1) Cooling technology 
A Cryocooler is a standalone cooler, usually of table-top size. It is used to cool some particular application to cryogenic temperatures. A recent review is given by Radebaugh. The present article deals with various types cryocoolers and is partly based on a paper by De Waele. == Ideal heat exchangers and regenerators == Heat exchangers are import...
any of a variety of mechanically driven devices which use a fluid undergoing a thermodynamic cycle to provide cooling at cryogenic temperatures