JPH09213519A - Superconducting magnet and superconductive wire material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a superconductive magnet formed so as to avoid causing the quench and superconductive wire material usable for windings of such superconductive magnet by blocking the superconductive wire material from moving in the actuation this magnet. SOLUTION: A superconductive magnet 3 is composed of so that the heat shrinkage amount of a superconductive wire material 2 with a temp. rise at the actuation of a superconductive magnet from the ambient temp. at reeling may be higher than that of a reel 1. The above-used wire material 2 has a higher heat shrinkage with a temp. rise at the actuation of the superconductive magnet from the ambient temp. at reeling than that of the reel 1.

Description

Detailed Description of the Invention

[0001]

The present invention relates to nuclear magnetic resonance (NM)
R) The present invention relates to a superconducting magnet used in an analyzer or the like and a superconducting wire used as a winding of the superconducting magnet, and particularly prevents the movement of the superconducting wire itself which is a constituent material of the superconducting magnet during excitation (operation). By doing so, the present invention relates to a superconducting magnet which prevents quenching and a superconducting wire useful as a winding wire for such a superconducting magnet.

[0002]

2. Description of the Related Art The superconducting phenomenon allows a large current to flow with zero resistance, and the use of this phenomenon is expanding in various fields such as large current transport and strong magnetic field generators. In particular, a superconducting magnet used in a high-resolution NMR analyzer or the like achieves a strong magnetic field by energizing a coil with a large current and a permanent current operation using zero resistance. This is a typical example of application technology that can be realized for the first time.

FIG. 1 is a sectional view showing the outline of the structure of a superconducting magnet. As shown in FIG. 1, the superconducting magnet 3 is configured by winding a superconducting wire 2 in a coil shape on a cylindrical winding frame 1 having flange portions at both ends.

In such a superconducting magnet, in order for the current to flow through the superconducting wire without resistance, it is limited to the case where the predetermined conditions are met. That is, at least three conditions are satisfied: (a) the flowing current is below the critical current, (b) the peripheral magnetic field is below the upper critical magnetic field, and (c) the ambient temperature is below the critical temperature. Need to be satisfied. If even one of these conditions is not satisfied, the superconducting wire falls into a high-resistance normal-conducting state for a while, and the expensive liquid helium as a refrigerant that keeps the superconducting wire below the critical temperature is evaporated in an instant, This causes a so-called quench that damages the superconducting wire itself.

The major cause of the above-mentioned quench is mechanical disturbance, and specifically, heat generated by the movement of the superconducting wire itself.
That is, when a portion of the superconducting wire moves to generate frictional heat, the ambient temperature rises and the critical current decreases, and the overflowed current flows through the non-superconducting portion and is accompanied by Joule heat generation. If the cooling is not sufficient, a vicious circle is formed and the ambient temperature exceeds the critical temperature, which causes the quench.

Therefore, in order to suppress the movement of the superconducting wire, the superconducting wire wound in a coil shape is generally hardened with an impregnating material, or a reinforcing material is provided outside the coil to support it. Has been. From this point of view, various methods for preventing the movement of the superconducting wire have been proposed so far. For example, in Japanese Unexamined Patent Publication No. 62-173705, a plurality of coils are provided and a material having a larger heat shrinkage amount than the winding portion of the inner coil is used for the winding frame of the outer coil.
A method of reinforcing the winding portion of the inner coil with the winding frame of the outer coil is disclosed.

[0007]

However, the conventional methods have the following problems. First, with the method of solidifying with an impregnating material, it is practically impossible to spread the impregnating material in all the gaps of the winding part, leaving the possibility that the superconducting wire of the winding part will move during the operation of the superconducting magnet. It cannot be a fundamental solution. Further, the method of providing and supporting the reinforcing material on the outside of the coil has a drawback in that it is substantially impossible to apply the tightening force applied to the reinforcing material to the entire superconducting wire material in which several layers are wound. Further, in the method disclosed in Japanese Patent Laid-Open No. 62-173705, the winding portion of the outermost coil is not reinforced, and the superconducting member of the winding portion still remains movable.

The present invention has been made in order to solve the technical problem in the prior art, and its purpose is to prevent the occurrence of quench by preventing the movement of the superconducting wire during the operation of the superconducting magnet. It is an object of the present invention to provide a superconducting magnet configured to do so, and a superconducting wire useful as a winding wire of such a superconducting magnet.

[0009]

The superconducting magnet of the present invention which can achieve the above object is a superconducting magnet constituted by winding a superconducting wire on a winding frame. The gist is that the heat shrinkage of the superconducting wire up to the operating temperature is larger than the heat shrinkage of the bobbin.

The superconducting wire of the present invention which can achieve the above object is a superconducting wire which is wound around a winding frame to form a superconducting magnet, and which varies from the ambient temperature during winding to the temperature during operation of the superconducting magnet. The heat shrinkage of superconducting wire up to
The gist is that it is higher than the heat shrinkage rate of the reel.

