Investigation of helium flow impedance issues in the capillary based experimental cryostats Srinivasan K V1,*, Arolkar Vijay1, Swain Suvasis2, Jaison K A1 1Low Temperature Facility, Tata Institute of Fundamental Research, Mumbai, India 2Department of Nuclear and Atomic Physics, Tata Institute of Fundamental Research, Mumbai, India *E-mail ID: kvsrini@tifr.res.in
Online published on 4 December, 2023. The helium flow impedance is one of the hassles that occasionally occurs in the capillary-based experimental setups of commercial and homemade systems due to the choking of impurities in its fine capillary tubes, thus creating a problem with cooling below 4.2K. The capillary-based systems such as SQUID, PPMS, VSM, STM, and 4He VTI experience such clogging issues. Usually, this clogging is attributed to the trace amounts of hydrogen in the liquid helium. This clogging demands the warming up of the entire experimental system, followed by flushing and purging with high-purity helium gas to restore its normal performance. Despite warming up and cooling down, this clogging issue cannot be overcome entirely and gets repeated in a few days. Frequent warming up of the sensitive experimental setup having a superconducting magnet is a painful and laborious job, leading to cryostat downtime and the substantial quantity of expensive liquid helium in re-cooling it. The paper presents in-depth details on the detection techniques of hydrogen traces in the helium gas stream and the methodology adopted to rectify the helium-flow impedance issue cost-effectively, which has worked without the reoccurrence of capillary blockage issues since 2016. Top Keywords Liquid Helium, Flow Impedance, Capillary, Clogging, Hydrogen. Top |