AGOTADO - New Cryocooler-Based Helium Liquefaction and Purification Techniques : from Recovered Gas to Ultra-Pure Liquid

The purpose of this thesis is to present the development of an emerging technology for small-scale helium recovery, focusing in all the needed steps: helium recovery, helium purification and helium liquefaction. This technology uses cryocoolers for both, the liquefaction and the purification, in a novel way: the gas is simply in direct thermal contact with the cryocooler, and, the process takes advantage smartly of the outstanding helium properties. The technology is efficient, modular and scalable, making feasible the installation in almost any facility, from very small size (e.g. average helium consumption less than 1 L/day), to medium size (e.g. 200 L/day). Finally, we present the ultra-pure liquid helium concept “Clean Helium” (hydrogen-free liquid helium) that has been produced with the technology presented here. “Clean Helium” solves a global issue: The blocking of fine capillary tubes used as flow impedances in 4He evaporation cryostats to achieve temperatures below 4.2 K.