Helium circulation cooling experiment for a 3T NbTi superconducting magnet

Abstract

This paper proposes an experimental investigation to validate the use of helium as the sole coolant in a pipe circulation cooling mode for a small 3 T NbTi superconducting magnet. Injecting helium into pipes and liquefying the magnet at 4.2 K will also be explored, utilizing the evaporation of small amounts of liquid helium within the pipes to cool the NbTi magnet and calculate its liquefaction volume and cooling time. Firstly, we investigated a novel approach to achieve acceptable temperatures for current leads by augmenting the top mass and increasing the length of the leads. Additionally, stainless steel (SS) loop tubes surrounding the magnet were designed in a new way to enhance convective heat exchange. Finally, various heat conduction devices were added and after successfully cooling all parts of the experimental apparatus, the heat transfer formula will be used to calculate the theoretical cooling time of pulsed supplementary helium gas, which will then be compared and discussed with actual experimental time. The cryogenic experiment shows that less liquid helium without any other coolants can be adopted efficiently to cool LTS magnets by SS pipelines. Consequently, this approach is significant to reducing consumption of coolant for cooling the LTS NbTi magnet to 4.2 K.