Abstract
We are currently developing an external-heating-type superconducting magnesium diboride (MgB2) level sensor for a liquid hydrogen tank. The heating effect of an external heater on an 800-mm-long MgB2 level sensor was previously reported. However, the heating effect of an external heater on the MgB2 level sensor has not yet been clarified in the case of changing the sensor length. In this study, we examined the temperature distribution and level-detecting characteristics of a 200- mm-long MgB2 level sensor. It was found that the temperature of the sensor above the liquid surface was higher than Tc at a heater input of 6 W or more. Regarding the level-detecting characteristics of the MgB2 sensor, the linear correlation coefficient was 0.99 or more at a heater input of 3 W and above. Moreover, the ratio of the effective level-detecting length to the total length remained constant at a heater input of 6 W or more. Similar results were observed for different sensor lengths. Therefore, the optimum heater input was 6 W regardless of the sensor length.
