JPH05291034A - Superconducting magnet device - Google Patents

Abstract

PURPOSE:To manufacture a compact superconducting magnet device exhibiting excellent performances by a method wherein a superconductive coil is self-contained in a space adiabatically expanding the gas inside the cylinder of a heat regenerating refrigerator while an insulation sealed electrode is taken out so as to directly cool down the superconducting coil using the refrigerator actuating gas. CONSTITUTION:A superconducting coil 21 is self-contained inside a cylinder 26 reciprocating a displacer 25 containing a heat regenerating material 27. Besides, an electrode 23 for conduction is protrusively provided out of the semiconducting coil 21 passing through a part of the cylinder 26 to be led out of the cylinder 26 after it is electrically insulation-sealed. Furthermore, a magnetic field generating space 29 is allotted in the superconducting coil 21. On the other hand, an adiabatic expansion chamber 28 is located on the position held by the displacer 25 and the superconductive coil 21. Through these procedures, the title super conductive magnet device can function as a magnetic field generating device capable of stably sustaining the superconducting state for shorter initial cooling down time at lower attaining temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet device.

[0002]

2. Description of the Related Art FIG. 3 shows the principle of operation of a Gifford McMahon cycle (hereinafter referred to as GM cycle) which is the principle of the present invention. The GM cycle includes a cylinder S, a displacer D for moving the gas in the cylinder, a regenerator R for cooling and heating the gas through a medium, and an intake valve V ₁ and an exhaust valve for intake and exhaust of the gas. It is composed of a valve V ₂ and a compressor C that generates high-pressure gas. Exhaust valve V in (a) → (b)
₂ is closed and the intake valve V ₁ is opened to fill the room-temperature space W above the cylinder with high-pressure gas from the compressor. Then, when the displacer D is moved to the highest position while the intake valve V ₁ is open, the high pressure gas in the room temperature space W is cooled through the regenerator R and moved to the low temperature space E below the cylinder. In this process, a shortage of high pressure gas is replenished through the intake valve V ₁ . (b) →
In (a), the intake valve V ₁ is closed and the exhaust valve V ₂ is opened to release the high pressure gas in the low temperature space E. As a result, adiabatic expansion is performed and cold (low-temperature low-pressure gas) is generated. After absorbing the refrigeration load (LOAD), the cold cools the regenerator R and returns to the suction side of the compressor C. In (c) → (d), the displacer D is moved to the lowest position while the exhaust valve V ₂ is open. At this time, the cold of the low temperature space E cools the regenerator R (the gas itself is heated), moves to the room temperature space W, and partly returns to the compressor C. In (d) → (a), the exhaust valve is closed and the intake valve is opened to fill the room temperature space with high-pressure gas to complete one cycle.

The applicant of the present invention has previously proposed a method for cooling a superconducting magnet to a superconducting state by heating the superconducting magnet in a cold head of a cold storage helium refrigerator of such a highly reliable Giford-McMahon cycle system. A method of conducting and cooling by contact is disclosed ((Japanese Patent Application No. 3-104).
No. 042) hereinafter referred to as the prior invention). This is to cool the superconducting coil winding by conduction from the cold head through the coil winding frame and the electric insulating material, but it takes time for steady cooling, and heat generated by magnetic and mechanical disturbance generated in the superconducting coil. Takes a long time to remove, and there is a problem that it is necessary to have a sufficient margin with respect to the critical temperature of the superconducting coil in order to keep the superconducting state stable.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact superconducting magnet device having excellent performance by solving the above problems.

[0005]

A superconducting coil 2 is provided in a space 29 for adiabatic expansion of gas in a cylinder of a cold storage refrigerator.
1 is built in, and the electrode 23 is taken out through the insulating seal 24, whereby the superconducting coil 21 is directly cooled by the working gas of the refrigerator. The refrigerator 39 and the superconducting coil 30 are combined with the current lead 37, the heat shield plate 34, the vacuum container 36, the compressor 40, and the power source 42 to form a magnetic field generator.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to explaining the present invention, a cooling device for a superconducting coil according to the prior invention disclosed by the present applicant will be briefly described. In FIG. 4, the superconducting coil 1 is a coil formed by linearly winding a superconducting material such as a metal-based or oxide-based superconducting material, and is formed in a cylindrical shape having a through hole in the center. The lower end of the superconducting coil 1 is closely fixed to the second stage cooling stage 5 of the regenerator 4 by screwing or the like. The vacuum container 2 is made of a non-magnetic material such as stainless steel, and the superconducting coil 1 is encapsulated in vacuum. Thermal shield 3
It is made of a material having a high thermal conductivity such as thin copper, the superconducting coil 1 is directly included therein, and the end portion of the opening is brought into close contact with the first-stage cooling stage 6 and fixed by screwing or the like. .. The current lead 7 is connected to the superconducting coil 1 and supplies a current. The current lead 7 is externally connected to a protective resistor 8, a breaker 9, and a power supply 10. The regenerator 4 has a drive unit that is exposed to the outside of the vacuum container 2 and is connected to the flexible hose 1.
The compressor 12 is connected to the compressors 1 and 11. For example, the physical property measurement sample 13 is a superconducting substance, and a strong magnetic field is applied by the superconducting coil 1 to measure the critical magnetic field. The physical property measurement sample 13 is detachably fixed to the second stage cooling stage 5.

