JPH118418A - Persistent current switch and superconducting electromagnet device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compact switch with small capacity and heat content by laminating a conductive path body, where cutting is performed for constituting a non-inductive circuit and a heater plate on a lamination plate where a superconductor and a stabilizing material are alternately laminated. SOLUTION: A plurality of superconductors, consisting of a plate-shaped NdTi alloy and a plurality of stabilizing materials consisting of a CuNi alloy, are laminated alternately so that the stabilizing material is set as the outermost layer and are rolled for forming a lamination plate. For consisting a non-inductive circuit on the lamination plate, laser-trimming machining is performed for forming a conductive path body 4, and insulation treatment is performed with a resin composition. A plurality of heater plates 5 are subjected to the insulation machining by performing similar fine machining on a manganese plate. Each conductive path pattern of the conductive path body 4 and the heater plate 5 is mutually turned reversed, a current input part 7 of the conductive path body 4 and an input part 8 of the heater plate 5 are provided, a laminated object 10 is adjusted to the curvature of a superconducting electromagnet, and flexural machining is performed for forming a switch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting electromagnet used for medical equipment, industrial equipment, scientific equipment, and the like, and more particularly to a permanent current switch suitable for use in a superconducting electromagnet.

[0002]

2. Description of the Related Art A superconducting electromagnet capable of obtaining a strong magnetic field as compared with a normal electromagnet apparatus in which a coil is wound around a ferromagnetic structure is used for physicochemical experiments, magnetic levitation, MRI, etc.
It plays an important role in various fields. When exciting with a constant current, a permanent current switch is incorporated into the superconducting magnet to form a superconducting magnet, both ends of the superconducting magnet (coil) are short-circuited with permanent current switches, and the superconducting magnet is disconnected from the excitation power supply. It is common to operate in current mode.

A thermal permanent current switch is a combination of a small coil composed of a superconducting wire embedded in a stabilizer and a heater. The superconducting wire is connected in parallel to a superconducting electromagnet, and is kept in a normal conducting state even in a cryogenic vessel (cryostat) by heating with a heater. When the permanent current switch is in the normal conduction state, power is supplied from the excitation power supply to the superconducting electromagnet, and when the superconducting electromagnet reaches a predetermined excitation state,
When the heater of the persistent current switch is turned off, the persistent current switch transitions to the superconducting state, and the superconducting electromagnet enters operation in the persistent current mode.

[0004] The coil used for the permanent current switch is non-inductively wound in order to suppress the effect of the magnetic field on the superconducting electromagnet. Further, the stabilizing material requires a relatively high electric resistance when power is supplied to the superconducting electromagnet, and therefore, a material such as a CuNi alloy having a relatively high resistivity and a high thermal conductivity is used. Also, in order to maintain stability during operation in the persistent current mode, a plurality of switches are connected in parallel and used.
In many cases, the current flowing through each permanent current switch is reduced.

Conventional permanent current switches include those using a solenoid-shaped coil and those using a spiral coil. FIG. 3 shows an example of a conventional permanent current switch using a spiral coil. FIG. 3A is a plan view of the permanent current switch, and FIG. 3B is a side view of the permanent current switch.

As shown in FIG. 3, a conventional permanent current switch has a groove 31 provided on a winding frame 3 made of a material having high heat conductivity.
In addition, a superconducting wire 1 is non-inductively wound, and at the same time, a heater wire 2 is embedded.

[0007]

SUMMARY OF THE INVENTION A permanent current switch is
It is necessary to immerse directly in liquid helium in order to make the superconducting transition prompt. Further, in order to prevent the quench of the permanent current switch, the place where the permanent current switch is installed in the cryostat is limited. That is, even if the liquid level of the liquid helium drops, the permanent current switch does not protrude from the liquid level of the liquid helium and needs to be installed in a place where the magnetic field is low.

[0008] When a plurality of permanent current switches are installed, the space required for installation is increased, and the capacity of a cryostat to be used must be increased. With the increase in the capacity of the cryostat, the consumption of liquid helium also increases, and the cooling cost, that is, the operating cost of the superconducting electromagnet device increases.

It is an object of the present invention to provide a small-sized permanent current switch having a small volume and a small heat capacity, and a superconducting electromagnet apparatus having a low operating cost.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a conductive path body formed by cutting a superconductor and a stabilizing material alternately to form a non-inductive circuit, and a heater plate. And a permanent current switch formed by stacking the following.

Further, the present invention is the above-mentioned permanent current switch, wherein the laminated board is composed of a plurality of superconductors and a stabilizing material which is one more than the number of the superconductors.

Further, the present invention is the above-described permanent current switch, wherein the heater plate is formed by cutting a plate-shaped resistor into a non-inductive circuit.

Further, the present invention is a superconducting electromagnet apparatus provided with the above-mentioned permanent current switch.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a plurality of plate-shaped superconductors made of an NbTi alloy and one more stabilizing material made of a CuNi alloy are combined so that the stabilizing material becomes the outermost layer.
The layers are alternately laminated to obtain a laminate.

Next, the laminate is subjected to rolling,
A thin laminate is obtained. Next, the laminate is cut by fine processing such as laser trimming to obtain a conductive path body. At this time, the adjacent conductive paths are cut so as to form patterns in which currents flow in opposite directions, thereby forming a non-inductive circuit.

A plate made of a resistance material such as manganin is subjected to similar fine processing to obtain a heater plate. Also at this time, adjacent conductive paths are cut so as to form a pattern in which current flows in opposite directions to form a non-inductive circuit. Make patterns with different positions.

