducting material from reacting to become a superconducting material during the processing of the superconducting wire is selected. According to these methods, the superconducting magnet and the PCS form a closed circuit that is superconductingly connected to each other at their two ends.

[0029] In a superconducting magnet operating in a constant current mode, it is desirable to connect the superconducting magnet and the PCS in a superconducting manner, give the PCS a desired resistance value when conducting normally, and realize an economical structure as a whole of the circuit of the superconducting magnet and the PCS. On the other hand, in a structure to which the contents of Patent Document 1 are applied, a portion of the superconducting wire that will become a ring is wound in such a way that the flowing current is in the same direction to form a superconducting magnet, and the PCS is formed by making the other portion a non-inductive coil. According to such a structure, it is no longer necessary to provide a superconducting connection between the superconducting magnet and the PCS, or the superconducting connection can be provided in one place.

[0030] Generally, superconducting connections require high technology, and the handling and workability of superconducting magnets in the application equipment must be ensured, so it is more economical than the previous structure that required two places for superconducting connections. On the other hand, since the superconducting wire magnet and PCS are composed of the same superconducting wire, the length of wire required for PCS will increase.

[0031] Therefore, the preferred embodiment described below aims to realize a small and light PCS compared to a PCS in which the superconducting connection between the superconducting magnet and the PCS is set at one point and the superconducting wire used for the PCS has the same structure as the superconducting wire of the superconducting magnet, thereby realizing a superconducting magnet economically.

[0032] [First embodiment]

[0033] Figure 1 This is a schematic circuit diagram of superconducting magnet 100 according to the preferred first embodiment.

[0034] exist Figure 1 In the embodiment, superconducting magnet 100 includes PCS 30 (current switch), first superconducting wire 50 (superconducting wire), second superconducting wire 52, excitation power supply 15 (DC power supply), and switch 16. Magnet portion 1 is formed by winding first superconducting wire 50 into a coil.

[0035] The excitation power supply 15 is a DC power supply, which is connected to the starting end 11 and the terminal 12 of the magnet part 1 via the switch 16 and the wire 14. In addition, the connection between the wire 14 and the first superconducting wire 50 can be a common solder connection. Thus, when the excitation power supply 15 is turned on by the switch 16, current is supplied between the starting end 11 and the terminal 12 of the magnet part 1.

[0036] PCS30 is generally referred to as a constant current switch, and includes a heating unit 20 for heating the second superconducting wire 52, and a power supply device 21 for supplying current to the heating unit 20. According to this embodiment, the starting end 11 and the terminal end 12 of the magnet unit 1 directly become the starting end and the terminal end of PCS30, and the magnet unit 1 and PCS30 are continuously connected through the first superconducting wire 50.

[0037] Figure 2 yes Figure 1 II-II cross-sectional view of the first superconducting wire 50 in FIG.

[0038] exist Figure 2 The first superconducting wire 50 includes a superconducting material portion 5, a low-resistance conductor layer 6, and a high-resistance conductor layer 7. The low-resistance conductor layer 6 is formed by forming Cu or a Cu-based alloy into a cylindrical shape. The high-resistance conductor layer 7 is arranged on the inner circumference side of the low-resistance conductor layer 6, and is formed by forming Fe or a Fe-based alloy into a cylindrical shape. In addition, the superconducting material portion 5 has MgB2 (magnesium diboride) as a main component and is arranged on the inner circumference side of the high-resistance conductor layer 7. However, a part of the superconducting material portion 5 may also contain substances other than superconducting materials.

[0039] Figure 3 yes Figure 1 FIG. 5 is a cross-sectional view taken along the line III-III of the second superconducting wire 52. FIG.

[0040] exist Figure 3 In the embodiment, the second superconducting wire 52 is formed from the first superconducting wire 50 (see Figure 2 ) is obtained by removing the low-resistance conductor layer 6. That is, the second superconducting wire 52 includes the high-resistance conductor layer 7 and the superconducting material portion 5. In addition, in the second superconducting wire 52, the low-resistance conductor layer 6 does not necessarily need to be completely removed, and the low-resistance conductor layer 6 may be processed to be thinner than the first superconducting wire 50, and the low-resistance conductor layer 6 may be left.