The inside of the vacuum container 2 is evacuated by a vacuum pump (not shown) to block heat conduction by air. Next, the regenerator 4 is operated to bring the second stage cooling stage 5 to an extremely low temperature to cool the superconducting coil 1 fixed to it. Also,
In order to prevent radiant heat from room temperature, the heat shield 3 is cooled by the first stage cooling stage 6. When a current is applied from the current lead 7, a strong magnetic field is generated from the superconducting coil 1.

[0008] Now, as in the previous invention utilizing the above-mentioned Gifford-McMahon cycle refrigerator, the cold head is cooled to a predetermined temperature by bringing the object to be cooled into thermal contact with the cold head of the regenerator. can do. Therefore, in the present invention, in order to enhance the cooling effect of the superconducting coil which is the object to be cooled, the inside of the cylinder 26 (the upper part of the figure) that reciprocates the displacer 25 containing the regenerator material 27 as shown in FIG. That is, the superconducting coil 21 is incorporated in the displacer at the lowest position). The superconducting coil 21 is formed by winding a superconducting wire around a coil winding frame 22. Depending on the case, the winding may be impregnated with epoxy resin after winding or the winding frame 22 may be removed. Further, an electrode 23 for energizing is installed from the superconducting coil 21 so as to penetrate a part of the cylinder 26, and electrically insulating seal 24.
The cylinder is pulled out to the outside. Further, a magnetic field generation space 29 is provided inside the superconducting coil 21.
28 is a gas adiabatic expansion chamber. This is a position sandwiched between the displacer 25 and the superconducting coil 21.

FIG. 2 shows a superconducting coil 3 having the structure shown in FIG.
0 built-in refrigerator 39, current lead 37, and heat shield plate 3
4, a vacuum container 36, a compressor 40, a gas pipe 41, an excitation power source 42 and the like are combined to provide a magnetic field utilization space 43. FIG. 2 shows an example of a two-stage type refrigerator, and any one-stage type, three-stage type or the like is possible. The current Li - as de, can be composed of a bismuth-based according to temperature conditions, the oxide superconductor such as yttrium-based, or metal-based superconductors _{(Nb 3 Sn, Nb 3 Al} , V 3 Ga , etc.). In FIG. 2, a low electrical resistance material such as copper is used for the current lead 3 from the terminal 38 to the first stage cooling stage 35.
7, an oxide current lead 32 of bismuth type or the like is used from the first cooling stage 35 to the electrode 31 of the superconducting coil 30. Also, the superconducting coil 30
Superconductive material of the metallic forming the (NbTi, Nb ₃ Sn, etc.),
Any oxide type or the like can be selected according to the temperature conditions.

As shown in the operating principle of the cold storage refrigerator, Gifoed McMahon cycle, shown in FIG. 3, the temperature is lowered by adiabatically expanding the gas as the disperser D integrated with the regenerator R moves. As a result, the temperature of the object to be cooled attached to the cold head portion can be lowered by the heat conduction of the solid through the cold head. Here, FIG.
As shown in (1), by incorporating a superconducting coil in a cylinder that adiabatically expands the gas, the gas can be directly cooled by the refrigerator cooling working gas. Step b of FIG. 3 →
In the adiabatic expansion process up to c, the temperature of the superconducting coil can be directly lowered by the working gas. By using the superconducting coil cooled in this way and kept in the superconducting state as the superconducting magnet device having the exciting current supply system shown in the embodiment of FIG. 2, the initial cooling time is short, the reached temperature is low, and the superconducting state is maintained. It can function as a magnetic field generator that can be stably maintained.

[0011]

【effect】

a) Since the gas is directly cooled, there is no contact heat resistance and the initial cooling time can be shortened and the ultimate temperature can be lowered. b) The heat generated by the magnetic and mechanical disturbance generated in the superconducting coil due to the excitation can be quickly removed. c) As a result, the margin for the critical current is increased, and the stability of the coil can be improved. Further, since it is possible to excite at a current density higher than that of conduction cooling, the coil can be made compact and the material cost of the device can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of the present invention.

FIG. 2 is likewise a second embodiment.

FIG. 3 is an explanatory diagram of the principle of the G / M cycle.

FIG. 4 is a sectional view of the prior invention.

[Explanation of symbols]

1 superconducting coil 2 vacuum container 3 heat shield 4 regenerative refrigerator 5 second stage cooling stage 6 first stage cooling stage 7 current lead 8 protective resistance 9 circuit breaker 10 power supply 11 flexible hose 12 Compressor 13 Sample for physical property measurement 21 Superconducting coil 22 Coil reel 23 Electrode 24 Insulation seal 25 Displacer 26 Cylinder 27 Regenerator 28 Adiabatic expansion chamber 29 Space 30 Superconducting coil 31 Electrode 32 Current lead 33 Second stage cooling stage 34 Heat shield plate 35 First stage cooling stage 36 Vacuum vessel 37 Current lead 38 Terminal 39 Refrigerator 40 Compressor 41 Gas pipe 42 Power supply 43 Space

Claims (2)

[Claims] 1. A superconducting coil (21) is built in a space (29) for adiabatically expanding a gas in a cylinder of a regenerator.
A superconducting magnet device characterized in that a superconducting coil (21) is directly cooled by a working gas of a refrigerator by taking out an electrode (23) through an insulating seal (24). 2. A refrigerator (39) and a superconducting coil (30) comprising a current lead (37), a heat shield plate (34), a vacuum container (36), and a compressor (4).
0), a superconducting magnet device characterized by being a magnetic field generating device by combining with a power source (42).