JPH0555807B2 - - Google Patents

Description

Detailed Description of the Invention [Object of the Invention] The present invention relates to a liquid helium level meter that measures the level of liquid helium in a container made of metal or glass. This relates to improvements to the detection unit.

[Prior art]

Regarding a conventional liquid level meter for measuring the level of liquid helium in a container, there is a specification of Japanese Patent Application No. 1982-220076 (Japanese Patent Application No. 1-14522) entitled ``Liquid Helium Level Gauge.''

To explain this technology using Figure 1, 1 is a liquid level gauge, 2 is a case with a built-in power supply and measurement circuit,
3 is the stainless steel pipe of the detection part, 4
is the support part. The inner surface of the pipe 3 is covered with an electrically insulating and heat insulating material layer 3a, and an electrical resistance wire 5 and a lead wire 6 connected to the lower end of the electrical resistance wire 5 are installed in the inner space of the electrically insulating and heat insulating material layer 3a. It is located. The electrical resistance wire 5 is made of an amorphous superconducting alloy of zirconium and rhodium, has a ribbon shape, and has a superconducting transition temperature equal to that of liquid helium.
It is approximately equal to 4.2K. Note that when the pipe 3 is inserted into liquid helium, liquid helium enters the pipe 3, and the liquid level inside and outside the pipe 3 becomes the same.

[Problems with conventional technology and their technical analysis]

The conventional liquid level gauge shown in FIG. 1 uses a stainless steel pipe as an outer cylinder in the liquid helium detection section. This is to maintain the rigidity of the detection section and provide reliability when temporarily and easily measuring liquid helium in a metal or glass container. However, (1) the heat capacity of the pipe 3 is large, and liquid helium evaporates significantly due to the heat of the detection part inserted into the container; and (2) the thermal conductivity of the pipe 3 is high, so If it is immersed constantly or for a long time, it will not be able to be insulated from the outside room temperature, allowing a large amount of heat to enter, and will consume a large amount of liquid helium.
(3) Since the pipe 3 is a conductor, electrical insulating material was coated or interposed on the inner surface of the pipe to prevent electrical resistance wires from short-circuiting; (4) Due to the high thermal conductivity of the pipe 3, a heat insulating material is provided on the inner surface of the pipe to increase the heat retention effect of the electrical resistance wire. However, when a long detection part is used, the pipe often bends during use, and the electrical resistance wire is not necessarily located in the center of the pipe, but often comes into contact with the inner surface of the pipe. In this case, heat is taken away from or applied to the electrical resistance wire, which causes measurement errors.

[Technical issues]

Therefore, the present invention aims to improve the structure of the detection part of a continuous liquid level gauge that measures the level of liquid helium to a detection part with small heat capacity, low thermal conductivity, and good insulation. This is an issue to be addressed.

[Technical means]

The technical means taken by the present invention to solve the above-mentioned technical problem is that a superconducting alloy having an amorphous alloy phase as its main structure is stretched almost vertically as an electrical resistance wire and immersed in liquid helium to make it superconducting. In a liquid helium level gauge that continuously displays liquid level detection using a transition phenomenon, a part of the surface of a support part formed into a rod shape from a resin composite material mixed with fibers with low thermal expansion and contraction is used. The film is made of zirconium and rhodium (composition with a zirconium ratio of 72.5 to 77.5 at.%) using vacuum film-forming techniques such as vacuum evaporation, sputtering, and ion plating.
Superconducting transition temperature is 4.2K, close to liquid helium temperature
An amorphous superconducting alloy thin film with a temperature of ~4.5K is formed in a straight or spiral shape, an electrical resistance wire is formed from this straight or spiral amorphous superconducting alloy thin film, and one lead wire for measuring electrical resistance is formed. Wiring passes through the support part to the electrode at the end, the other electrode is provided in the support part, and the electrode at the end is embedded in the indicator part.

Here, vacuum film forming techniques such as vacuum evaporation, sputtering, and ion plating form an amorphous structure at the same time as forming the thin film structure of the amorphous superconducting alloy thin film.

[Effect of technical means]

The above technical means works as follows. That is, on a part of the surface of the support part formed into a rod shape from a resin composite material mixed with fibers with low thermal expansion and contraction,
Using vacuum film-forming techniques such as vacuum evaporation, sputtering, and ion plating, an amorphous superconducting alloy thin film made of zirconium and rhodium and having a superconducting transition temperature of 4.2K to 4.5K, which is close to the temperature of liquid helium, is formed into a straight or spiral shape. Since the electrical resistance wire is formed from this linear or spiral amorphous superconducting alloy thin film, the amount of liquid helium in the container (height above the container) can be measured continuously. Thin film (10 μm or less) of amorphous superconducting alloy that is electrical resistance wire
Because it is in close contact with the support made of resin-based composite material, it has a small heat capacity and extremely little heat intrusion from outside room temperature. The amount of liquid helium consumed is less than half that of the conventional method. In addition, since the amorphous superconducting alloy thin film is closely adhered to and integrated with the resin composite material of the support part, and the lead wires are also penetrated and embedded, there is no bending or damage to the electrical resistance wires or lead wires. Furthermore, it is extremely stable against transportation and vibration, and is a durable and reliable liquid level gauge that can perform continuous measurement.Furthermore, the electrode at the end is embedded in the supporting part of resin composite material. Especially compact and reliable,
This is a liquid level gauge with a structure that is difficult to damage.