The above-mentioned superconducting wire of the present invention is specifically
Examples include a superconducting filament and a base material mainly composed of an Al alloy or an Ag alloy. The Nb-Ti alloy filament is most preferable as the superconducting filament of this superconducting wire.

As a material for the winding frame for winding the superconducting wire made of a base material mainly composed of the above Al alloy or Ag alloy, stainless steel can be cited, which is constituted by a combination of such a superconducting wire and the winding frame. Superconducting magnet
The effects of the present invention are maximized.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Stainless steel is generally used as a material for a winding frame which is a constituent member of a superconducting magnet. On the other hand, as the superconducting wire, Nb ₃ Sn or N
Generally, a large number of superconducting filaments such as b-Ti are embedded in a base material made of oxygen-free copper. In such a combination, the heat shrinkage of the superconducting wire from the winding temperature of the superconducting wire (usually room temperature) to the operating temperature of the superconducting magnet (usually liquid helium temperature) is less than that of the bobbin. It became smaller, and it was thought that the superconducting wire would move when the superconducting magnet was activated.

Therefore, based on the above relations, the present inventors have studied from various angles a structure capable of preventing the movement of the wound superconducting wire. As a result, if the superconducting magnet is constructed so that the amount of heat shrinkage of the superconducting wire from the temperature during winding to the temperature during operation of the superconducting magnet is greater than the amount of heat shrinkage of the bobbin, the above-mentioned object can be achieved successfully. I was found to be done. In addition, in order to configure such a superconducting magnet, the superconducting wire as its material is
The inventors have found that the heat shrinkage rate of the superconducting wire from the temperature during winding to the temperature during operation of the superconducting magnet should be higher than the heat shrinkage rate of the winding frame, and completed the present invention.

The superconducting magnet of the present invention is constructed as described above. In short, the superconducting magnet is cooled to, for example, liquid helium temperature by defining the relationship between the superconducting wire and the amount of heat shrinkage in the bobbin as described above. In doing so, the superconducting wire itself is made to function as a reinforcing material, so that the superconducting wire is fixed to the winding frame.
That is, according to such a configuration, when the superconducting wire is wound around the winding frame and then cooled from the temperature at the time of winding to the temperature at which the superconducting magnet operates, the amount of heat shrinkage of the superconducting wire is the amount of heat shrinkage of the bobbin. Therefore, the superconducting wire wound under tension is more firmly fixed to the bobbin to prevent the superconducting wire from moving. By doing so, the occurrence of quench in the superconducting magnet could be prevented.

As a specific example of the superconducting wire in the present invention, a superconducting filament and a base material mainly composed of an Al alloy or an Ag alloy can be mentioned. Like this
When a superconducting wire made of a base material mainly composed of an Al alloy or an Ag alloy is used, in relation to a stainless steel reel,
The requirements defined by the present invention are satisfied, and the effects of the present invention described above are achieved.

In the above, "(Al alloy or Ag
It is based on the following reason. That is, in the present invention, it is also effective to configure the base material with, for example, a double pipe, and when adopting such a configuration, the material forming the outermost layer portion of the base material is the Al alloy or Since the effect of the present invention can be achieved with an Ag alloy, in consideration of such a case, the "base material mainly containing an Al alloy or an Ag alloy" is used. From this point of view, the inner layer portion of the base material (that is, the portion in which the superconducting filament is embedded) is made of conventional Cu (or Cu alloy).
The outermost layer may be made of Al alloy or Ag alloy.

By the way, mainly Al alloys and Ag alloys are used.
When a base material is used, the superconducting filler embedded in it
Ment as Nb_Three It is possible to use Sn, but
Nb _Three Since the Sn superconducting filament is brittle, the amount of heat shrinkage
Nb in base material when stress from large base material is applied
_Three The Sn superconducting filament may be damaged.
You. Also, an oxide in which a sheath material is filled with an oxide superconducting material
This problem also occurs in the superconducting wire. this
Point, if it is Nb-Ti alloy filament, toughness is good
Therefore, even if some stress is applied, such inconvenience
Does not occur, so Al alloys and Ag alloys are mainly used
As a superconducting filament embedded in the base material
Are most preferably Nb-Ti alloy filaments.

A used as a base material of a superconducting wire in the present invention
The type of the l alloy or the Ag alloy is not particularly limited, and may be, for example, Al-Cu system, Al-Mg system, or Al.
-Si system, Al-Mn system, Al-Cu-Mg system, Al-
Al alloys such as Mg-Zn type and Al-Mg-Si type, and A
Various known alloys containing a predetermined amount of each alloy element, such as Ag alloys such as g-Cu-based, Ag-Mg-based, Ag-Zn-based, etc., can be used. Further, these alloys can be used in combination as in the double tube described above.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any change in the design of the present invention can be made without departing from the spirit of the preceding and the following. It is included in the technical scope.

