Development and Validation of an Indirect Heating Type Superconducting Level Sensors for Liquid Helium Storage System

For a cryogen, the liquid level is one of the crucial parameters among pressure, temperature etc. Therefore, measurement of liquid level is one of the fundamental interests related to cryogenic systems’ operation. A minimum cryogen level should be maintained in the container before filling it with a new batch of cryogen and preventing the thermal quench of superconducting equipment like superconducting magnets. The level of the liquid inside the container is generally expressed as a percentage of the total volume. An indirect heating type level sensor was designed and developed to determine the liquid level inside a helium dewar in this work. The NbTi superconducting wire was used to measure the liquid level, and Manganin wire was used to heat the portion of the wire so that the portion of the sensing element above the liquid level is maintained in the normal state. The measurement of the resistance and the voltage drop across the wire is correlated with the actual liquid level. This paper presents the development of indirect heating type superconducting level sensors for liquid helium storage dewars and a suitable readout circuit with the digital display of the liquid level.