JPH0399408A - Manufacture of superconducting magnet - Google Patents

Abstract

PURPOSE:To make it possible to manufacture a highly efficient small size superconducting magnet in which a quenching is hardly generated by a method wherein the inner layer of a coil is constituted using a completely stabilized superconducting wire material, the coil layer on the side outer than the above-mentioned layer is constituted by an incompletely stabilized superconducting wire material. CONSTITUTION:A superconducting coil is formed by winding a superconducting wire on a coil bobbin 1 as far as to the n-layer shown in the diagram. The first layer on the innermost layer side and the second layer are formed using a completely stabilized superconducting wire material 2. The third layer and upward layers are formed using an incompletely stabilized superconducting wire material 3. The electromagnetic force applied to the coil wire material when excitation is F2 at both end parts of the first layer. The electromagnetic force applied to the coil wire material in the vicinity of the center part of the first layer of the coil is shown by F1. The first and the second layers are especially affected substantially by the effect of the above-mentioned magnetic force, the wire material is slightly vibrated and slipped. However, the frictional heat by the above-mentioned slipping is absorbed and dispersed by the completely stabilized superconducting wire material with which the first and the second layers are formed, and the situation is brought under control without having a quenching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application) The present invention relates to a method of manufacturing a superconducting magnet that prevents quenching.

(Prior Art) Superconducting magnets made using superconducting wires can be made smaller and stronger than normal conducting magnets. However, in a superconducting magnet, the superconducting state of the superconducting wire that forms the coil may be broken, causing quenching.

One of the causes of quenching is the electromagnetic force that acts on the superconducting wire forming the superconducting magnet when the superconducting magnet is excited. Due to the action of this electromagnetic force, the superconducting wire forming the coil slips, generating frictional heat.

This frictional heat causes the temperature of the wire to rise, and when it exceeds a critical temperature, a portion of the superconducting wire changes from a superconducting state to a normal conducting state. In the normally conductive state, an electrical resistance value is generated and Joule heat is generated since the part is under current. Due to this heat generation, the area exceeding the critical temperature further increases, and finally the entire coil becomes a normal conduction state. If such a situation occurs, the coil may be damaged due to increased temperature or generation of high voltage.

Conventionally, in order to prevent quenching of superconducting wires, there are known stabilized superconducting wires.

FIGS. 3 and 4 show cross-sectional views of the stabilized superconducting wire. As shown in Figure 3, a stabilizing material such as oxygen-free copper 6
It is a wire rod in which a superconducting material 5 such as NbTi is embedded. The stabilizing material 6 used has excellent thermal conductivity and a large heat capacity.

Stabilizing wires can be broadly divided into two types based on the ratio of superconducting material to stabilizing material. The cross-sectional area of the superconducting material of the stabilizing wire is 5cus, and the cross-sectional area of the stabilizing material is Ss. The cross-sectional area ratio of stabilizing material/superconducting material: (Scu/SS) is a quantity related to the stability of the superconducting wire.

A superconducting wire with this ratio (Scu/Ss) of 7 or more is called a fully stabilized superconducting wire because it has high stability.

In the fully stabilized superconducting wire mentioned above, due to disturbance,
Even if a temperature rise occurs in a part of the wire, the heat capacity of the wire is larger than its calorific value, so the temperature rise will be small and the superconducting state will be maintained without exceeding the critical temperature, after which it will be cooled by a refrigerant and the initial temperature will be lowered. can be recovered to. Also,
In this case, it is possible to recover from the temporary state of normal conduction.

By forming the coil of a superconducting magnet using such superconducting wire, it is possible to create a superconducting magnet that is less likely to quench.

On the other hand, a superconducting wire having a stabilizing material/superconducting material cross-sectional area ratio (Scu/Ss) of 2 to 3, as shown in FIG. 4, is called an incompletely stabilized superconducting wire.

In superconducting magnets, the locations where the quench phenomenon occurs are:
This is where the electromagnetic force acts most strongly, that is, the innermost few layers of the coil. Conventionally, in order to prevent this quenching phenomenon, there is a method of forming superconducting magnet coils by a grading method. The grading method is a method of reducing the current density of the superconducting wire by increasing the cross-sectional area of the superconducting material in the superconducting wire forming the inner layer of the coil, on which a strong magnetic field acts. FIG. 5 shows an explanatory diagram of the grating method. The superconducting wire used for the outer layer of the coil is C wire, and the wire used for the inner layer of the coil is C wire and C wire. Although the diagram showing the wire is a schematic diagram of the cross section of the wire, it does not necessarily show the actual structure of the wire, but expresses the ratio of the superconducting material and the stabilizing material. The hatched area in the center of the circle indicates the cross-sectional area of the superconducting material: SCu, and the blank area around it indicates the cross-sectional area of the stabilizing material: SS. The cross-sectional area: Scu of the C wire and the superconducting material of the C wire is larger than SCu of the C wire. The difference between C wire and C wire lies in the cross-sectional area ratio of stabilizing material/superconducting material. C wire rod has ratio: (Scu
/Ss) is equal to the ratio of C wire: (Scu/Ss),
For C wire, the ratio: (Scu/Ss) is the ratio for C wire: (
Scu/Ss). The grating method uses C wire for the outer layer and B wire, C wire, or an intermediate wire for the inner layer.

