JPH03142909A - Cryogenic vessel - Google Patents

Abstract

PURPOSE:To assure the reduction in eddy current and the enhancement of safety by a method wherein at least either one out of a helium vessel or a vacuum vessel is formed into a layer structure of a thin wall sheet. CONSTITUTION:The title cryogenic vessel is formed by winding up a helium vessel 3A and a vacuum vessel 4A with a stainless steel thin sheet 3a and then the initial end and the terminal end of the winding are fixed by welding process to be airtightly sealed. Normally, an oxide film is formed on the surface of the stainless steel sheet 3a having the same effect as respective layers are electrically insulated. Accordingly, within the helium vessel 3A and the vacuum vessel 4A, the two layers of the innermost layer and the outermost layer shortcircuited at the welded part are formed of only one turn so that the electric resistance in the circumferential direction may be notably increased comparing with the case of no layer formation. Through these procedures, either the rapid conduction of superconductive coil 1 or the eddy current due to the rapid conduction can be reduced for cutting down the electromagnetic force due to the eddy current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cryogenic container, and particularly to a cryogenic container housing a superconducting coil that rapidly charges and discharges.

[Prior Art] Fig. 3 shows a conventional cryogenic container disclosed in, for example, Japanese Patent Application Laid-Open No. 60-147000, in which the superconducting coil (1) is made of stainless steel and contains liquid helium (2). It is stored in a helium tank (3).

A vacuum region (5) is formed between the helium tank (3) and a stainless steel vacuum tank (0) surrounding it.

The superconducting coil (1) is suspended and supported by a support structure (6).

The liquid helium tank (3) is vacuum insulated by the vacuum region (5) and kept at an extremely low temperature.

Next, the effect will be explained. When the superconducting coil (1) is rapidly energized or de-energized, eddy currents are induced in the surrounding metal bodies. Among them, the helium bath (3) is closest to the superconducting coil (1), so that the largest eddy current is induced among the members constituting the cryogenic container. When the eddy current flows through the helium (3), an electromagnetic force is generated between the superconducting coil (1) and the helium bath (3) due to interaction with the current flowing through the superconducting coil (1).

[Problem to be solved by the invention] In the conventional cryogenic container as described above, helium bath (3
), it is difficult to construct a strong support structure, so excessive stress is generated due to electromagnetic force, which in extreme cases can lead to destruction. In addition, excessive force is applied to the support structure (6) of the superconducting coil (1), resulting in damage.

This invention was made to solve the above-mentioned problems, and aims to reduce eddy currents and thereby obtain a highly safe cryogenic container.

[Means for Solving the Problems] The cryogenic container according to the present invention has at least one of the helium tank, that is, the cryogenic refrigerant storage tank and the vacuum tank,
It has a layered structure made of thin metal.

[Function] In this invention, the electrical resistance of the helium tank and the vacuum tank is increased, and the eddy current when the superconducting coil is rapidly energized or cut off is reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In Fig. 1, structures other than the helium tank (3A) and vacuum tank (4A) are shown in Figure 3, which describes the conventional technology.
It is the same as the one shown in the figure. In this example, a helium bath (
3A) and the vacuum chamber (4A) are formed by rolling and layering thin plates of stainless steel, for example.

Next, the effect will be explained. The above structure is a helium tank (
Is the same true for 3A) and the vacuum chamber (4A)? ,
CO), and the cross section of the helium tank (3A) is
This will be explained using a diagram. In Fig. 2, a thin stainless steel plate (3a) is rolled up, and its winding start end (3b) and end end (
3c) is fixed by welding and hermetically sealed. Usually, there is an oxidized layer on the surface of a stainless steel plate, which has high electrical resistance, so each layer has the same effect as electrical insulation. Therefore, in the helium tank (3A), the two layers, the innermost layer and the outermost layer, which are short-circuited at the welding part, only form an electrical L-turn, so the electrical resistance in the circumferential direction is significantly lower than when no layers are formed. Increase.

On the other hand, the internal pressure in the helium tank (3A) is
Although the external pressure of atmospheric pressure acts on the material, the strength against these pressures is determined by the layered wall thickness, so the layered structure does not result in a decrease in strength.

In this way, since the circumferential electrical resistance between the helium tank (3A) and the vacuum m (4A) is large, the eddy current caused by rapid energization or rapid discharge of the superconducting coil (1) is greatly reduced, and therefore, the eddy current caused by the eddy current is greatly reduced. Electromagnetic forces are also significantly reduced. Therefore, the force and stress acting on the helium tank (3A), the vacuum tank (4^), and the support structure (6) of the superconducting coil (1>) are weak and are structurally safe.

Furthermore, heat generation in the helium tank (3^) due to eddy currents is also reduced, and consumption of expensive refrigerant is also saved.

In addition, in the above embodiment, a helium tank (3A) and a vacuum tank (
Although both of 4^) are stratified, only one of them may be stratified.

Further, in the above embodiment, no electrical insulating material was provided between the laminated layers, but a thin electrical insulating film may be inserted between the layers, or the surface of the thin plate (3a) may be electrically insulated. It is also possible to actively apply an insulating film.

[Effects of the Invention] As described above, according to the present invention, since at least one of the helium tank and the vacuum tank has a layered structure of thin plates, eddy current can be reduced and safety can be improved.

[Brief explanation of the drawing]

FIG. 1 is an elevational view of an embodiment of the present invention, FIG. 2 is a partially sectional plan view of the same, and FIG. 3 is an elevational elevational view of a conventional cryogenic container. (3A)...Helium tank (cryogenic refrigerant storage tank), (3a
)... Thin plate, (4A)... Vacuum chamber. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a cylindrical cryogenic container having a vacuum insulation structure consisting of a cryogenic refrigerant storage tank and a vacuum chamber, at least one of the cylindrical part of the cryogenic refrigerant storage tank and the cylindrical part of the vacuum tank is stratified with a thin metal wrapped around it. A cryogenic container characterized by being