JP2986972B2 - Radiation shield plate for superconducting magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A conventional superconducting magnet and a radiation shield plate will be described with reference to FIGS.

[0003] Superconducting magnets, and the superconducting coil 1 placed in the cooling container, and a vacuum container 3 accommodates Kutsugaetsu in that radiation shield 2, and this like in a vacuum it.

When the temperature of the superconducting conductor exceeds a critical temperature due to heat input, the superconducting coil 1 returns to a normal conducting state and generates heat. Therefore, heat generated in the superconducting coil 1 and the outside into the superconducting coil 1 are introduced. It is necessary to prevent and reduce invading heat as much as possible to maintain the superconducting coil 1 in a stable superconducting state.

A radiation shield 2 provided between the vacuum vessel 3 and the superconducting coil 1 is provided between the vacuum vessel 3 and the superconducting coil 1.
It reduces the amount of radiant heat to the substrate, and is usually made of a metal having good heat conductivity and a low emissivity.

When a fluctuating magnetic field acts on the superconducting magnet from the outside, an induced current flows through the vacuum vessel and the shield plate due to the fluctuating magnetic field. The shield plate vibrates due to the action of this induced current and the strong magnetic field of the superconducting magnet, generating heat in the superconducting coil (RTRI REPORT
Vol4, No1, 90,1).

As one of means for reducing the heat generation, a metal thin film 5 having a high thermal conductivity is formed on the surface of the substrate 4 made of a high electric resistance material.
In order to reduce the induced current generated in the thin film 5, a radiation shield plate has been proposed in which a plurality of partitions 6 are provided on the surface to constitute the radiation shield 2 (Japanese Patent Application No. 03385/1986).
No. 6).

[0008]

In general, since the high electrical resistance material has a low thermal conductivity, the temperature of the shield plate may increase and radiant heat to the superconducting coil may increase.
A metal thin film with high thermal conductivity is bonded to the substrate. However, since an induced current is generated in this metal, a partition is provided in the thin film to reduce the induced current. However, this partition is a factor that hinders heat conduction on the shield plate.

In view of the above, it is an object of the present invention to further reduce the heat generation and heat input of a superconducting coil and a coil container in a superconducting magnet subjected to a fluctuating magnetic field, and to improve the stability of the superconducting magnet.

[0010]

The present invention for the above purposes achieving Means for Solving the Problems] is between the superconducting coil and the vacuum container containing the same
In the above, a heat radiation shield by covering the superconducting coil
Forming an in radiation shield plate for a superconducting magnet, a sheet made of high thermal conductivity carbon fibers pitch-based, wherein the carbon
Multiple layers with different fiber orientations and impregnated with resin
It is characterized by having been configured to.

[0011]

[Action] physical properties of the carbon fibers is a large difference Te cowpea its manufacturing method, but as a carbon fiber having high thermal conductivity pitch-based resistivity of the fiber itself, be obtained to 700 mu Omega cm at the temperature of liquid nitrogen it can. This is 10 times better than stainless steel under the same conditions.
More than double. In addition, the sheet may be arranged in a manner that
It is composed by stacking multiple sheets in different directions and impregnating with resin.
Therefore, the anisotropy of the shield plate is reduced,
The formation of the distribution and the prevention of cracking during machining can be achieved.

Since the shield plate of the present invention is formed by impregnating the carbon fiber with a resin and molding it into a plate, the resistance of the shield plate becomes larger than this value, and the fluctuating current due to the external fluctuating magnetic field decreases.

On the other hand, the thermal conductivity of carbon fiber is 200 W at room temperature.
/ mk to 300W / mk, equivalent to copper. In order to form a shield plate, it is a unidirectional plate with a carbon fiber content of 60% depending on the composition ratio of carbon fiber and resin, and a thermal conductivity of 30 to 50 W / mk at liquid nitrogen temperature can be obtained. ing. This is the thermal conductivity of aluminum alloy (JIS-A5083) at the same temperature
Same as 56W / mk, thermal conductivity of stainless steel 8W / m
It is several times k.

That is, with the shield plate having this configuration, the induced current due to the externally fluctuating magnetic field can be reduced, and at the same time, the heat on the shield plate can be transmitted to the cooling section due to the high thermal conductivity. In addition, the metal deposited film on the shield plate to reduce radiant heat transfer has the thickness required to reflect light.
It should be about 0.1 μm to 0.2 μm. Therefore, since the electrical resistance of this portion is large, it is not necessary to provide a partition in the film portion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A shield plate of a superconducting magnet according to the present invention will be described with reference to an embodiment shown in FIG.

The radiation shield plate 2 is formed by laminating a sheet 7 (7a, 7b, 7c) of a pitch-based high thermal conductivity carbon fiber and impregnating it with a resin to form a substrate 4 having a low radiation aluminum alloy on the surface thereof. , A metal film such as copper is deposited and the deposited layer 8 (8
a, 8b) to form the radiation shield plate 2.

In this embodiment, the carbon fiber sheet 7 is used as three sheets, and the radiation shield plate 2 is arranged from the upper side in the order of the vapor deposition layer 8a, the carbon fiber sheets 7a, 7b, 7c, the substrate 4 and the vapor deposition layer 8b. Then, three sheets of carbon fiber sheets 7a, b, and c having the fibers aligned in one direction are laminated in different directions.

Since the radiation shield plate 2 is configured as described above, the induced current due to the external magnetic field can be reduced, and at the same time, the temperature distribution on the radiation shield plate 2 can be reduced.

In this example, the direction of the carbon fiber sheet 7 is 1
The third sheet 7a is disposed in three directions of 0 °, the second sheet 7b is disposed in 90 °, and the third sheet 7c is disposed in three directions of 45 °. And cracks during machining are prevented.

By reducing the induced current of the shield plate 2 with respect to the externally fluctuating magnetic field, the heat generated in the superconducting coil and the coil container is reduced. Further, since the material of the radiation shield plate 2 has a high thermal conductivity, a large temperature distribution does not occur on the radiation shield plate 2 and the radiation rate of the surface of the shield plate 2 is small, so that the amount of radiation heat transferred to the superconducting coil container is reduced. Decrease.

[0021]

According to the present invention, in a superconducting magnet subjected to an externally fluctuating magnetic field, the amount of heat generated in the superconducting coil and the coil container caused by the induced current of the radiation shield plate is reduced, and the amount of radiant heat transferred from the shield plate to the superconducting coil container is reduced. Is small and a highly stable superconducting magnet can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a radiation shield plate according to the present invention.

FIG. 2 is a sectional view of a conventional radiation shield plate.

FIG. 3 is a perspective view of a superconducting magnet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Superconducting coil 2 Shield plate 3 Vacuum container 5 Substrate 7 Sheet of carbon fiber 8 Deposition layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 39/04

Claims (3)

(57) [Claims] 1. A there between the superconducting coil Toko Re vacuum vessel containing, in the greater conductivity by coil coating thermal radiation shield for a superconducting magnet radiation shield plate forming a high thermal conductivity carbon fibers pitch-based sheet, said to be from
Laminate multiple sheets with different carbon fiber placement directions and
A radiation shield plate for superconducting magnets, characterized by being impregnated . 2. The sheet according to claim 1, wherein the sheet has a temperature near the boiling point of liquid nitrogen.
Having a thermal conductivity λ of 20 W / m · K or more.
The radiation shield plate for a superconducting magnet according to claim 1. 3. A low-emissivity metal on the surface of the sheet.
Characterized by being deposited in a thickness range of 0.1 to 0.2 μm
3. The radiation for a superconducting magnet according to claim 1 or 2.
Shield plate.