Experimental Study on Superconducting Level Sensors in Liquid Helium

An approach for experimental investigation of the optimum sensor current of a superconducting level sensor is established and is then used for the investigation of the same of a NbTi and a MgB2/SS level sensors in liquid helium. On comparing the experimental results with that of the computational model established earlier, to simulate the operation of a superconducting level sensor, it was found that both agree closely. This shows the validity of the computational model for the characterization of a superconducting level sensor. Further on, the operation of these level sensors in a two-current method was studied. The results showed a higher heat load and level measurement time. However, it indicated an opportunity of retaining the linearity of the voltage versus liquid level curve even under high boil-off rate inside the cryostat. To scrutinize these findings, the NbTi level sensor operation in liquid helium was studied up to a boil-off rate of 5.77 g/s. It was observed that the sensor operation was not affected; however, the two-current method showed a more accurate level measurement compared to the one-current method.