The conductive path bodies and the heater plate obtained as described above are alternately laminated with an insulating film such as a polyimide film interposed therebetween. Further, the permanent current switch of the present invention can be obtained by applying resin impregnation and resin molding to a laminate of the conductive path body and the heater plate.

The permanent current switch of the present invention can be deformed according to the shape of the cryostat where the permanent current switch is installed, or according to the outer periphery of the superconducting electromagnet.

If a plurality of stacked conductive paths are connected in parallel, the same effect as when a plurality of permanent current switches are used can be obtained.

[0020]

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

FIG. 1 is an explanatory diagram showing the structure of the permanent current switch of the present invention. FIG. 2 is an explanatory diagram illustrating an example of a pattern of a conductive path body that forms a non-inductive circuit.

A superconductor composed of seven plate-shaped NbTi alloys and a stabilizing material composed of eight CuNi alloys are alternately laminated so that the stabilizing material is the outermost layer, and four superconductors are formed. A laminate was obtained. Next, this laminate was rolled to a width of 105
mm, a length of 500 mm and a thickness of 0.25 mm were obtained.

Next, as shown in FIG. 2 (the diagram is simplified for clarity), the laminate is subjected to laser trimming processing to form a non-inductive circuit, and the laminate is subjected to conductive trimming. Road 4 was obtained. Arrow 11 indicates the direction of current flow. The size of the conductive path is 100 mm x 10
0 mm x 0.25 mm, the width of the conductive path is 0.8 mm,
The cut width is 0.2mm and the total length of the conductive path is about 10m
(100 mm × 2 lines × 50 rows). In addition, since two conductive paths were obtained from one laminated plate, eight conductive paths 4 were obtained. Next, the conductive path body 4 was washed and subjected to an insulation treatment using a resin composition.

The same fine processing was performed on a manganin plate having a thickness of 0.3 mm to obtain eight heater plates 5. The heater plate 5 is also insulated.

Next, as shown in FIG. 1, the conductive path body 4 and the heater plate 5 are laminated with an insulating film 6 made of a polyimide resin having a thickness of 0.13 mm interposed therebetween to obtain a laminate 10. Was. Although FIG. 1 shows two conductive paths, eight conductive paths 4 are actually used. At this time, the conductive path pattern of the conductive path body 4 and the conductive path pattern of the heater plate are turned upside down so that the current input portion 7 of the conductive path body 4 and the input portion 8 of the heater plate 5 are turned over. Position was changed.

Further, the laminate 10 is bent in accordance with the curvature of the outer periphery of the superconducting electromagnet, is impregnated and solidified using a polymer resin composition, and is further subjected to a resin mold to obtain the permanent magnet of the present invention. A current switch was obtained (not shown). The thickness of the permanent current switch was 6.5 mm.

The permanent current switch of the present invention obtained as described above was used for an outer diameter of 180 mm, an inner diameter of 100 mm, and a height of 15 mm.
A superconducting electromagnet device of the present invention was obtained by incorporating the superconducting electromagnet of 0 mm and an inductance of 2.7 H into the outer periphery (not shown). At this time, the eight input units 7 were all connected in parallel.

As a comparative example, a conventional permanent current switch having a spiral coil was obtained by using a superconducting wire having an outer diameter of 0.8 mm in which an NbTi alloy was embedded in a copper alloy and a manganin wire having an outer diameter of 0.3 mm. Was. In order to provide the same performance as the permanent current switch of the above-described embodiment, a volume five times as large, a thickness of 15 mm and an outer diameter of 160 mm were required. The heat capacity was also large.

A superconducting electromagnet device incorporating the permanent current switch of the present invention was housed in a cryostat, cooled to extremely low temperature using liquid helium, and then operated in a 100 A permanent current mode to measure a time constant. The time constant of the permanent current switch of the present invention was 170 years.

When the time constant of the permanent current switch of the comparative example was measured in the same manner, the time constant was 168 years.

As described above, a small-sized, small-heat-capacity permanent current switch requiring only one-fifth the required volume of the conventional one is obtained.

Further, the cryostat housing the superconducting electromagnet of this embodiment can be made much smaller than the cryostat housing the superconducting electromagnet of the comparative example, so that the consumption of liquefied helium is small and the operating cost can be reduced. Was.

[0033]

According to the present invention, a small-sized permanent current switch having a small capacity and a small heat capacity, and a superconducting electromagnet apparatus having a low operating cost can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the structure of a permanent current switch according to the present invention.

FIG. 2 shows a pattern 1 of a conductive path body constituting a non-inductive circuit.
Explanatory drawing showing an example.

FIG. 3 is an explanatory diagram showing an example of a conventional permanent current switch using a spiral coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Superconducting wire 2 Heater wire 3 Reel 4 Conductor 5 Heater plate 6 Insulating film 7 Input part (for electric current of conductor) 8 Input part (for heater plate) 10 Laminate 11 Arrow 31 (provided on reel )groove

Claims (4)

[Claims] 1. A heater comprising: a conductive plate formed by cutting a superconductor and a stabilizing material alternately to form a non-inductive circuit; and a heater plate. Characterized permanent current switch. 2. The permanent current switch according to claim 1, wherein said laminated board is composed of a plurality of superconductors and one more stabilizing material than the number of said superconductors. 3. The permanent current switch according to claim 1, wherein the heater plate is formed by cutting a plate-shaped resistor into a non-inductive circuit. switch. 4. A superconducting electromagnet device comprising the permanent current switch according to claim 1.