[0041] As described above, according to the present embodiment, the second superconducting wire 52 can be formed by removing all or part of the low-resistance conductor layer 6 from the first superconducting wire 50. Thus, the PCS 30 can be formed in a small size and at a low cost.

[0042] When the first superconducting wire 50 is applied to a MgB2 superconducting wire having a diameter of about 1.6 mm, for example, the superconducting material portion 5 only needs to contain 25% (weight percentage, the same below) or more of MgB2. In addition, the high-resistance conductor layer 7 only needs to contain 35% or more of Fe and 15% or more of SUS316L. In addition, the low-resistance conductor layer 6 only needs to contain 25% or more of Cu.

[0043] According to the structure of the first superconducting wire 50, the resistance per unit length can be set to 1×10 -3 Ω / m order. In the second superconducting wire 52 obtained by removing the low-resistance conductor layer 6 from the first superconducting wire 50, the resistance value per unit length can be set to 1×10 -2 Therefore, when the second superconducting wire 52 is applied to the PCS 30, the wire length in the PCS 30 can be shortened to about one tenth compared to the case where the first superconducting wire 50 is directly applied to the PCS 30.

[0044] Here, when the resistance value per unit length of the low-resistance conductor layer 6 is set to R6 (not shown) and the resistance value per unit length of the high-resistance conductor layer 7 is set to R7 (not shown), the ratio R7 / R6 is preferably greater than or equal to "2" and less than "10". 12 The reason is that if the ratio R7 / R6 is less than "2", the effect of "shortening the wire length in PCS30" will be insufficient. If the ratio R7 / R6 becomes "10", 12 If the ratio R7 / R6 is set to "10", the operation of the superconducting magnet 100 will become unstable. 7 The reason is that since the high-resistance conductor layer 7 can be realized with a cheaply available material, the cost of the superconducting magnet 100 can be reduced.

[0045] If the first superconducting wire 50 having the above structure is immersed in concentrated nitric acid, the low-resistance conductor layer 6 mainly composed of Cu will dissolve. On the other hand, the high-resistance conductor layer 7 mainly composed of Fe will hardly dissolve because it is in a passive state with respect to concentrated nitric acid. That is, if a part of the first superconducting wire 50 is immersed in concentrated nitric acid, the immersed part will be transformed into the second superconducting wire 52. However, the method of removing the low-resistance conductor layer 6 does not necessarily have to be a chemical method, and the low-resistance conductor layer 6 can also be removed by mechanical cutting.

[0046] Return to Figure 1The superconducting connection part 3 is a part that maintains the same characteristics as the first superconducting wire 50 and connects the ends of the first superconducting wire 50 to each other. As described above, according to this embodiment, the starting end 11 and the terminal end 12 of the magnet part 1 directly become the starting end and the terminal end of the PCS 30, and the magnet part 1 and the PCS 30 are continuously formed. Therefore, the required superconducting connection part 3 only needs to be one place as shown in the figure.

[0047] Here, the method for manufacturing superconducting magnet 100 is summarized as follows: Among these steps S1, S2, and S3, the execution order of steps S2 and S3 may be reversed.

[0048] Step S1 : Winding the first superconducting wire 50 to form the magnetic body portion 1 .

[0049] Step S2: In a predetermined portion of the first superconducting wire 50 excluding the magnetic body portion 1 , the low-resistance conductor layer 6 is removed (or the low-resistance conductor layer 6 is processed to be thin) to form the second superconducting wire 52 .

[0050] Step S3: Both ends of the assembly of the first superconducting wire 50 and the second superconducting wire 52 are joined together to form the assembly into a ring shape.

