Abstract
We fabricated a superconducting level sensor with a magnesium-diboride wire and carried out experiments with liquid hydrogen. First, we observed a normal zone propagation phenomenon in the gaseous hydrogen. We also measured the terminal voltage of the sensor with a constant current depending on the relative change in the liquid level, and recognized that input power during normal operation must be suppressed to realize a level sensor for liquid hydrogen. Operation of the level sensor was numerically simulated based on the experimental results. The time evolution of temperature distribution along the wire was calculated using a heat balance equation including the cooling effects of liquid hydrogen and vaporized gas. The influences of wire size and material properties on minimum propagating current and power consumption in the gaseous hydrogen were evaluated to achieve the optimum design for the level sensor.
