MgB2 Superconducting Wire for Liquid Hydrogen Level Sensing
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Solution Overview
Problem
MgB2-based superconducting liquid hydrogen fluid level sensors face accuracy issues due to the unimmersed portion becoming superconducting, leading to incorrect measurements, as it is cooled by thermal conduction, and heating this portion to maintain accuracy results in evaporative loss and complexity.
Innovation Solution
An MgB2-based superconducting wire with a critical temperature of 20-25 K is developed, using a composition of Mg, B, and Al in a molar ratio of 1:1.8-2.2:0.05-0.25, and a wire diameter of at most 1.0 mm, which reduces the transition width to at most 5 K, allowing for accurate measurements without heating the unimmersed portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the unimmersed portion is cooled by thermal conduction, then the measurement accuracy deteriorates because the unimmersed portion becomes superconducting, but heating the unimmersed portion causes evaporative loss and increases system complexity
Solution Approach 1:
The patent changes the critical temperature parameter of the superconducting material from the conventional 39K (MgB2) to a lower range of 25K-35K by adding aluminum elements. This parameter change allows the unimmersed portion to remain non-superconducting at temperatures above the liquid hydrogen boiling point (20K) without requiring active heating, thereby eliminating the heating system complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent creates different thermal conditions for different portions of the sensing element. The immersed portion is cooled to 20K and becomes superconducting, while the unimmersed portion remains at a higher temperature (25K-35K) and stays in a normal resistive state. This local quality differentiation enables accurate level measurement without requiring a heating system for the unimmersed portion.
2Measurement precision
If the unimmersed portion is heated to prevent superconductivity, then measurement accuracy is maintained, but evaporative loss increases
Solution Approach 1:
By changing the critical temperature parameter to 25K-35K through aluminum addition, the patent eliminates the need for heating the unimmersed portion. The unimmersed portion naturally remains in a normal state at temperatures between 25K-35K, which are above the liquid hydrogen boiling point of 20K but below the superconducting transition temperature. This prevents evaporative loss while maintaining measurement accuracy.
Solution Approach 2:
The patent converts the potentially harmful thermal conduction that cools the unimmersed portion into a beneficial effect. Instead of viewing the cooling as a problem requiring heating compensation, the lower critical temperature design allows the unimmersed portion to naturally operate in the normal resistive state due to ambient thermal conditions, turning the cooling effect into a feature that eliminates evaporative loss.
3Measurement precision
If a heater is added to the unimmersed portion to maintain temperature above critical temperature, then measurement accuracy is improved, but the system becomes more complex
Solution Approach 1:
The patent fundamentally changes the critical temperature parameter from 39K to 25K-35K by incorporating aluminum elements into the MgB2 structure. This parameter change eliminates the need for heating devices, as the unimmersed portion naturally operates below the critical temperature in normal ambient conditions, thereby simplifying the sensing element structure while maintaining measurement accuracy.
Solution Approach 2:
The patent extracts and eliminates the heating system from the sensing element structure. By designing the superconducting material with a lower critical temperature (25K-35K), the heating function is completely removed, leaving only the essential sensing components. This extraction simplifies the overall device structure and reduces maintenance requirements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables accurate measurement of liquid hydrogen levels without heating the unimmersed portion, reducing evaporative loss and simplifying the measurement system, while maintaining high accuracy and reliability.
Implementation Method 1
MgB2, which is a new superconductor which was discovered in Japan in 2001, has a critical temperature of 39 K. Therefore, it can exhibit superconductivity in liquid hydrogen, which has a boiling point of approximately 20 K under atmospheric pressure.
Implementation Method 2
the unimmersed portion is unavoidably cooled by liquid hydrogen due to thermal conduction, and its temperature near the immersed portion approaches 20 K, which is the boiling point of liquid hydrogen
Data Source
AI summary
An MgB2-based superconducting wire for a liquid hydrogen fluid level sensor which can maintain an unimmersed portion of the MgB2-based superconducting wire for a liquid hydrogen fluid level sensor in a non-superconducting state even without heating the unimmersed portion is provided. A wire for a liquid hydrogen fluid level sensor comprises an MgB2-based superconductor which contains Mg, B, and Al. The critical temperature at which the electrical resistance becomes essentially zero is 20-25 K, and the transition width, which is the difference between the temperature at which the electrical resistance begins to decrease toward zero and the critical temperature, is at most 5 K.