[0051] When the constant current mode is operated in the above structure, the magnet part 1 and the PCS 30 are in a normal conductive state, and the switch 16 is turned on to pass the excitation current to the magnet part 1. Then, the magnet part 1 and the PCS 30 are cooled to become a superconducting state, and the switch 16 is turned off when the excitation current reaches a desired value. Thus, the current continues to circulate between the magnet part 1 and the PCS 30.

[0052] Then, when the magnet part 1 is demagnetized, the power supply device 21 supplies current to the heating part 20. Thus, the heating part 20 heats the second superconducting wire 52 and makes it transition to the normal conductive state. Therefore, the current circulating in the magnet part 1 and the PCS 30 becomes zero.

[0053] [Second embodiment]

[0054] Figure 4 This is a schematic circuit diagram of a superconducting magnet 102 according to a preferred second embodiment. In the following description, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals and description thereof may be omitted.

[0055] exist Figure 4 In the embodiment, superconducting magnet 102 includes bobbin 10, PCS 31 (current switch), first superconducting wire 50, and second superconducting wire 52. Magnet portion 1 is formed by winding first superconducting wire 50 around bobbin 10.

[0056] In addition, although Figure 4 Although not shown in the figure, in this embodiment, between the starting end 11 and the terminal end 12 of the magnet portion 1, the structure of the first embodiment (see Figure 1 ) Similarly, the excitation power supply 15 is connected to a switch 16 and a conductor 14. The starting end 11 and the terminal end 12 of the magnet portion 1 directly become the starting end and the terminal end of the PCS 31, and the magnet portion 1 and the PCS 31 are continuously formed. The PCS 31 in this embodiment has a heater 8 for heating the second superconducting wire 52, and a heater power supply 9 for passing current to the heater 8.

[0057] The heater 8 is a device that passes current through a high-resistance metal (e.g., Cu-Ni) to generate heat. In the PCS 31, the second superconducting wire 52 is arranged in a straight line. When the second superconducting wire 52 is short, Figure 2 As shown, the second superconducting wire 52 only needs to be arranged in a straight line. However, in the case where a certain degree of length is required as the second superconducting wire 52, in order to save space, it is preferred to coil or bend the second superconducting wire 52. For example, a bobbin or a jig (not shown) for PCS31 may be arranged at a position different from the bobbin 10 of the magnet portion 1, and the second superconducting wire 52 may be wound thereon. In this case, it is preferred to arrange the second superconducting wire 52 in a manner that reduces inductance. Refer to Figure 5 and Figure 6 , illustrating the example.

[0058] Figure 5 and Figure 6 It is a diagram showing another arrangement method of the second superconducting wire 52 in the PCS 31.

[0059] exist Figure 5 In the embodiment, the second superconducting wire 52 is composed of a non-inductive coil. Figure 6 In the embodiment, the second superconducting wire 52 is arranged in a meandering shape. Figure 5 and Figure 6 In any of the configuration methods, the inductance in the second superconducting wire 52 can be reduced.

[0060] According to the present embodiment, similarly to the above-mentioned first embodiment, the superconducting connection portion 3 only needs to be provided at one location, and the PCS 31 can be configured in a compact and inexpensive manner.

[0061] [Third Embodiment]

[0062] Figure 7 This is a cross-sectional view of a main part of superconducting magnet 104 according to a preferred third embodiment. In the following description, parts corresponding to parts of other embodiments described above are denoted by the same reference numerals and description thereof may be omitted.

[0063] exist Figure 7 In the embodiment, the superconducting magnet 104 includes a bobbin 10, a PCS 31, a first superconducting wire 50, and a second superconducting wire 52. Although not shown in the figure, the superconducting magnet 104 includes an excitation power supply 15 (see FIG. 1 ) similarly to the superconducting magnet 100 of the first embodiment. Figure 1 ) and switch 16 (refer to Figure 1 ).

