JPS6221244B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a superconducting magnet in which a compound superconductor is formed by performing a diffusion heat treatment after winding, and in particular, it is intended to strengthen the coil. Conventionally, this type of superconducting magnet has been manufactured by winding a composite wire 2, which forms a compound superconductor through a diffusion reaction, around a winding frame 1, for example, a stainless steel bobbin, as a solenoid winding, as shown in FIG. A reinforcing wire 3 such as a Cypronickel wire is wound in several layers and then heat treated at a high temperature to form a compound superconductor. The reinforcing wires 3 are arranged in such a manner that round wires or square wires are wound in alignment as shown in FIG. 1b. The above-mentioned reinforcing wire has high diffusion tension at room temperature or low temperature, but once exposed to high temperature, it softens and its expansion force decreases to about 1/3. Therefore, it was not possible to fully demonstrate its function as a reinforcing wire. Furthermore, since the reinforcing wire is made of metal wire, its coefficient of linear expansion is larger than that of a compound superconductor formed by diffusion heat treatment, so the amount of shrinkage will inevitably increase, causing local compressive stress due to loosening and shrinkage strain in the winding. In addition, the winding of the compound superconducting wire may become loose or may be damaged. The present invention has been made as a result of extensive research aimed at improving these drawbacks, and as a result has discovered a superconducting magnet made of a winding wire that has high strength and excellent thermal conductivity. That is, the present invention relates to a superconducting magnet in which a compound superconductor is formed by diffusion heat treatment after winding, in which at least the outermost layer of the winding is a non-magnetic metal matrix in which non-superconducting compound fibers are discontinuously dispersed. It is characterized by being made of a metal composite. One example of the present invention will be explained based on the drawings. As shown in FIG. A non-magnetic metal composite wire 4 whose outermost layer is a non-magnetic metal matrix in which non-superconducting compound fibers (compound fibers that do not exhibit superconducting properties) are discontinuously dispersed.
After forming the superconductor at a high temperature, it is heat-treated at a high temperature to simultaneously form a compound superconductor and a non-superconducting compound. Although the above-mentioned nonmagnetic metal composite wire is necessarily provided in the outermost layer of the winding, it may be provided in an intermediate layer thereof, or the layer may be provided in one layer or in multiple layers. Further, in the present invention, the composite wire 4 is formed by winding a reinforcing wire 5 into a coil as shown in FIG.
A plurality of non-superconducting compounds 7 are built into the core. Note that the non-magnetic metal matrix is Cu,
Al, Ag, CuNi, CuSn, CuZn, stainless steel, etc. are used. Also, as a non-superconducting compound, Cu
- Various compounds such as Ti, Al-Ti, Ni-Ti, Al-Cu, and Cu-NbTi are used. The reinforcing wires 5 may be arranged in any arrangement other than that shown in FIG. 2b, as long as they can be wound in alignment, such as rectangular wires, tapes, and stranded wires. Next, examples of the present invention will be described. Example 1 A niobium 505 core is embedded in a CuSn alloy, and its outer periphery is covered with a Ta tube and an OFHC copper tube, with an outer diameter of 0.25.
A composite line of mmφ was obtained. This composite wire is twisted at a pitch of 10mm. Then, the above 12 composite lines x 500m are 0.25 x 0.75mm ²
Stranded wire is formed around a stainless steel strip of 0.68×
A composite strand of 1.21 was obtained. 30μ for such composite stranded wire
A 450 m conductor measuring 0.8 x 1.33 mm ² was obtained by taping two layers of mt x 5 mm ^w glass tape in the Z direction and S direction. Two solenoids with a drum diameter of 60φ, an outer diameter of 100φ, and a length of 150 mm were fabricated using this conductor, and one of the solenoids had an outer diameter of 0.3 mm with a 1:1 composite of copper and Ti-10%Nb alloy. The solenoid of the present invention was made by winding the composite wire in a four-layer arrangement. On the other hand, a conventional solenoid was made by winding 0.3 mmφ Cypronickel wire in a four-layer arrangement. These two solenoids were subjected to diffusion heat treatment at 650°C for 45 hours to form a Nb ₃ Sn compound superconductor. In addition, as a result of performing diffusion heat treatment on a short sample of the above conductor at 650℃ x 45 hours and measuring the critical current, it was found that the critical current was measured at 10T.
It was confirmed that it was within the range of 195±5A. The solenoid of the present invention and the conventional solenoid were each made of a NbTi alloy superconducting magnet (inner diameter 130 mm).
Table 1 shows the results of applying current by applying a 7T bias magnetic field (mmφ).

[Table] In addition, the strength, thermal contraction rate, and estimated thermal conductivity were measured for samples of copper, Ti-10% gold-containing wire, and Cypronickel wire arranged and wound on the outside of the superconducting solenoid and treated at 650℃ and 45 hours. death,
When compared with the characteristics of Nb ₃ Sn wire, the results shown in Table 2 below were obtained.

[Table] In other words, the actual measured values showed that the strength was about twice as high and the heat shrinkage rate was about 1/2.5. As is clear from the table above, it was confirmed that the solenoid of the present invention achieved a magnetic field of 10.1T, and the conventional solenoid achieved a magnetic field of 8.7T. Furthermore, in the solenoid of the present invention, almost no training was observed and a magnetic field could be generated stably, whereas in the conventional solenoid, the training was intense and the sound of the winding movement was detected every time it was excited, making it unstable. This is due to the fact that the reinforcing wire in conventional solenoids, the Cypronickel wire, softens at 650°C, reducing its strength and significantly inhibiting its function as a reinforcing material.In addition, in the process of cooling the Cypronickel to a low temperature, the thermal contraction is large and the compound This is thought to be due to the disordered arrangement of the superconducting windings. As detailed above, according to the present invention, the reinforcing wire used for reinforcing the coil has approximately three times the strength of annealed metal, and has the same thermal conductivity as ordinary metal wire. Indicated. Furthermore, the thermal shrinkage was not only about 1/3 that of ordinary metals, but also almost the same as that of compound superconducting wires, so no damage due to thermal contraction was observed. Therefore, it has remarkable effects such as forming a stable coil during heat treatment after winding.

[Brief explanation of the drawing]

Fig. 1 shows a conventional superconducting magnet, Fig. 1a is a schematic explanatory diagram thereof, Fig. 1b is an arrangement diagram of reinforcing wires in the conventional magnet, and Fig. 2 shows a superconducting magnet of the present invention. FIG. 2a is a schematic explanatory diagram thereof, and FIG. 2b is an arrangement diagram of reinforcing wires in the magnet of the present invention. DESCRIPTION OF SYMBOLS 1... Winding frame, 2... Composite wire, 3... Reinforced wire, 4... Non-magnetic metal composite wire, 5... Reinforced wire, 6... Non-magnetic matrix, 7... Non-superconducting compound.

Claims (1)

[Claims] 1. In a superconducting magnet in which a compound superconductor is formed by diffusion heat treatment after winding, at least the outermost layer of the winding is a non-magnetic metal composite in which non-superconducting compound fibers are discontinuously dispersed in a non-magnetic metal matrix. A superconducting magnet characterized by being formed in.