[Special effects produced by the present invention]

The present invention has the following unique effects: (1) Vacuum deposition, sputtering, By vacuum film forming technology such as ion plating, an amorphous superconducting alloy thin film made of zirconium and rhodium and having a superconducting transition temperature of 4.2K to 4.5K, which is close to the liquid helium temperature, is formed in a linear or spiral shape,
Since the electric resistance wire is formed by the linear or spiral amorphous superconducting alloy thin film, the diameter of the support part can be made small (1 to 5 mm), and measurements can be made in a small size and with a small current.

(2) The thickness of the amorphous superconducting alloy is 20 μm in the conventional ribbon-like case, but it is less than 10 μm in the case of the thin film of the present invention, and the resistance value is more than double, which increases the sensitivity of the detection part. very good.

(3) Because of its simple structure, it can be manufactured at a very low cost, and because it is almost unbreakable, it is convenient to transport.

(4) Made of zirconium and rhodium, the superconducting transition temperature is 4.2K to 4.5K, close to the liquid helium temperature.
By using an amorphous superconducting alloy that is niobium,
This is less than one-tenth that of titanium-based superconductors (superconducting transition temperature 10K). Therefore, evaporation of liquid helium due to the small amount of heat required for measurement can be suppressed as much as possible. In particular, by providing an electrical resistance wire made of a superconductor on the surface of the resin composite support material, the transition occurs steeply at the part that directly touches the liquid surface, resulting in extremely good followability and highly accurate measurement. becomes possible.

(5) When FRP (fiber-reinforced resin) is used as the resin-based composite material for the support part, if the outer diameter of the support part is as small as a few mm or less, it is possible to bend to some extent and deform within an elastic range. It can also be used in cases where the bottom surface is not directly below the liquid level insertion port or where the introduction pipe into which the liquid level system is inserted is not straight.

〔Example〕

An example illustrating a specific example of the above technical means will be described below.

In Fig. 2, 1 is a liquid helium level gauge, 2
10 is an electrical resistance measurement unit with a built-in electronic circuit;
The support part is made of FRP. 11 is an electric resistance wire, which is vacuum-deposited on a part of the surface of the support part 10;
Using vacuum film-forming techniques such as sputtering and ion plating, an amorphous superconducting alloy thin film consisting of zirconium and rhodium is formed in a linear shape.
An electrical resistance wire is formed from this linear amorphous superconducting alloy thin film. The superconducting transition temperature of this amorphous superconducting alloy thin film is 4.42 K when the proportion of zirconium is 75 at%, and the superconducting transition temperature is 4.42 K when the proportion of zirconium is 74 at%.
The temperature is 4.40K for the composition, and 4.22K for the composition with a 73 atomic percent zirconium content. Electrodes 12 and 13 are made of brass and are embedded in the support portion 10.
14a and 14b are lead wires, which are connected to the support part 10.
embedded in. The lead wire 14a passes through the center of the round bar and is connected to the electrode 12.

In the above configuration, the operation is explained as follows.
If the detection part 10 of the liquid level gauge is inserted into liquid helium, the liquid level is A, and the end electrode 12 of the detection part is B, the electrical resistance between A and B becomes 0, and therefore other If the electrode is C, the electrical resistance of A to C will be measured, and the vertical distance between A to B and A to C, that is, the height of the liquid helium in the container will be displayed on the meter. Furthermore, even if the A point changes, it is displayed continuously.

[Brief explanation of the drawing]

FIG. 1 shows a conventional example, in which A is an external perspective view and B is an enlarged sectional view of the main part. FIG. 2 shows an embodiment of the present invention, in which A is a schematic explanatory diagram, B is a perspective view of the lower electrode, C is a side sectional view of B, and D is a side sectional view of the upper electrode. . 1... Liquid level gauge, 10... Support member, 11... Electric resistance wire, 12, 13... Electrode, 14a, 14b
……Lead.

Claims (1)

[Claims] 1. A superconducting alloy having an amorphous alloy phase as its main structure is stretched almost vertically as an electrical resistance wire, and is immersed in liquid helium to continuously detect the liquid level using the superconducting transition phenomenon. In a level gauge for liquid helium that displays as Using the vacuum film forming technology of An electrical resistance wire is formed from a shaped amorphous superconducting alloy thin film, one lead wire for measuring electrical resistance is routed through the support part to an electrode at the end, and the other electrode is provided on the support part. A liquid helium level gauge with an electrode at the end embedded within the support.