[0064] In this embodiment, the first superconducting wire 50 is wound around the bobbin 10, thereby forming the magnet part 1. In addition, the PCS 31 includes the second superconducting wire 52 and the heater 8. However, in this embodiment, the PCS 31 and the magnet part 1 are arranged close to each other, and the heat insulating layer 19 is inserted between the two. In addition, the structure and operation of the superconducting magnet 104 other than the above are similar to those of the superconducting magnet 102 of the second embodiment (see Figure 4 ) has the same structure and operation. As described above, according to the present embodiment, since the magnet unit 1 and the PCS 31 can be arranged close to each other, there is an advantage that the superconducting magnet 104 can be miniaturized.

[0065] [Fourth embodiment]

[0066] Figure 8 This is a schematic circuit diagram of a superconducting magnet 106 according to a preferred fourth embodiment. In the following description, portions corresponding to those of the other embodiments described above are denoted by the same reference numerals and description thereof may be omitted.

[0067] exist Figure 8 In the embodiment, the superconducting magnet 106 includes a PCS 32 (current switch), a first superconducting wire 70 (superconducting wire), a second superconducting wire 72, an excitation power supply 15, and a switch 16. The first superconducting wire 70 is wound into a coil shape to form a magnet portion 71. The functions of the excitation power supply 15 and the switch 16 are similar to those of the first embodiment (see Figure 1 )same.

[0068] Fig. 9 yes Figure 8 IX-IX cross-sectional view of the first superconducting wire 70 in FIG.

[0069] exist Fig. 9 In the embodiment, the first superconducting wire 70 includes a superconducting material portion 75, a low-resistance conductor layer 76, and a high-resistance conductor layer 77 which are stacked in sequence. They are all formed into a strip shape with a rectangular cross section, but their materials are different from those of the first embodiment (see Figure 2 ) are made of the same material as the superconducting material portion 5, the low-resistance conductor layer 6 and the high-resistance conductor layer 7.

[0070] Fig.10 yes Figure 8XX cross-sectional view of the second superconducting wire 72 in FIG.

[0071] The second superconducting wire 72 is obtained by removing the low-resistance conductor layer 76 from the first superconducting wire 70. That is, the second superconducting wire 72 includes a superconducting material portion 75 and a high-resistance conductor layer 77. As in the first embodiment, in the second superconducting wire 72, the low-resistance conductor layer 76 does not necessarily have to be completely removed, and the low-resistance conductor layer 76 may be made thinner than the first superconducting wire 70 and the low-resistance conductor layer 76 may be left. In addition, a plurality of first superconducting wires 70 or second superconducting wires 72 may be bundled into parallel conductors to form the magnetic body portion 71 or the PCS 32.

[0072] As described above, according to the present embodiment, the second superconducting wire 72 can be formed by removing all or part of the low-resistance conductor layer 76 from the first superconducting wire 70. Thus, the PCS 32 can be formed compactly and inexpensively, similarly to the first embodiment. Figure 1 to Figure 3 ) have the same structure and action.

[0073] [Fifth embodiment]

[0074] Fig.11 This is a schematic circuit diagram of a superconducting magnet 108 according to a preferred fifth embodiment. In the following description, portions corresponding to those of the other embodiments described above are denoted by the same reference numerals and description thereof may be omitted.

[0075] exist Fig.11 In the embodiment, the superconducting magnet 108 is different from the superconducting magnet 102 of the second embodiment (see Figure 4 ) is different from the superconducting magnet 108 in that PCS 34 is used instead of PCS 31. In other respects, superconducting magnet 108 is configured similarly to superconducting magnet 102. Therefore, the structures of first superconducting wire 50 and second superconducting wire 52 are also similar to those of superconducting magnet 102. Figure 2 and Figure 3 The structures of the superconducting wires shown are the same.

[0076] In addition, Figure 7 Similarly to the example shown in FIG. 1 , the PCS 34 may be provided by inserting a heat insulating layer 19 between the magnet part 1 and the PCS 34. The PCS 34 includes a second superconducting wire 52 and an AC power source 17. The AC power source 17 and the high-resistance conductor layer 7 (see FIG. 1 ) of the second superconducting wire 52 are connected to each other. Figure 3 )connect.

