Figure 3.

Temperature vs time curves recorded during (a) cooling down and (b) warming up the liquefier cold head and (c) swapping the receiving and refilling dewars. The temperature discontinuities in the warming-up curve, indicated by the arrows, correspond to the phase change temperatures of hydrogen (14 and 20 K), nitrogen (63 and 77 K), and water (273 K). The small bump in the cooling-down curve (indicated by the arrow) marks the moment when all He vapor loads are connected to the recovery system, signaling the system’s entering into its fully functional status.