Relating to a branch of Physics involving the production and effects of very low temperatures.  Example; a cryogenic pump: typically a pump with two stages, one refrigerated to about 80 K and a second to about 15 K.  The first pumps non- permanent gases (primarily, water-vapour and carbon dioxide), the second stage pumps Nitrogen and Oxygen.  Although Hydrogen and Helium are not condensed, they are trapped within a cold matrix absorber.