Development of lab scale sub-cooled liquid nitrogen facility for high temperature superconductor applications

The technological advances in high temperature superconductors (HTS) have led to its use in various high voltage and high current applications. HTS based devices have huge application prospect compared to low temperature superconductors (LTS) owing to their higher engineering current density, higher critical temperature (hence higher operating temperature) resulting in high power density and lower investment on cryogenics. Here we report the development of sub-cooled liquid nitrogen facility for cooling small scale HTS application with single phase liquid nitrogen under a temperature range of 64 K – 77 K. We have sub-cooled liquid nitrogen inside commercially available 50 L Dewar by boiling nitrogen under reduced pressure. As a proof of principle, we have cooled a 1 meter long vacuum insulated flexible cryogenic transfer line to 70 K using sub-cooled nitrogen. This same facility can be used to efficiently cool future High Temperature Superconductor (HTS) based applications at a laboratory scale.