JPS59121986A - Cryogenic magnetic shielding vessel - Google Patents

Abstract

PURPOSE:To reduce magnetic flux density from the quantum efficiency of a superconducting material by forming a superconducting state by oppositely combining two cylinders and increasing total internal volume by sliding the external cylinder. CONSTITUTION:A superconducting shielding vessel 1 made of a superconducting material such as Pb, Nb and an Nb-Ti alloy and the like is arranged in a case 3 made of a heat-insulating material together with an external vessel 2 made of a high permeability material, and the cryogenic magnetic shielding vessel (A) is formed. The external vessel 2 is prepared by the high permeability material, such as permalloy, permendur, etc., and a through-hole 5 into which liquid helium 4 flows is formed at the center of the bottom of the vessel 2. The external cylinder 1a and the internal cylinder 1b are constituted so as to be freely slid mutually, and encased into the case 3 together with the external vessel 2, and liquid helium 4 is charged into the case 3. When the superconducting shielding vessel 1 is brought to the superconducting state, the external cylinder 1a is pulled up. The internal volume is increased through the operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a magnetic shielding container for cryogenic temperatures that shields a magnetic field by applying the quantization effect of a superconducting material.

(2) Technical background In computers using Soyosefson devices,
To achieve superconductivity, it must be brought to extremely low temperatures.

For this purpose, the main frame of the combeater is immersed in liquid helium (4.2°K). In addition, since it is necessary to remove the main frame of the combeater from an external magnetic field and reduce it to an extremely low magnetic field, a superconducting shield made of a superconducting material is provided in liquid helium. Earth's magnetic field is 0.3
It is said that an ultra-low magnetic field of 10-6 G is required, although it is about 0.5 G.

(3) Prior art and problems A Josephson combinator is placed in liquid helium and surrounded by a superconductor container for magnetic shielding.

A ferromagnetic shield, which surrounds the outside of the superconductor container with a container of high magnetic permeability material, is used to reduce the magnetic field during cooling.

Regarding superconducting shielding containers in cryogenic magnetic shielding containers having such a structure, the bladder (Bla, dder) method, which applies the Meissner effect, and 90-.

The balloon method was widely used. In these methods, lead (Pb), which is a superconducting material, is folded to form a material, which is then expanded to form a superconducting shielding container, which is the inner container. However, when using this method, there are disadvantages in that strain is introduced from the cut and folded portions) and the magnetic field enters from there. Therefore, the conventional structure has insufficient magnetic shielding.

(4) Object and Structure of the Invention An object of the present invention is to provide a magnetic shielding container for cryogenic temperatures that can eliminate such conventional drawbacks and enhance the magnetic shielding effect. To achieve such an object, the present invention provides a superconducting shielding container for a cryogenic magnetically shielding container containing a cryogenic liquid with a two-electric structure of an ultra-low 4 shielding container and an outer strong magnetic shielding container. The container is constructed by overlapping parts of double cylinders made of superconducting material so that they can slide freely in the axial direction.
Here and there/＋! It is assumed to be f-symptom.

As mentioned above, the present invention applies the quantization effect of superconducting materials, and this principle is expressed as the magnetic flux density in the container x cross-sectional area, and the content is that the value is constant. That is. Based on this principle, the present invention attempts to dilute or shield the magnetic field by, for example, combining cylindrical cylinders in a pattern to increase the same volume.

(5) Embodiment of the Invention An embodiment of the invention will be described below with reference to FIGS. 1 to 3.

Figure 1 shows ultra-low conductivity shielding container 1 used for uninvented containers.
FIG. 2 is a perspective view of the super-sealing container 1 in use. As is clear from FIGS. 1 and 2, the outer tube 1a and the inner tube 1b are shown in FIG. , and are able to slide freely relative to each other in the axial direction. The ultra-low conductivity shielding container 1 is made of superconducting materials such as lead (Pb), niobium (Nb), and niobium-titanium (Nb-TI) alloy.

The ultra-low conductivity shielding container 1 configured in this manner is placed in a case 3 made of a heat insulating material together with an outer container 2 made of a high magnetic permeability material, thereby forming a magnetic shielding container A for cryogenic temperatures.

The outer volume is made of a high magnetic permeability material such as i 21ti /4-Malloy, Yamendale, etc., and a through hole 5 through which liquid helium 4 flows is provided at the center of the bottom.

Now, the ultra-low conductivity shielding container 1 is assembled with a cylinder made of lead with a thickness of 0.5 m and an inner diameter of 100 m and a length of 150 m + n, and an outer cylinder 1 is assembled as shown in FIGS. 1 and 2.
A and the inner cylinder 1b were configured to be able to slide freely relative to each other, and were housed in the case 3 together with the outer container 2. Next, liquid helium 4 was added. When the ultra-low conductivity shielding container 1 becomes superconducting, the outer cylinder 1a is pulled upward. This operation will increase the internal volume. Therefore, as understood from the above explanation, since the magnetic flux inside the cylinder is constant, the magnetic flux density decreases.For example, when cylinders with the above thickness, inner diameter, and length are combined Although the internal magnetic flux density was approximately 500 μG, as shown in FIG. 2, the outer cylinder 1a was stretched upward using a prescribed jig to a spacing of 270 mm to increase its internal volume.

The internal magnetic flux density in this state had decreased to about 300 μG.

(6) Effects of the Invention As explained above, the present invention, for example, combines two cylinders facing each other to form a superconducting state, and then slides the outer cylinder to increase the overall internal volume. The quantization effect of the superconducting material has the effect of reducing the magnetic flux density (0) Unlike conventional devices, the superconducting material (Pb, etc.) is not folded and unfolded for use, so the magnetic field enters from the folded part. The effect of diluting the magnetic field can be obtained extremely easily without the need for

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an ultra-low conductivity shielding container used in an embodiment of the present invention, FIG. 2 is a perspective view of the ultra-low conductivity shielding container in use, and FIG. 3 is a perspective view of the ultra-low conductivity shielding container used in an embodiment of the present invention. FIG. 1 is a sectional view showing an embodiment of the invention. 1... Ultra-low conductivity shielding container, 1a... Inner cylinder, 1b.
...Outer tube, 2...Outer tube, 3...Case, 4...
・Liquid helium.

Claims (1)

[Claims] 1. In a magnetically shielded container for cryogenic use that contains a cryogenic liquid with a double-layer construction of a superconducting shielded container and an outer ferromagnetic shielded container, the superconducting shielded container is made of two or more layers made of superconducting material. The above-mentioned magnetically shielded container for cryogenic temperatures, characterized in that parts of the cylindrical bodies are stacked on top of each other so as to be able to freely slide in the axial direction.