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.