JPH0697515A - Very low temperature insulating container - Google Patents

Abstract

PURPOSE:To keep small an eddy current loss even under a fluctuating magnetic field to acquire excellent heat insulating performance by providing a composite structure consisting of a high resistance non-metal material layer and a metal structure material layer for a thermal shielding plate. CONSTITUTION:The basic operations of an ultra-low temperature insulating container are same as that of the prior art, that is, it can avoid thermal convection with installation of vacuum spaces 6a, 6b and also can reduce the amount of radiation of heat to an inner vessel 2 by providing a heat shielding plate 4. But, generation of only small eddy current is permitted for operations by AC or pulse signal which brings about a large variation of magnetic field with time by using a ceramic layer 4a of a silicon carbide group having high resistance and high conductivity as the heat shielding plate 4. However, since use of only ceramic layer 4a of the silicon carbide group makes difficult application into the heat shielding plate 4 in various shapes, such ceramic layer 4a of the silicon carbide group is bonded to a metal structure material layer 4b with a bonding agent layer 4c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic heat insulating container for containing an object to be cooled such as a superconducting coil.

[0002]

2. Description of the Related Art FIG. 5 shows, for example, "Cryogenic Engineering Handbook".
FIG. 1 is a cross-sectional view showing a conventional cryogenic heat-insulating container shown in (Uchida Old Crane Co., Ltd., p. 307).
Is a superconducting coil as an object to be cooled, 2 is a superconducting coil 1
An inner container 3 for accommodating the above is liquid helium as a coolant liquid for cooling the superconducting coil 1, and 4 is a heat shield plate made of copper or aluminum surrounding the inner container 2.

Reference numeral 5 denotes the inner container 2 and the heat shield plate 4.
Is a first vacuum space, 6b is a second vacuum space, 7 is a service port for supplying / exhausting liquid helium 3, etc., 8 is an inner container 2 and a heat shield. A support structure for adiabatically supporting the plate 4, 9
Is a thermal anchor part.

Next, the operation will be described. First, regarding the cryogenic heat insulating container as described above, there are three factors of the heat load of the inner container 2, namely, heat conduction, heat convection, and heat radiation. this house,
The heat convection can be avoided by providing the first and second vacuum spaces 6a and 6b. On the other hand, the heat conduction component exists from the service port 7 and the support structure 8.
The heat radiation component is from the heat shield plate 4. Therefore, it is important to reduce these two components of heat conduction and heat radiation as much as possible.

Next, the function of the heat shield plate 4 will be described in detail. First, the heat shield plate 4 is provided so as to surround the inner container 2 via the first vacuum space 6a, and this is actively cooled. Thereby, the amount of heat radiation to the inner container 2 can be considerably reduced.

For example, if the heat shield plate 4 is cooled with liquid nitrogen, the amount of heat radiation can be about (78/300) ⁴ = 0.5% as compared with the case where the heat shield plate 4 is not provided. This is because the amount of heat radiation is proportional to the fourth power of the radiation surface temperature.

Therefore, the influence of the heat shield plate 4 is extremely large, and it can be understood that the installation of the heat shield plate 4 is an important heat insulating technique. The heat shield plate 4 may be cooled not only by liquid nitrogen but also by vaporized helium gas or a refrigerator.

Now, the basic property required as a material for the heat shield plate 4 is that the heat conductivity is large. That is, it is necessary to immediately transfer the heat load from the outer container 5 to the liquid nitrogen, the gas helium, the refrigerator, etc., and to keep the heat shield plate 4 itself at a uniform temperature. Therefore, copper or aluminum is usually used as the heat shield material 4.

[0009]

Since the conventional cryogenic heat-insulating container is constructed as described above, the superconducting coil 1 will fluctuate when the number of cases where the superconducting coil 1 is used in AC operation or pulse operation increases. When exposed to a magnetic field, an eddy current is excited in the heat shield plate 4, and this eddy current causes Joule heat.

Generally, the smaller the electric resistance, the larger the eddy current, and the eddy current heat generation is given by (eddy current) ² × (resistance). Therefore, the smaller the electric resistance, the larger the eddy current heat generation. Therefore, the conventional heat shield plate made of copper or aluminum has a problem that heat generation due to an eddy current becomes large when the superconducting coil is operated by alternating current or pulse, and the heat shield plate cannot be advantageously operated.

The invention of claim 1 has been made to solve the above-mentioned problems. Even when the superconducting coil is operated in alternating current or in pulse, the eddy current loss of the heat shield plate is reduced. The object is to obtain a cryogenic heat-insulating container that can be kept small and ensure excellent heat-insulating performance.

It is an object of the present invention to provide a cryogenic heat insulating container capable of preventing the high resistance non-metal material layer and the metal structural material layer from being separated from each other due to heat shrinkage.

It is an object of the present invention to provide a cryogenic heat insulating container capable of increasing the cooling efficiency in a portion of the high resistance non-metal material layer having a large heat load.