[0021]

【Example】

Example 1 55 rods of Nb-Ti alloy having a diameter of 6 mm and a length of 200 mm were used, and an A of a diameter of 67 mm and a length of 200 mm was used.
It was embedded in a pre-drilled hole in a base material made of 1-Mg alloy, and aluminum lids were welded to both ends to obtain a composite billet. This composite billet was extruded at 400 ° C. at an extrusion ratio of 20, and then heat treatment and wire drawing were repeated to obtain an Nb—Ti alloy superconducting wire having a diameter of 1 mm. At this time, the heat treatment temperature was 400 ° C. and the heat treatment time was 12 hours, which was repeated four times in total.

The obtained Nb-Ti alloy superconducting wire was cooled from room temperature to 20K, the shrinkage was measured, and the shrinkage at liquid helium temperature was determined by extrapolation to be 0.31.
It was 9%. Further, the shrinkage ratio of SUS304 used as the reel material at the temperature of liquid helium was determined by the same method to be 0.306%.

The above Nb-Ti alloy superconducting wire was wound around a SUS304 reel at room temperature to produce a superconducting magnet. When this superconducting magnet was cooled to liquid helium temperature and subjected to an excitation test, it was possible to excite up to the rated operating current without quenching.

Example 2 55 rods made of Nb-Ti alloy having a diameter of 6 mm and a length of 200 mm, and an A having a diameter of 67 mm and a length of 200 mm.
It was embedded in a pre-drilled hole of a base material made of a g-Mg alloy, and Ag lids were welded to both ends to obtain a composite billet. This composite billet was extruded at 400 ° C. at an extrusion ratio of 20, and then heat treatment and wire drawing were repeated to obtain an Nb—Ti alloy superconducting wire having a diameter of 1 mm. At this time, the heat treatment temperature was 400 ° C. and the heat treatment time was 12 hours, which was repeated four times in total.

The shrinkage of the obtained Nb-Ti alloy superconducting wire was measured while cooling it from room temperature to 20K, and the shrinkage at liquid helium temperature was determined by extrapolation to be 0.31.
5%. Further, the shrinkage rate of SUS304 used as the reel material at the temperature of liquid helium was determined by the same method to be 0.306%.

The above Nb-Ti alloy superconducting wire was wound around a SUS304 reel at room temperature to produce a superconducting magnet. When this superconducting magnet was cooled to liquid helium temperature and subjected to an excitation test, it was possible to excite up to the rated operating current without quenching.

Comparative Example 1 55 Nb-Ti alloy rods having a diameter of 6 mm and a length of 200 mm were embedded in pre-drilled holes of a base material made of oxygen-free copper and having a diameter of 67 mm and a length of 200 mm at both ends. An oxygen-free copper lid was welded to form a composite billet. This composite billet was extruded at 400 ° C. at an extrusion ratio of 20, and then heat treatment and wire drawing were repeated to obtain an Nb—Ti alloy superconducting wire having a diameter of 1 mm. At this time, the heat treatment temperature was 400 ° C. and the heat treatment time was 12 hours, which was repeated four times in total.

The obtained Nb-Ti alloy superconducting wire was cooled from room temperature to 20K, the shrinkage was measured, and the shrinkage at liquid helium temperature was determined by extrapolation.
It was 65%. The shrinkage ratio of SUS304, which is a reel material, at the temperature of liquid helium is 0.3 in the same manner.
It was 06%.

The above Nb-Ti alloy superconducting wire was wound around a SUS304 reel at room temperature to produce a superconducting magnet. When this superconducting magnet was cooled to the temperature of liquid helium and subjected to an excitation test, it was found that quenching occurred when the superconducting magnet was energized to a current of 5/7 of the rated operating current and could not be excited normally.

[0030]

The present invention is configured as described above, and the amount of heat shrinkage of the superconducting wire from the ambient temperature during winding to the temperature during operation of the superconducting magnet is greater than that of the bobbin. With this structure, it is possible to prevent the movement of the superconducting wire and prevent the occurrence of quench in the superconducting magnet. In addition, a superconducting wire rod that can achieve these effects was realized.

[Brief description of drawings]

FIG. 1 is a sectional view showing an outline of a configuration of a superconducting magnet.

[Explanation of symbols]

 1 reel 2 superconducting wire 3 superconducting magnet

Claims (5)

[Claims] 1. In a superconducting magnet constructed by winding a superconducting wire on a winding frame, the amount of heat shrinkage of the superconducting wire from the ambient temperature during winding to the temperature during operation of the superconducting magnet is A superconducting magnet, which is configured to be larger than the quantity. 2. A superconducting wire which is wound around a winding frame to form a superconducting magnet, wherein the heat shrinkage rate of the superconducting wire from the ambient temperature during winding to the temperature during operation of the superconducting magnet is A superconducting wire which is characterized by having a shrinkage ratio greater than that of the superconducting wire. 3. A superconducting filament and a base material mainly containing an Al alloy or an Ag alloy.
The superconducting wire according to. 4. The superconducting filament is Nb-Ti.
The superconducting wire according to claim 3, which is an alloy filament. 5. A superconducting magnet, characterized in that the superconducting wire according to claim 3 or 4 is wound around a winding frame made of stainless steel.