JPS6073198A - Extremely low-temperature container - Google Patents

Abstract

PURPOSE:To prevent the degree of vacuum in a vacuum section from being deteriorated even at an increase of the temperature in inner hull by providing a liquid nitrogen storage section at the bottom of the inner hull of an extremely low-temperature container and storing a small quantity of liquid nitrogen at the lower layer of a refrigerant. CONSTITUTION:An extremely low-temperature container is constituted with an inner hull 1, an outer hull 2, and a vacuum section 3, a ring-like groove 1b is formed at the periphery of the plain bottom 1a of the inner hull 1, and liquid nitrogen is stored in this groove. When the evaporation of liquid helium progresses and the temperature is increased, liquid nitrogen 6 is evaporated, and the inner hull 1 is filled with its gas. Then, the helium gas in the inner hull 1 is expelled outside, thus helium gas is prevented from infiltrating into the vacuum section.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a cryogenic container used in a skid magnetic needle or the like.

(b) Prior art Generally speaking, the detection part (probe) of a skid magnetometer that performs weak magnetic measurements is stored in a cryogenic container containing liquid helium because the measurement principle is such that the measurement is carried out in a cryogenic state. be done. As shown in FIG. 1, this cryogenic container has a double structure formed by an inner shell 1 and an outer shell 2, and a vacuum part 3 of a predetermined width is formed between the inner shell 1 and the outer shell 2. Further, liquid helium 4 is stored as a cryogen in the inner shell 1, and the probe 5 of the skid magnetic needle is immersed in this liquid helium 4. The above inner shell 1 and outer shell 2 are FRI
) (glass fiber reinforced plastic). Conventionally, in the cryogenic container of this scale, as the liquid helium 4 in the inner shell 1 evaporates and approaches the empty state, the temperature of the inner shell 1 increases, and the temperature rise causes the formation of the inner shell 1.
The helium gas permeability of the RP increases, and the helium gas filling the inner shell 1 enters the vacuum section 3, reducing the degree of vacuum in the vacuum section 3. Therefore, even if new liquid helium is filled, This method has the disadvantage that the amount of evaporation increases, leading to early loss of expensive liquid helium II4, and that the function of the cryogenic container itself is degraded.

(C) Purpose The purpose of this invention is to maintain the vacuum even if the liquid helium in the inner shell evaporates and becomes completely empty, even if the temperature in the inner shell rises, as described in Section 2. The first step is to provide a cryogenic container with a low degree of vacuum.

(D) Structure In order to achieve the above object, the cryogenic container of the present invention has the following features:
A liquid nitrogen storage section is provided at the bottom of the inner shell, and a small amount of liquid nitrogen is stored in the layer below the cryogen such as liquid helium. When the cryogen such as liquid helium evaporates and becomes empty, the inner shell is is filled with nitrogen gas.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a sectional view of a cryogenic container showing one embodiment of the present invention. The cryogenic container of this embodiment has the same basic structure as that shown in FIG. 1, consisting of an inner shell 1, an outer shell 2, and a vacuum section 3. However, this cryogenic container has a ring-shaped groove 1 on the periphery of the flat bottom 1a of the inner shell 1.
This groove 1b is characterized in that liquid nitrogen 6 is stored in the groove 1b. After filling the groove 1b with liquid nitrogen 6, liquid helium 4 is injected into the inner shell 1.

However, when liquid nitrogen 6 or liquid lium 4 is injected and stored and the inside of the inner shell 1 is kept at an extremely low temperature, it exists as a solid. The volume of the groove 1b may be about 1/700 of the storage volume of the liquid helium 4.

Therefore, the shape of the groove 1b is not limited to a ring shape, but may be any shape as long as it can store an appropriate amount of liquid nitrogen 6.

However, it is desirable that the groove 1b be formed at a location where the probe 5 of the skid magnetometer can be inserted without any problem.

In this cryogenic container, as the liquid helium 4 evaporates and becomes empty, the temperature rises. Therefore, the solidified liquid nitrogen 6 evaporates, and the inner shell 1 is filled with the gas. Then, the helium gas in the ζ inner shell is expelled to the outside.

Therefore, it is possible to prevent helium gas from entering the vacuum section 3. Of course, nitrogen gas does not pass through the inner shell 1 formed of I''Rl). Therefore, the degree of vacuum in the vacuum section 3 can be maintained.

FIG. 3 is a sectional view of a cryogenic container showing another embodiment of the present invention. This example cryogenic container has a bottom 1 of the inner shell 1.
A is formed into a downwardly convex curved surface, and a partition plate 7 with a small hole 7a is installed between the lower ail 1 of the inner shell 1 and the bottom part 1a. Nitko Gas 6
It is characterized by storing. The partition plate 7 is provided for holding and positioning the inserted probe.

The effect of liquid helium 4 after evaporation is similar to that shown in FIG.

FIG. 4 is a sectional view of a cryogenic container showing still another embodiment of the present invention. In this embodiment, the bottom 1a of the inner shell 1 of the cryogenic container is formed into an upwardly convex curved surface, and liquid nitrogen 6 is stored in a recess 1d formed at the periphery of the bottom 1a. In this embodiment, since the central convex portion of the bottom portion 1a has the function of holding and positioning the probe to be inserted, a partition plate as shown in FIG. 3 is not necessary.

(f) Effects According to the cryogenic container of this invention, liquid nitrogen gas is stored at the bottom of the inner shell, and when the liquid helium is emptied, the inner shell is filled with nitrogen gas and the helium gas is expelled to the outside. Therefore, it is possible to prevent helium gas from entering the vacuum section, and to prevent deterioration of the vacuum section.

Therefore, the stored liquid helium can be used for a long time.

Furthermore, the number of times the vacuum section must be vacuumed can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional cryogenic container, and Fig. 2 shows an embodiment of the present invention. ! 3 and 4 are cross-sectional views of cryogenic containers showing other embodiments of the present invention. 1: Inner shell, 1a: Bottom of inner shell, ■b = Groove, 1d: Recess, 2: 1 shell, 3: , 6I empty space, 4: Liquid...lium, 6: Liquid nitrogen, 7: Partition Board Patent Applicant Shimadzu Corporation Agent Patent Attorney Shigeru Naka Toshihiro Figure 1 Figure 3 Figure 2 Figure 4 Revised 1a 1 Support

Claims (4)

[Claims] (1) It has a double structure with an inner shell and an outer shell made of glass fiber reinforced plastic, a vacuum section is formed between the inner shell and the outer shell, and a cryogen such as liquid helium is stored in the inner shell. A cryogenic container in which members to be kept at extremely low temperatures are immersed in this cryogen, characterized in that a liquid nitrogen storage section is provided at the bottom of the inner shell, and the liquid nitrogen of the boat is stored in the layer below the cryogen. cryogenic container. (2) The 44 cryogenic container according to claim 1, wherein the liquid nitrogen storage portion is a groove formed in the peripheral edge of the inner shell bottom plane. (3) In the liquid nitrogen storage section, the bottom of the inner shell has a downwardly convex curved surface, and a horizontal partition plate with small holes is provided above the curved bottom. A cryogenic container according to claim 1, characterized in that it is a formed part. (4) The liquid nitrogen storage portion is characterized in that the inner shell bottom has an upwardly convex curved surface, and is an open portion formed at the periphery of this curved bottom. cryogenic container.