It is an object of the present invention to obtain a cryogenic heat insulating container in which a high resistance non-metal material layer can be economically and easily attached to a metal structural material layer.

[0015]

In a cryogenic heat insulating container according to the invention of claim 1, the heat shield plate has a composite structure comprising a high resistance non-metal material layer having a high thermal conductivity and a metal structure material layer. Is.

The cryogenic heat insulating container according to the invention of claim 2 is
The heat shield plate has a composite structure composed of a high resistance non-metal material layer having high thermal conductivity and a metal structure material layer partially having a stretchable portion.

The cryogenic heat insulating container according to the invention of claim 3 is
The heat shield plate has a composite structure composed of a high resistance non-metal material layer having a high heat conductivity and a metal structure material layer in which a high heat conductive metal is partially attached.

The cryogenic heat insulating container according to the invention of claim 4 is
The heat shield plate has a composite structure composed of a high resistance non-metallic material layer having a high thermal conductivity and a metal structural material layer which are divided into a plurality of sheets.

[0019]

In the cryogenic heat insulating container according to the invention of claim 1, even when the superconducting coil is operated by alternating current or pulse, the eddy current loss is suppressed to a small level by the heat shield plate having a high electric resistance, and the heat shield is also provided. It also satisfies the original thermal performance of the plate.

In the cryogenic heat insulating container according to the second aspect of the invention, the expansion and contraction portion of the metal structural material layer absorbs the heat shrinkage of the layer and prevents the layers from separating from each other.

In the cryogenic heat insulating container according to the third aspect of the present invention, the high thermal conductive metal absorbs the heat load that largely acts on a part of the high resistance non-metal material layer, and thus the high cooling efficiency is obtained. .

The cryogenic heat insulating container according to the invention of claim 4 uses a high resistance non-metallic material layer divided into a plurality of layers so that these can be attached to the metal structural material layer economically and easily. .

[0023]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a superconducting coil as an object to be cooled, 2 is an inner container in which the superconducting coil 1 is housed, 3
Is liquid helium as a coolant liquid for cooling the superconducting coil 1.

Further, 4 is a heat shield plate made of a composite material which surrounds the inner container 2, and 4a is a silicon carbide system used as a high resistance non-metal material layer having a high thermal conductivity of the heat shield plate 4. Ceramic layers 4b are metal structural material layers such as stainless steel in the heat shield plate 4, and 4c are adhesive layers for joining the silicon carbide ceramic layer 4a and the metal structural material layer 4b.

Further, 5 is an outer container for holding the inner container 2 and the heat shield plate 4 in the first vacuum space 6a and the second vacuum space 6b, and 7 is for supplying and exhausting liquid helium 3 and the like. The service port, 8 is a support structure for supporting the inner container 2 and the heat shield plate 4 in an adiabatic manner, 9
Is a thermal anchor part.

Next, the operation will be described. The basic adiabatic operation of the cryogenic adiabatic container configured as described above is the same as that of the conventional example, and regarding the thermal convection, the vacuum space 6 is used.
This can be avoided by installing a and 6b, and heat conduction and heat radiation can be reduced by providing the heat shield plate 4 to reduce the heat radiation amount to the inner container 2. However, by using the silicon carbide ceramic layer 4a having high resistance and high heat conductivity as the heat shield plate 4, generation of eddy current is prevented in AC operation or pulse operation in which the magnetic field fluctuates greatly with time. It can be made smaller.

However, since it is difficult to apply the silicon carbide type ceramic layer 4a alone to the heat shield plate 4 having various shapes as in the embodiment, the metal structure material layer such as stainless steel, which should be called a base material, is used. 4b is joined by an adhesive layer 4c.

In the above embodiment, the high resistance non-metal material is made of silicon carbide ceramics, but silicon nitride ceramics, magnesium oxide ceramics or fiber reinforced plastics may be used. As the metal structural material layer 4b, not only stainless steel but also other metal structural materials can be arbitrarily selected and used.

Example 2. FIG. 2 shows another embodiment of the present invention. In this structure, the metal structure layer 4b made of stainless steel or the like is provided with a corrugated portion 10 having a corrugated shape as a stretchable portion. The function of the heat shield plate 4 of the cryogenic heat insulating container configured as described above is the same as that described in the embodiment in FIG. However, since the silicon carbide-based ceramic layer 4a and the metal structural material layer 4b have different thermal contraction rates, if they are simply bonded, they will be separated from each other when cooled.

Therefore, the peeling can be prevented by providing the metal structure material layer 4b with the uneven portion 10 as an interference mechanism capable of absorbing the difference in heat shrinkage.

Example 3. FIG. 3 shows still another embodiment of the present invention. This is one in which a thin plate 11 made of copper as a highly heat conductive metal is joined to a part of the silicon carbide based ceramic layer 4a constituting the heat shield plate 4. No matter how high the thermal conductivity of a non-metallic material is, it is smaller than that of copper or aluminum. Therefore, if the heat load is large or there is a locally large portion, sufficient cooling performance cannot be ensured.

