Liquid helium level sensors on a PCB carrier with integrated temperature reading

Abstract A flexible liquid helium level gauge has been developed to compensate the lack of commercial availability to procure replacement level gauges for the LHC 1.8 K refrigeration unit cold box requiring an active measurement length of about 1 m. The main difficulty for manufacturing the level gauges is related to the insertion capillary requiring an overall length ranging from 1.75 m to 4.30 m. The liquid helium level gauge is based on a NbTi superconducting wire attached to a PCB (Prototype Circuit Board) carrier including two surface mounted heating resistors and a Cernox ™ temperature sensor at the bottom tip of the gauge. The paper presents the design requirements, the main basic components, and the manufacturing steps of the superconducting liquid helium level gauge. Experimental data is also presented demonstrating the correct operation of the proposed novel gauges.