Laboratory freezer appliance

A laboratory freezer appliance providing a usable storage space on the order of 5 to 20 cubic feet capable of storage temperatures of -160 DEG C. and lower including an insulated freezer chamber, heat transfer tubes in proximity to the freezer chamber carrying liquid argon at ultra-low temperatures which absorbs heat from the freezer chamber thereby vaporizing the argon in the heat transfer tubes; a closed cycle, hermetically-sealed free piston Stirling cycle heat pump providing a cold end above a vertical displacer driven by a linearly reciprocating piston at a delta T to the freezer chamber of about -13 DEG C.; a condensing chamber surrounding the cold end of the heat pump for condensing argon vapor to the argon liquid; and a distributor for distributing liquid argon from the condensing chamber to the heat transfer tubes and returning argon vapor to the condensing chamber, all without mechanical pumping of the argon, in a continuous, closed cycle refrigeration system.