Therefore, by using the above-mentioned copper thin plate 11 as a highly heat conductive metal in the vicinity of the thermal anchor portion 9 or the support structure 8 having a large heat load, a sufficient heat shield function can be ensured. it can. Moreover, since the area under construction is small, eddy current loss can be suppressed to a small level. The metal plate used here may be copper, aluminum, gold, silver, or brass.

Example 4. FIG. 4 shows another embodiment of the present invention. Since it is extremely difficult to manufacture the silicon carbide based ceramic layer 4a as a large single plate material, a plurality of divided pieces of the silicon carbide based ceramic layer 4a are bonded to the metal structural material layer 4b serving as the base material to form a heat shield. It is a plate 4. As a result, the cost of the heat shield plate 4 and the heat insulating container can be reduced.

[0034]

As described above, according to the first aspect of the invention, the heat shield plate has the composite structure composed of the high resistance non-metal material layer having a high thermal conductivity and the metal structure material layer.
There is an effect that a good heat shield property can be ensured and a cryogenic adiabatic container with a small eddy current loss even when exposed to a fluctuating magnetic field can be obtained.

Further, according to the invention of claim 2, the heat shield plate has a composite structure composed of a high resistance non-metal material layer having high thermal conductivity and a metal structure material layer partially having a stretchable portion. There is an effect that a composite structure composed of a high resistance non-metal material layer and a metal structure material layer can be prevented from peeling due to a difference in thermal shrinkage.

According to the invention of claim 3, the heat shield plate has a composite structure comprising a high resistance non-metal material layer having high heat conductivity and a metal structure material layer having a high heat conductivity metal partially attached thereto. Even if there is a large local heat load such as a thermal anchor part, by joining a heat conductive metal to this part, it is possible to obtain a sufficient heat shield property. is there.

Further, according to the invention of claim 4, since the heat shield plate has a composite structure composed of a plurality of high resistance non-metal material layers having a high thermal conductivity and a metal structural material layer, it is large. Even if it is a heat shield plate or a shield plate having a complicated shape, there is an effect that it can be easily formed at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a cryogenic heat insulating container according to an embodiment of the invention of claim 1.

FIG. 2 is a sectional view showing a cryogenic heat insulating container according to an embodiment of the invention of claim 2;

FIG. 3 is a sectional view showing a cryogenic heat insulating container according to an embodiment of the invention of claim 3;

FIG. 4 is a sectional view showing a cryogenic heat insulating container according to an embodiment of the invention of claim 4;

FIG. 5 is a cross-sectional view showing a conventional cryogenic heat insulating container.

[Explanation of symbols]

 1 superconducting coil (object to be cooled) 2 inner container 3 liquid helium (refrigerant liquid) 4 heat shield plate 4a silicon carbide based ceramic layer (high resistance non-metal material layer) 4b metal structure layer 5 outer container 6a first vacuum Space 6b Second vacuum space 10 Expansion / contraction portion (uneven portion) 11 Thin plate (high thermal conductive metal)

Claims (4)

[Claims] 1. An inner container for containing a refrigerant liquid in which an object to be cooled, which is cooled to an extremely low temperature, is immersed, a heat shield plate surrounding the inner container via a first vacuum space, and a second heat shield plate. In a cryogenic heat insulating container having an outer container surrounded by a vacuum space, the heat shield plate has a composite structure composed of a high resistance non-metal material layer having a high thermal conductivity and a metal structural material layer. Cryogenic cryogenic container. 2. An inner container for containing a refrigerant liquid in which an object to be cooled for cooling to an extremely low temperature is immersed, a heat shield plate surrounding the inner container via a first vacuum space, and a heat shield plate for the second heat shield plate. In a cryogenic heat insulating container having an outer container surrounding the vacuum space, the heat shield plate is composed of a high resistance non-metal material layer having high thermal conductivity and a metal structural material layer partially having a stretchable portion. A cryogenic heat insulating container having a composite structure. 3. An inner container for containing a refrigerant liquid in which an object to be cooled for cooling to an extremely low temperature is immersed, a heat shield plate surrounding the inner container via a first vacuum space, and a heat shield plate for the second heat shield plate. In a cryogenic heat insulating container having an outer container surrounded by a vacuum space, the heat shield plate is a metal structural material in which a high resistance non-metal material layer having high heat conductivity and a high heat conductive metal are partially attached. A cryogenic heat-insulating container having a composite structure composed of layers. 4. An inner container for accommodating a coolant liquid in which an object to be cooled for cooling to an extremely low temperature is immersed, a heat shield plate surrounding the inner container via a first vacuum space, and a heat shield plate for the second heat shield plate. In a cryogenic heat insulating container having an outer container surrounded by a vacuum space, the heat shield plate is a composite of a high resistance non-metal material layer and a metal structure material layer having high thermal conductivity divided into a plurality of sheets. A cryogenic heat-insulating container characterized by having a structure.