JPH0555808B2 - - 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. The present invention relates to an improvement of the detection section of the present invention.

[Prior art]

Regarding a conventional level gauge for measuring the level of liquid helium in a container, there is a publication entitled "Liquid Helium Level Meter" in Japanese Patent Application Laid-Open No. 55-85224, which shows a single-point detection type configuration. A conventional level gauge created based on this is explained with reference to Figure 1. 1 is a single point detection type level gauge, 2 is a detection section, 3 is a measurement section with a built-in electronic circuit, and 3a is a signal transmitter. Department.
4 is an electrical resistance wire made of a superconducting alloy made of niobium (Nb) and titanium (Ti), which is wound around a bobbin 5, and has a superconducting transition temperature of 10K. 6 is a lead wire.

[Problems with conventional technology and their technical analysis]

The conventional single-point detection type liquid level gauge shown in Figure 1 has a very large structure because an electrical resistance wire made of a superconducting alloy is wound around a bobbin, and therefore has a large heat capacity. A large amount of liquid helium is consumed when inserting it into the tank. Also, the diameter of the bobbin is several mm.
Because of its large size, the superconducting transition does not occur sharply when the liquid level is cut, and hysteresis tends to occur when the bobbin is raised and lowered, resulting in poor measurement accuracy. Next, the superconducting transition temperature is approximately 10K
Since the temperature is considerably higher than that of liquid helium (4.2K), the transition to superconductivity occurs well above the liquid level, resulting in large measurement errors. The superconducting state must be broken by winding electrical resistance wire and heating the bobbin away from the liquid surface. This mechanism increases the heat capacity of the bobbin and reduces the amount of helium evaporated by heating power. Significant. Furthermore, the electrical resistance tends to shift due to movement and vibration caused by carrying the liquid level gauge, resulting in a lack of reliability.

[Technical issues]

Therefore, the present invention aims to provide a single-point detection type liquid helium level gauge with a small heat capacity, a small amount of evaporation of liquid helium, a simple structure, high precision, and reliable liquid level gauge measurement. The technical challenge is to improve the detection section.

[Technical means]

The technical means taken by the present invention to solve the above-mentioned technical problems are disclosed in the inventors' earlier application (Japanese Patent Application No.
220076 "Special Publication No. 1-14522""Liquid Helium Level Gauge"), it is possible to apply vacuum evaporation, sputtering, ion plating, etc. on a glass, ceramic or alumite substrate. It is made of zirconium and rhodium (the proportion of zirconium is
An amorphous superconducting alloy thin film with a superconducting transition temperature of 4.2 K to 4.5 K, which is close to the liquid helium temperature (composition of 72.5 to 77.5 at. It is fixed to the end of the

Here, vacuum thin film 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. In other words, the superconducting transition temperature is the liquid helium temperature (4.2K)
Since we use an amorphous superconducting alloy consisting of zirconium and rhodium, which has a sharp transition width, a small absolute value of the temperature coefficient of electrical resistance, and high electrical resistance, it can be used at temperatures just above 4.2 K, just above the liquid surface. transition,
Very little heating power is required to break the superconducting state and reduce measurement errors, and depending on the usage conditions, the heating mechanism itself may not be necessary. Next, an amorphous superconducting alloy thin film is formed on a substrate made of glass, ceramic, or alumite, and an electrical resistance element is formed from this amorphous superconducting alloy thin film and fixed to the end of the support member. Therefore, this electrical resistance element has a diameter of approximately 3φmm and a thickness of approximately 10μm or less, and can be formed extremely compact even considering the thickness of the substrate. It is cooled down to liquid helium temperatures, and at the same time consumption of heil by immersion is extremely low. Therefore, the superconducting transition of the element occurs with an extremely small displacement of about 1 mm or less, and the hysteresis due to the rise and fall of the element is extremely small and can be completely ignored in practical terms.

In addition to being able to perform highly accurate measurements in this way, if the support member is pipe-shaped, it is fixed with a caulking spring, or if it is rod-shaped, it is fitted with a socket type structure, making it simple, robust, and highly reliable. This is the structure of the detection section.

[Special effects produced by the present invention]

The present invention has the following unique effects: Since the electrical resistance element of the detection part as a liquid level gauge is a thin film, it has a high electrical resistance due to its thinness compared to ribbon material or wire material. Because it is easy to obtain and the resistance change caused by the superconducting transition is large,
It has the advantage that the accuracy of the detection circuit section is low and sufficient.

〔Example〕

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

In FIG. 2, 1 is a single-point detection type liquid helium level gauge consisting of a measurement section and a measurement detection section;
10 is a substrate made of glass, ceramic, or alumite and has a thickness of about 0.3 mm; 11 is an electrical resistance element;
14 is a lead wire. The electrical resistance element 11 is formed of an amorphous superconducting alloy thin film made of zirconium and rhodium by sputtering on the substrate 10, and has a thickness of about 10 μm.
The diameter is 3φmm, and the superconducting transition temperature is 4.42K for a composition with a zirconium ratio of 75 at%, 4.40K for a composition with a zirconium ratio of 74 at%, and 4.22K for a composition with a zirconium ratio of 73 at%. be. FIG. 3 shows the electric resistance element 11 and the substrate 10, 11a and 11b are soldered electrodes, and 11e is a zigzag resistance pattern. The substrate 10 provided with the electrical resistance element 11 has a fourth
In the case of the support member 12 made of stainless steel pipe as shown in Figure A, the substrate 10 is fixed with a caulking spring 15, and in the case of the support member 13 of a round bar made of resin composited with glass fibers as shown in Figure 4B, the support member Lead wire 14 and sockets 16a, 16b in 13
The protruding electrodes of the electrical resistance elements are fitted into the sockets 16a and 16b.

In the above structure, the soldered electrodes have a more reliable structure than the commonly used electrodes made of silver paste, and can withstand long-term use. Furthermore, when the electrical resistance element 11 and the substrate 10 made of the amorphous superconducting alloy thin film are immersed in liquid helium, the electrical resistance immediately becomes 0 and the signal on the meter section is activated, and when the electrical resistance element 11 and the substrate 10 are separated from the liquid helium,
The signal is interrupted and is very sensitive.

[Brief explanation of the drawing]

FIG. 1 is an explanation of a conventional example, with A being an external view and B being a sectional view of the main parts. FIG. 2 is a schematic explanatory diagram of this embodiment, FIG. 3 is an explanatory diagram of an electrical resistance element, A is a plan view, B is a sectional view from A to A of A, and A in FIG. 4 is a support part. It is an enlarged sectional view of a tip, and (b) is an enlarged sectional view of a support part tip of another example. 10...Substrate, 11...Electric resistance element, 12,
13...Supporting member.

Claims (1)

[Claims] 1. A single-point detection type liquid level gauge that detects the level of liquid helium by fixing an electrical resistance element made of a superconducting alloy whose main structure is an amorphous alloy phase to the end of a support member. A superconducting material made of zirconium and rhodium with a superconducting transition temperature of 4.2K to 4.5K, which is close to the liquid helium temperature, is formed on a glass, ceramic, or alumite substrate by vacuum thin film technology such as vacuum evaporation, sputtering, or ion plating. A detection section of a level gauge for liquid helium in which an amorphous superconducting alloy thin film is prepared and an electrical resistance element formed from the amorphous superconducting alloy thin film is fixed to an end of a support member.