JPH05175045A - Super conducting magnet - Google Patents

Abstract

PURPOSE:To reduce heat generation in an inner chamber of a supercon-ductiving magnet and a superconducting coil and eliminate the amount of evaporation of refrigerant by a method wherein a radiation shield is composed of a material having low electric conductivity, and a member having high heat conductivity is arranged in a part of the radiation shield, and a cooling pipe is provided in a member having high heat conductivity. CONSTITUTION:A radiation shield 1 is composed of a member 2 having low electric conductivity, and a member 3 having high heat conductivity is divided and arranged on this surface. Further, a cooling pipe 4 is connected to the member 3 having high heat conductivity and placed. Thus, an eddy current generated in the radiation shield is suppressed, and the amount of heat generation can be made less in a superconductive coil and an inner chamber, and also a temperature gradient in the radiation shield itself is suppressed, whereby an invaded heat by the radiation can be reduced and the amount of evaporation of the refrigerant can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet used under fluctuating magnetic flux.

[0002]

2. Description of the Related Art FIG. 2 is a perspective view of a conventional superconducting magnet for a magnetic levitation train. There is a superconducting coil (not shown) and an inner tank (not shown) that stores liquid helium for cooling the superconducting coil, and the radiation shield 1 covers the inner tank.
Are present and are cooled with vaporized helium or liquid nitrogen. Further, an outer tank (not shown) is provided on the outer peripheral side of the radiation shield 1.
There is. In addition, a rapid induction current is generated in the radiation shield 1 when the superconducting coil is quenched, and the radiation shield 1 buckles due to the electromagnetic force due to the interaction between the superconducting coil and the eddy current. In order to prevent this, the radiation shield 1 is composed of a member 2 having a high electric conductivity and a member 3 having a low electric conductivity, which are joined together by using a fastener 5 such as a rivet. By doing so, the flow path of the eddy current is limited to the member 1 having high electric conductivity, and a large electromagnetic force is not generated. For example, as an example of the structure of such a superconducting magnet, Japanese Patent Laid-Open No.
-95970 publication is mentioned.

[0003]

In the prior art, when the radiation shield resonates with a harmonic of a specific frequency from the ground coil under the direct current magnetic flux of the superconducting magnet for the magnetic levitation train, the outer tank and the radiation shield are oscillated. The magnetic flux at changes with time, and an eddy current is generated. The AC loss is caused by the temporal change of the magnetic flux generated by the eddy current in the superconducting coil and the inner tank. Therefore, there is a serious problem that the evaporation amount of liquid helium increases more than the capacity of the refrigerator mounted on the magnetic levitation train, and the superconducting magnet is quenched (transition from superconducting state to normal conducting state). To solve this problem, if the radiation shield is made of a material with low electrical conductivity so as to reduce the eddy current on the radiation shield, a substance with low electrical conductivity generally has low thermal conductivity. There was also a problem that a temperature gradient was generated in the shield itself, and the invasion heat due to radiation increased.

The present invention has been made in order to solve this problem, and an object of the present invention is to provide a superconducting magnet capable of reducing the heat generation in the inner tank of the superconducting magnet and the superconducting coil and reducing the evaporation amount of the refrigerant.

[0005]

In a superconducting magnet comprising an inner tank for accommodating a superconducting coil and a refrigerant, a radiation shield for covering the inner tank, and an outer tank for covering the radiation shield, the radiation shield has a low electric conductivity. And a member having high thermal conductivity is installed in a part of the radiation shield,
A cooling pipe is provided on the member having high thermal conductivity. Such means is used.

[0006]

Since the radiation shield is made of a substance having a low electric conductivity, the eddy current generated in the radiation shield can be suppressed even if the radiation shield vibrates with respect to the superconducting coil.
The time change of the magnetic flux generated by the eddy current in the superconducting coil and the inner tank becomes small, the AC loss in the superconducting coil and the inner tank becomes small, and the evaporation amount of the refrigerant can be greatly reduced.

Further, by sticking a substance having good heat conduction to the radiation shield, a large temperature gradient is not generated in the radiation shield itself, and the invasion heat can be reduced. Further, since the cooling pipe is joined to the member having high heat conductivity, it also has the effect of further increasing the cooling effect.

[0008]

1 is a plan view of an embodiment of the present invention. The radiation shield 1 is composed of a member 2 having a low electric conductivity, and a member 3 having a high thermal conductivity is divided and arranged on this surface. Further, the cooling pipe 4 is arranged so as to be connected to the member 3 having high thermal conductivity.

According to this embodiment, for the superconducting coil,
Even if the radiation shield 1 vibrates, since the radiation shield 1 is composed of the member 2 having a low thermal conductivity, the magnitude of the eddy current is suppressed. Therefore, there is an effect of reducing the AC loss in the superconducting coil and the inner tank due to the eddy current. Further, since the member 3 having high thermal conductivity is arranged, the radiation shield 1 does not have a large temperature gradient. Therefore, the invasion heat due to radiation can be reduced, and since the cooling pipe 4 is provided,
Further, the cooling effect is improved, and the evaporation amount of the refrigerant can be reduced.

As a modification of this embodiment, it is conceivable that the cooling pipe is meandered to increase the distance of the pipe. According to this embodiment, the eddy current flowing in the pipe can be suppressed,
Further, it has an effect of suppressing the evaporation amount of the refrigerant.

A plan view of another embodiment is shown in FIG. The radiation shield 1 includes a member 2 having a low electric conductivity and a member 3 having a high heat conductivity arranged on the member 2. An insulating material 7 is inserted into the bridging portion of the cooling pipe 4 that connects the further divided members 3 having high thermal conductivity.

According to this embodiment, in addition to the effects described above, the eddy current in the cooling pipe is limited, so that the AC loss due to the eddy current can be suppressed.

[0013]

According to the present invention, the eddy current generated in the radiation shield can be suppressed, the heat generation amount in the superconducting coil and the inner tank can be reduced, and the temperature gradient of the radiation shield itself can be suppressed to prevent the intrusion heat due to the radiation. It is possible to reduce the amount, and it is effective in suppressing the evaporation amount of the refrigerant.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of the present invention.

FIG. 2 is a perspective view showing a conventional example.

FIG. 3 is a plan view of another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Radiation shield, 2 ... Member with low electrical conductivity, 3 ... Member with high thermal conductivity, 4 ... Cooling piping, 5 ... Stopper, 6 ... Member with high electrical conductivity, 7 ... Insulator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayuki Shibata 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory Ltd. (72) Inventor Hideshi Fukumoto 1168 Moriyama Town, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. (72) Teruhiro Takizawa Inventor, Teruhiro Takizawa 4-6-6 Sugawadai Kanda, Chiyoda-ku, Tokyo Inside Hitachi, Ltd.

Claims (3)

[Claims] 1. A superconducting magnet device comprising an inner tank for accommodating a superconducting coil and a refrigerant, a radiation shield for covering the periphery of the inner tank, and an outer tank for covering the radiation shield.
The radiation shield is made of a material having low electric conductivity,
A superconducting magnet, wherein a member having high thermal conductivity is attached to the radiation shield, and a cooling pipe is joined to the member having high thermal conductivity. 2. The superconducting magnet according to claim 2, wherein a part of the cooling pipe in the transition portion between the members having high thermal conductivity is an insulator. 3. The superconducting magnet according to claim 1, wherein the cooling pipe meanders.