Insertion thermometry experience at CERN

Abstract Insertion thermometry is desirable for low pressure gaseous cold helium environment due to the poor heat transfer coefficient between the fluid and the pipe wall, complicating the measurement on the insulation vacuum side. Insertion thermometry requires a capillary that, in the case of CERN equipment, has a wide variation of the overall length. Furthermore, the capillary is prone to inner pipe restrictions due to inappropriate bending or welding joints. The main advantage of insertion instrumentation is the exchangeability of damaged sensors; however, its installation can be extremely difficult in presence of restrictions and it is not trivial to ensure that the temperature sensor location reaches the end of the capillary inside the cold fluid’s vessel. This paper presents two approaches developed at CERN, they are based on either a sufficiently rigid stainless-steel wire with centering beads or a PCB carrier.