JPH03218079A - cryostat - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a thermally insulating support for a cryostat.

[Conventional technology]

As described in Japanese Patent Publication No. 56-7413, conventional heat insulating supports change the material of the heat insulating material in two regions, high temperature and low temperature, and use glass fiber reinforced plastic in the high temperature region and carbon fiber reinforced plastic in the low temperature region. was using. Furthermore, there is a heat insulating support made of polyamide fibers and boron fibers, as described in JP-A-56-108288.

[Problem to be solved by the invention]

Future cryostants will require even greater insulation performance, and conventional insulation supports have not been sufficient.

The present invention reduces heat intrusion by using fiber reinforced plastic (hereinafter referred to as FRP) made of Si-Ti-C-0 fibers, which exhibits low thermal conductivity in the region between room temperature and liquid helium temperature, as a heat insulating material. I can do it.

The purpose of the present invention is to use a superconducting magnetic resonance imaging system (hereinafter referred to as MRI).
) and superconducting magnetic levitation trains, etc., to improve the insulation performance of cryostants.

[Means to solve the problem]

To achieve the above objectives, Si-Ti-C-0 fibers with high specific strength and low thermal conductivity are impregnated with epoxy resin.
-Ti-C-0/FRP material is used as a heat insulating support at extremely low temperatures.

[Effect]

High specific strength Is i -T i -C-0/FRP (
7) The material is conventional glass fiber reinforced plastic (hereinafter referred to as G
FRP) and carbon fiber reinforced plastic (hereinafter referred to as CFRP)
Both are temperature ranges with high thermal conductivity (approximately 40K-10K)
It has the characteristic of low thermal conductivity. By using this material as a heat insulating support for superconducting magnets such as MRI and superconducting magnetic levitation trains, which require high heat insulation performance, superior heat insulation performance can be obtained compared to conventional materials. Additionally, this reduces the amount of liquid helium consumed to cool the superconducting coils, which has the advantage of reducing the number of times liquid helium is injected.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 shows a superconducting magnet for nuclear magnetic resonance (NMR) analysis. A high magnetic field and a highly uniform magnetic field are obtained by the superconducting coil 1. This superconducting coil is made of NbTi
Since it is made of superconducting wire (niobium titanium), it needs to be cooled to about 4.2 K with liquid helium 2. Since this liquid helium 2 evaporates with a small amount of heat entering, the amount of consumption of liquid helium 2 is reduced by improving insulation. 3 is a 40K radiation shield that shields the liquid helium tank 2a from directly entering the liquid helium tank 2a from the high temperature surface. Further, 4 is a nitrogen shield equipped with a liquid nitrogen tank 5, which maintains its temperature at about 80K. 6 is liquid nitrogen, which evaporates with a small amount of heat entering like liquid helium, so a laminated heat insulating material 7 is attached to the outer periphery of the nitrogen shield 4 to shield heat radiated from the room temperature surface (vacuum container 8). The liquid helium tank 2a is surrounded by multiple radiation shields in this way, and the interior of the vacuum container 8 is maintained at a high vacuum (below 10-' Torr) to reduce the amount of heat that enters the liquid helium 2. ing. This superconducting magnet also needs to withstand transportation. For this reason, the nitrogen shield 4, 40K shield 3 and liquid helium tank 2a are fixed with a heat insulating support,
As mentioned above, it is important to reduce the amount of heat intrusion. For this reason, it is essential that this heat-insulating support has low thermal conductivity and is made of a high-strength material. Figure 2 shows CFRP, GFRP and S i -T i -C-0/
This shows the temperature characteristics of FRP's thermal conductivity. Here, S
i-Ti-C-0 fibers contain 45-53% silicon, 25-53% silicon
It is a material with an amorphous structure consisting of 33% carbon, 15-20% oxygen, and 1-5% titanium. CF from Figure 2
RP is 40K or less, GFRP is 100K or more, and Si-Ti-C-0/FRP is . 40K to 1
It can be seen that this material has the lowest thermal conductivity in the intermediate temperature range up to 00K. Further, since the tensile strength of this Si-Ti-C-0 fiber is as high as 2740 MPa, it can be seen that the fiber has high strength and is excellent as a material for a heat insulating support.

Reference numeral 9 in FIG. 1 is a high-temperature heat-insulating support that fixes the nitrogen shield 4 (80K) to the vacuum container (approximately 300K). This material is GFRP.

Reference numeral 10 denotes a medium-temperature insulation support for connecting and fixing the nitrogen shield 4 and the 40K shield 3, and is made of Si-Ti-C-0/FRP. 11 is a low-temperature insulating support that connects and fixes the 40K shield 3 and liquid helium tank 2a;
It is made by RP. As can be seen from Fig. 2, each of the heat insulating supports shown in Fig. 1 becomes a heat insulating support with the least conductive heat by taking advantage of its respective thermal conductivity characteristics. In addition, from this, it becomes a superconducting magnet with higher heat insulation performance than conventional ones,
This has the advantage of requiring less liquid helium consumption.

In addition to this effect, the re-injection time of liquid helium can be maintained for a long time, and the cost of liquid helium can be reduced. 3 and 4 are enlarged views of the embodiments of the respective insulating supports 9, 10, 11 shown in FIG. 1. Third
The figure shows a ring shape. FIG. 4 shows hooks 12 attached to both ends of the FRP material.

FIG. 5 is a cross-sectional view of a superconducting magnet for MRI according to another embodiment of the present invention. 12 is a small helium refrigerator at 80K
It has two cooling parts: 1 and 40K. l3 is 80K cooling section 1
4 is the 40K cooling section. This superconducting magnet for MRI is
By installing the refrigerator 12, the amount of liquid helium 2 consumed is reduced. Nitrogen shield 4 in 80K cooling section 13
The 40K shield 3 is thermally coupled to the 40K cooling section, and the respective temperatures are maintained at 80K and 40K.

Even in this case, the high temperature insulation support 9 is placed between the vacuum container 8 and the nitrogen shield 4, and the medium temperature insulation support 10 is placed between the nitrogen shield 4.
and the 40K shield 3, the low temperature insulation support 11 is 40K
It is installed between the K shield and the liquid helium tank 2a to reduce heat intrusion due to conduction from the heat insulating support.

FRP made of Si-Ti-C-0 fibers has high specific strength and has low thermal conductivity compared to other composite materials, so it can be used as a heat insulating support from room temperature to low temperature. It is also possible to use it as

〔Effect of the invention〕

According to the present invention, CFRP, Si-Ti-C-0/FR
Based on the temperature characteristics of the thermal conductivity of P and GFRP, it is possible to minimize the heat intrusion from the heat insulating support by combining the heat insulating support so that the temperature range where the thermal conductivity is the lowest is achieved. .

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a superconducting magnet for NMR according to an embodiment of the present invention, FIG. 2 is a temperature characteristic diagram of thermal conductivity of the heat insulating support material of the superconducting magnet, and FIGS. 3 and 4 are: FIG. 5, a front view showing the structure of the heat insulating support, is an MRI image of another embodiment of the present invention.
FIG. 3 is a cross-sectional view of a superconducting magnet for use. 9... High temperature adiabatic support, 10... Medium temperature adiabatic support,
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Claims (1)

[Claims] 1. Glass fiber reinforced plastic is used in the temperature range of 100K or more, carbon fiber reinforced plastic is used in the temperature range of 40K or less, and Si- is used in the temperature range of 40K to 100K.
A cryostat characterized by using a heat insulating support made of fiber-reinforced plastic made of Ti-C-O fibers.