[0077] In the above structure, the operation in the case of constant current mode operation is the same as that in the first embodiment. On the other hand, when the magnet part 1 is demagnetized, the AC power supply 17 applies a predetermined AC voltage to the second superconducting wire 52. Since the inductance of the magnet part 1 is sufficiently larger than the inductance of the second superconducting wire 52, most of the current supplied from the AC power supply 17 flows into the second superconducting wire 72. As a result, the second superconducting wire 72 functions as a heater, and the second superconducting wire 52 is transferred to the normal conductive state, and the current circulating in the magnet part 1 and the PCS 34 becomes zero.

[0078] As a specific example, the high-resistance conductor layer 7 (see Figure 3 ) is a Fe-based alloy with a resistivity of 1.5×10 -2 [μΩm], the frequency of the AC voltage is 1MHz. In this case, the skin depth becomes 6×10 -2 [mm], most of the current flowing into the second superconducting wire 52 can flow into the high-resistance conductor layer 7.

[0079] [Sixth embodiment]

[0080] Fig.12 This is a schematic circuit diagram of a superconducting magnet 110 according to a preferred sixth embodiment. In the following description, portions corresponding to those of the other embodiments described above are denoted by the same reference numerals and description thereof may be omitted.

[0081] exist Fig.11 In the embodiment, the superconducting magnet 108 is different from the superconducting magnet 102 of the second embodiment (see Figure 4 ) is different from the superconducting magnet 110 in that the PCS 36 is used instead of the PCS 31. In other respects, the superconducting magnet 110 is configured similarly to the superconducting magnet 102.

[0082] The PCS 36 includes the second superconducting wire 52 , the electromagnet 18 (AC magnetic field generating unit), and the AC power source 17 . The electromagnet 18 is disposed at a position close to the second superconducting wire 52 .

[0083] In the above structure, the operation in the constant current mode is the same as that in the first embodiment. On the other hand, when the magnet part 1 is demagnetized, the AC power supply 17 applies a predetermined AC voltage to the electromagnet 18. Then, the high resistance conductor layer 7 (refer to Figure 3 ) generates an alternating magnetic field, generating eddy current in the high-resistance conductor layer 7. As a result, the high-resistance conductor layer 7 heats up, causing the second superconducting wire 52 to transition to a normal conductive state, and the current circulating in the magnet part 1 and PCS 34 becomes zero. Figure 3) has the effect of reducing the critical current, so this effect can also be used for the normal-conducting transition of the second superconducting wire 52.

[0084] [Effects of Embodiment]

[0085] According to the preferred embodiment as described above, the superconducting magnets 100 to 110 include: a magnet portion 1, 71, which is wound with a first superconducting wire 50, 70, and the first superconducting wire 50, 70 has a superconducting material portion 5, 75, a high-resistance conductor layer 7, 77 and a low-resistance conductor layer 6, 76 whose resistance per unit length is lower than that of the high-resistance conductor layer 7, 77; and a current switch 30 to 36, which includes a second superconducting wire 52, 72, the second superconducting wire 52, 72 has a superconducting material portion 5, 75 and a high-resistance conductor layer 7, 77, the second superconducting wire 52, 72 does not contain a low-resistance conductor layer 6, 76, or has a low-resistance conductor layer 6, 76 that is thinner than the low-resistance conductor layer 6, 76 in the first superconducting wire 50, 70. Thus, second superconducting wires 52 and 72 can be formed by removing low-resistance conductor layers 6 and 76 from first superconducting wires 50 and 70 , and superconducting magnets 100 to 110 can be formed at low cost.

[0086] Furthermore, it is more preferable that the current switch 31 includes a heater 8 for heating the second superconducting wire 52. Thus, when the magnet portion 1 is demagnetized, the second superconducting wire 52 can be transferred to the normal conducting state by the heater 8.

