Performance analysis of a NbTi level sensor while filling LHe into a cryostat

A mathematical model for simulating the operation of the superconducting level sensor inside a cryostat was developed earlier which was experimentally validated using NbTi and MgB2 level sensors in LHe. It was observed that the operation of these sensors is highly dependent on heat transfer phenomenon in the vapor phase inside the cryostat. As the condition of vapor phase and consequently the heat transfer phenomenon changes during different stages of cryostat operation, such as filling, normal operation, operation during high heat in-leak and draining, etc., it is important to investigate the sensor operation during the same. Hence, the operation of NbTi level sensor under different liquid boil-off conditions was studied earlier. The present article discusses the operation of NbTi sensor while filling LHe into a cryostat. It was observed that both one-current and heating current-measuring current (two-current) method provide accurate level measurement, with later having better linearity for voltage versus liquid level curve.