(Problems to be Solved by the Invention) In the grating method described above, is it possible to determine whether the cross-sectional area ratio of the stabilizing material/superconducting material of the wire used in the inner layer is the same as that of the superconducting wire used in the outer layer? , or less, so it is insufficient in terms of resistance to quenching.

Furthermore, if a coil is formed using only the completely stabilized superconducting wire described above, the cross-sectional area of the superconducting material is smaller than the total cross-sectional area, so there is a drawback that the coil becomes large.

An object of the present invention is to prevent quenching and to obtain a novel method for manufacturing a small-sized superconducting magnet.

[Structure of the Invention (Means for Solving Problems) The grating method described above is a method of increasing the cross-sectional area of the superconducting material of the superconducting wire in the inner layer of the coil to lower the current density and prevent quenching. In contrast, in the method of the present invention, the superconducting wire forming the inner layer of the coil is made of a fully stabilized superconducting wire with a large heat capacity to prevent quenching, and the outer coil layer is made of an incompletely stabilized superconducting wire. It was designed to do so.

A superconducting wire with a small cross-sectional area ratio of stabilizing material/superconducting material has the disadvantage of being easily quenched, but it has the advantage of being able to be made smaller by manufacturing a coil. Superconducting wires with a large cross-sectional area ratio of stabilizing material/superconducting material are less likely to be quenched, but
The total cross-sectional area must be large, making the coil large. Therefore, as a result of careful consideration of the features of these wire rods and the locations where quenching occurs, we have arrived at the present invention.

A diagram schematically explaining the method of the present invention is shown in FIG. A wire used for the outer layer of the coil and B used for the inner layer of the coil
The difference between the wires is the cross-sectional area ratio of the stabilizing material/superconducting material. Similar to FIG. 5, the shaded area represents the superconducting material, and the surrounding blank area represents the stabilizing material. The a-wire is an incompletely stabilized superconducting wire, and the b-wire is a completely stabilized superconducting wire. As is clear from this figure, if the coil is formed only from B wire, it will become large.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a sectional view of the coil portion of the superconducting magnet of the present invention.

A superconducting coil is formed by winding n layers of superconducting wire around a coil winding frame 1. The first layer and the second layer on the innermost layer side are formed of completely stabilized superconducting wire 2. The third layer and higher layers are formed from the imperfect superconducting wire 3.

The electromagnetic force applied to the coil wire during excitation is a force F2 at both ends of the first layer, as shown in the figure. FIG. 2 shows the coil wire near the ta-th central part of the coil and the electromagnetic force F1 applied to the wire. The first and second layers are particularly strongly affected by these electromagnetic forces, causing the wire to move slightly and slip, but the frictional heat generated due to this is absorbed by the fully stabilized superconducting wire forming the 1st Ji11 2nd JiI. absorption,
It is dispersed and brought under control without reaching quench.

[Effects of the Invention] The production method of the present invention has the effect of making it possible to produce a compact, high-performance superconducting magnet that is resistant to quenching.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the coil of a superconducting magnet according to an embodiment of the present invention, Fig. 2 is an enlarged view of the coil portion, Fig. 3 is a cross-sectional view of a fully stabilized superconducting wire, and Fig. 4 is an incompletely stabilized superconducting wire. A sectional view of the wire rod, FIG. 6 is an explanatory view of the grating method, and FIG. 6 is an explanatory view of the wire rod used in the present invention. 1... Coil winding frame, 2... Completely stabilized superconducting wire,
3... Incompletely stabilized superconducting wire, 4... Superconducting wire, 5.7-... Superconducting material, 6.8... Stabilizing material Figure 1 Figure 2 Figure 4 Used in the outer layer of the coil Wire rods used for the outer layer of the coil Wire rod C wire used for the inner layer of the coil Wire rod used for the inner layer of the coil Figure 3

Claims (1)

[Claims] (1) In the production of superconducting magnets using superconducting wire,
A method for manufacturing a superconducting magnet, characterized in that the inner coil layer, which is subjected to the strong electromagnetic force of a superconducting coil, is made of a fully stabilized superconducting wire, and the outer coil layer is made of an imperfectly stabilized superconducting wire.