[0087] Furthermore, it is more preferable that the current switch 34 includes an AC power source 17 for applying an AC voltage to the high resistance conductor layer 7 of the second superconducting wire 52. Thus, current flows to the high resistance conductor layer 7, which generates heat, and the second superconducting wire 52 can be switched to a normal conduction state.

[0088] Furthermore, it is more preferable that the current switch 36 has an AC magnetic field generating unit 18 that generates an AC magnetic field to generate an eddy current in the high resistance conductor layer 7 of the second superconducting wire 52. Thus, the high resistance conductor layer 7 generates heat due to the eddy current, and the second superconducting wire 52 can be transferred to the normal conducting state.

[0089] In addition, it is preferable that the superconducting material portion 5, 75 contains MgB 2. Thereby, the superconducting material portion 5, 75 having a relatively high transition temperature can be manufactured at low cost.

[0090] In addition, it is more preferred that the low-resistance conductor layer 6 is formed by forming Cu or a Cu-based alloy into a cylindrical shape, and the high-resistance conductor layer 7 is arranged on the inner peripheral side of the low-resistance conductor layer 6, and the low-resistance conductor layer 6 is formed by forming Fe or a Fe-based alloy into a cylindrical shape, and the superconducting material portion 5 is arranged on the inner peripheral side of the high-resistance conductor layer 7. Thus, the low-resistance conductor layer 6 can be arranged at the outermost periphery, and the low-resistance conductor layer 6 can be easily removed when the second superconducting wire 52 is formed.

[0091] In addition, it is more preferable that superconducting magnets 100 to 110 further include: a DC power supply 15 for supplying current to first superconducting wire 50; and a switch 16 inserted between DC power supply 15 and first superconducting wire 50. Thus, current can circulate between magnet unit 1 and PCS 30 via switch 16 and DC power supply 15.

[0092] In addition, it is more preferable that the resistance value per unit length of the high-resistance conductor layer 7, 77 is at least twice and less than 10 times the resistance value per unit length of the low-resistance conductor layer 6, 76. 12 As a result, the operation of superconducting magnets 100 to 110 can be stabilized and the wire length of second superconducting wires 52 and 72 in current switches 30 to 36 can be sufficiently shortened.

[0093] Furthermore, it is more preferable that the low-resistance conductor layers 6 and 76 have a property of being dissolved by a predetermined treatment agent, and the high-resistance conductor layers 7 and 77 have a property of not being dissolved by the treatment agent or being less soluble than the low-resistance conductor layers 6 and 76. Thus, the low-resistance conductor layers 6 and 76 can be removed from the first superconducting wires 50 and 70 by the treatment agent to easily form the second superconducting wires 52 and 72.

[0094] [Modifications]

[0095] The present invention is not limited to the above-mentioned embodiments, and various modifications are possible. The above-mentioned embodiments are exemplified in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to having all the structures described. In addition, a part of the structure of a certain embodiment can be replaced with the structure of other embodiments, and the structure of other embodiments can be added to the structure of a certain embodiment. In addition, a part of the structure of each embodiment can be deleted or other structures can be added or replaced. In addition, the control lines and information lines shown in the figures show the control lines and information lines that are considered to be necessary for the description, and do not necessarily show all the control lines and information lines required in the product. It can be considered that almost all the structures are actually connected to each other. The modifications that can be made to the above-mentioned embodiments are, for example, as follows.

[0096] (1) In the above embodiments, the low-resistance conductor layers 6 and 76 have the property of being dissolved by a predetermined treatment agent (i.e., concentrated nitric acid), and the high-resistance conductor layers 7 and 77 have the property of not being dissolved in the treatment agent (or at least being less soluble than the low-resistance conductor layers 6 and 76). There are many combinations of low-resistance conductor layers 6 and 76, high-resistance conductor layers 7 and 77, and treatment agents having such chemical properties, and therefore, they are not limited to the combinations described in the above embodiments.

[0097] (2) In the above-mentioned embodiments, examples in which the present invention is applied to a superconducting magnet are described. However, only the first superconducting wires 50 and 70 may be circulated.

