JPH0129245B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid level gauge for measuring the level of liquid helium in a metal container. Conventional liquid helium level gauges use a superconducting wire made of Nb-Ti (niobium titanium) alloy as the liquid level detection element, but (1) the superconducting transition temperature (Tc) of the Nb-Ti superconducting wire is Because it is higher than the helium temperature, it becomes superconducting even just above the liquid surface, so in order to make it normal conductive, it is necessary to run a current (about 70 mA) and raise the temperature with Joule heat, which consumes a large amount of liquid helium (0.02/hou).
r degree). (2) Nb-Ti superconducting wire has low electrical resistance even in the normal conduction state, and in order to increase measurement sensitivity, the wire diameter must be made thinner (approximately 0.2φmm), and its mechanical strength, especially impact resistance, is weak. There is. In order to eliminate the above-mentioned drawbacks, the present invention uses an amorphous superconducting material produced by ultra-rapid solidification from a molten state as a liquid level detection element instead of the Nb-Ti superconducting material, and calculates the electrical resistance value at both ends. It detects the position of the liquid level by measuring, and among ZaMb(Q+Al)c-based superconducting materials as amorphous superconducting materials,
A material with a superconducting transition temperature of 4.2 to 5.0〓, which is approximately equal to the liquid helium temperature of 4.2〓, is used.
However, in the above formula, Z is one of Zr, Hf, or Ti, M is one or more of V, Nb, or Ta, and Q is one or more of Si, Ge, or Consisting of both types, a is in the range of 10 to 90 atom%, b is in the range of 80 atom% or less, c is in the range of 10 to 25 atom%, and Q is 2
Alloys containing an amorphous phase with a volume percentage of 20% or more and Q+Al
It is an alloy having a composition in which 12 atomic % or less of C, B, or Sn is substituted for a part of the alloy by one or more of C, B, and Sn, and also contains an amorphous phase with a volume fraction of 20% or more. Since the superconducting transition temperature of the superconducting material is almost the same as the liquid helium temperature, by adding a special heating mechanism such as a heater, it is not necessary to apply Joule heat and the liquid level can be detected accurately. Consumption can be reduced, and since superconducting materials have high electrical resistance, there is no need to increase sensitivity by using thin wires.In contrast to the conventional four-terminal method, a two-terminal method is sufficient and the mechanism is simpler. , it is possible to make a highly reliable liquid level gauge. Superconducting materials obtained by ultra-rapidly solidifying an alloy having the above composition from a molten state are shown in Table 1 below, and all of them have a superconducting transition of 4.2 to 5.0〓, which is approximately equal to the liquid helium temperature of 4.21〓. temperature, high normal conductivity resistance and good strength,
It is an amorphous single phase or a mixed phase with a crystalline phase containing at least 20% by volume of the amorphous phase, which has the ability to form a tape. One of the amorphous superconducting materials has a length of about 100 to 1000 mm, depending on the size of the liquid helium container.
A plate having a width of 0.1 to 5 mm and a plate thickness of 5 to 50 μm is used as a detection element.

【table】

[Table] Examples will be described below. Figure 1 shows a liquid level gauge based on the present invention, and Figure 2 shows the relationship between the length of a superconducting material with a composition of Zr ₈₀ Nb ₅ Al ₈ Si ₇ above the liquid helium surface and its electrical resistance. It is something that 1 is a container, 1a is a reference surface of the container, 2 is liquid helium, and 2a is a liquid level. 3 is a measuring device, 4 is a meter, 5 is an insulating material, 6 is a bolt integral with the insulating material, 7 is a rod, 7a is an upper support, and 7b is a lower end portion. 8 is a superconducting material, which has an upper end 8a and a lower end 8.
The intersection point 8c with the liquid surface 2a of liquid helium at point b is 8c. 9 is a support spring, 10 and 11 are lead wires,
11a, 11b are connected to a power source and a meter. Reference numeral 12 is a connecting wire that connects the superconducting material 8 and the lead wire 11, 13 is a low-temperature solder or silver paste, and 14 is an adhesive. 8d is lead wire 1
0 and the upper end 8a of the superconducting material 8, which is fixed with low temperature solder and adhesive like the lower end 8b and coincides with the reference surface 1a of the container 1. H is the distance between the liquid helium level and the above-mentioned 8d, and is a reference value representing the amount of liquid helium in the container. In the above configuration, if the lead wires 10 and 11 are energized, the electrical resistance of the superconducting material in liquid helium becomes 0, so the value displayed on the meter is the resistance of the distance H between the liquid level 2a and the superconducting material 8d. The distance of the liquid level from the reference surface of the container can be measured, and if the liquid helium increases or decreases, H increases or decreases and is displayed on the meter. The wire rod is supported substantially vertically over a portion of the total height of the helium container, and its length is 0.1 to 3.0 m. Furthermore, among the superconducting materials, the superconducting transition temperature is
In the case of 4.5 to 5.0〓, it is possible to generate Joule heat in the superconducting material using the lead wire and use it as the same as the superconducting material corresponding to 4.2〓. Even in this case, Joule heat is extremely small. It is. As described above, the present invention uses a superconducting material whose superconducting transition temperature matches the liquefaction temperature of liquid helium (4.2〓) as a liquid level detection element to measure the electrical resistance on the surface of liquid helium. It is a liquid level meter that can measure the helium liquid level and has a simple structure and is extremely reliable.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of a liquid level gauge according to the present invention.
A is a cross-sectional view from A to A, B is a cross-sectional view from B to B, and C is a partially broken enlarged view of part C. FIG. 2 is a graph showing the relationship between the length above the liquid helium surface and the electrical resistance of a superconducting material with a composition of Zr ₈₀ Nb ₅ Al ₈ Si ₇ .

Claims (1)

[Claims] 1 A superconducting alloy produced by ultra-rapid solidification from a liquid is represented by ZaMb(Q+Al)c, but in this formula, Z is one of Zr, Hf, or Ti, M is V,
One or more types of Nb, Q is Si, Ge
Consisting of one or both of the following, a is 10 to 90
atomic%, b is 80 atomic% or less, c is in the range of 10 to 25 atomic%, Q is 2 atomic% or more, and Al is 0.1 to 15 atomic%. Alloy containing Q+A composition in which a part of Al is replaced with 12 atomic % or less of any one or more of C, B, and Sn, and the volume percentage of the non-solid phase is 20%.
Among these superconducting alloys, alloys with a superconducting transition temperature of 4.2 to 5.0 K, which is approximately equal to the liquid helium temperature of 4.21〓, are used as electrical resistance wires, and the total height inside the liquid helium container is A liquid level gauge that measures the amount of liquid helium in a container by continuously measuring the superconducting region of the electrical resistance wire as an electrical resistance value, by vertically supporting a part over a length of 0.1 to 3.0 m.