Noble Gases as Favorite Coolants for Joule-Thomson Cryostats

Abstract

B-Z. May talRafael Institute Cryogenic Section Haifa 31021, Israel Thennodynamic features of noble gases make them superior, in many senses, over the others, as a coolant in Ioule-Thomson (IT) cryostats. This is demonstrated by comparisons of the following relevant parameters: isenthalpic and isothennal integral IT effects, (~T)H' (~Hh, cool down range (until reaching liquefaction at nozzle's outlet), (~T)CD' nonnal boiling temperature, T BOIL , portion of liquefaction, in addition to the desirable lack of toxicity and flammability. As a result, the comparison points to krypton (Kr) to be preferred over the commonly used Freon 14 (CF 4 ), Xenon (Xe) seems to be the better alternative for first stage, high ambient temperature IT cryocooling.