[0098] Description of Reference Numerals

[0099] 1.71 Magnet part

[0100] 5.75 Superconducting Materials Department

[0101] 6.76 Low resistance conductor layer

[0102] 7, 77 High resistance conductor layer

[0103] 8 Heater

[0104] 15 Excitation power supply (DC power supply)

[0105] 16 Switch

[0106] 17 AC power supply

[0107] 18 Electromagnet (AC magnetic field generating unit)

[0108] 30~36PCS(current switch)

[0109] 50, 70 No. 1 superconducting wire (superconducting wire)

[0110] 52, 72 Second Superconducting Wire

[0111] 100~110 superconducting magnets.

Claims

1. A superconducting magnet, characterized in that: have: a magnetic body portion wound with a first superconducting wire having a superconducting material portion, a high-resistance conductor layer, and a low-resistance conductor layer having a lower resistance per unit length than the high-resistance conductor layer; as well as A current switch comprising a second superconducting wire having the superconducting material portion and the high-resistance conductor layer, The second superconducting wire does not include the low-resistance conductor layer, or has the low-resistance conductor layer formed thinner than the low-resistance conductor layer in the first superconducting wire. The second superconducting wire is formed by removing the low-resistance conductor layer or thinning the low-resistance conductor layer in a portion other than the magnetic portion of the first superconducting wire. The assembly of the first superconducting wire and the second superconducting wire is composed of a continuous superconducting wire, and both ends are connected by a superconducting connection portion, so that the assembly is formed into a ring shape. The resistance value per unit length of the high-resistance conductor layer is at least twice and less than 10 times the resistance value per unit length of the low-resistance conductor layer. 12 times.

2. The superconducting magnet according to claim 1, characterized in that The current switch includes a heater for heating the second superconducting wire.

3. The superconducting magnet according to claim 1, characterized in that The current switch includes an AC power source for applying an AC voltage to the high-resistance conductor layer of the second superconducting wire.

4. The superconducting magnet according to claim 1, characterized in that The current switch includes an AC magnetic field generating unit configured to generate an AC magnetic field to generate an eddy current in the high-resistance conductor layer of the second superconducting wire.

5. The superconducting magnet according to any one of claims 1 to 4, characterized in that The superconducting material portion contains MgB2.

6. The superconducting magnet according to claim 5, characterized in that The low-resistance conductor layer is formed by forming Cu or a Cu-based alloy into a cylindrical shape. The high-resistance conductor layer is arranged on the inner peripheral side of the low-resistance conductor layer, and is formed by forming Fe or Fe-based alloy into a cylindrical shape. The superconducting material portion is arranged on the inner peripheral side of the high-resistance conductor layer.

7. The superconducting magnet according to claim 1, characterized in that Also available: a DC power source for supplying electric current to the first superconducting wire; and A switch is inserted between the DC power supply and the first superconducting wire.

8. The superconducting magnet according to claim 1, characterized in that The low-resistance conductor layer has a property of being dissolved by concentrated nitric acid. The high-resistance conductor layer has a property of not being dissolved by the concentrated nitric acid or being less soluble than the low-resistance conductor layer.

9. A method for producing a superconducting magnet, characterized in that: The process is as follows: A process of winding a first superconducting wire to form a magnetic body portion, wherein the first superconducting wire has a superconducting material portion, a high-resistance conductor layer, and a low-resistance conductor layer having a lower resistance per unit length than the high-resistance conductor layer; A process of removing the low-resistance conductor layer or thinning the low-resistance conductor layer in a portion other than the magnetic portion of the first superconducting wire to form a second superconducting wire; and A process of forming a collection of the first superconducting wire and the second superconducting wire into a ring shape by joining both ends of the collection of the first superconducting wire and the second superconducting wire at one superconducting connection portion, wherein the collection is composed of a continuous superconducting wire, The resistance value per unit length of the high-resistance conductor layer is at least twice and less than 10 times the resistance value per unit length of the low-resistance conductor layer. 12 times.

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