Lake Shore 4 K CCR Series Cryostats

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Two-stage Gifford-McMahon (G-M) refrigerator systems have been in widespread use for several decades. Room temperature helium gas is first compressed and then supplied to the refrigerator via flexible gas lines. The compressed helium is cooled by expansion and provides cooling to two heat stations on the refrigerator. After cooling the refrigerator, the gas is returned to the compressor to repeat the cycle.

Pulse tube (PT) refrigerator systems use a similar compression/expansion cycle but eliminate the moving regenerator found in G-M cryocoolers. PT cryocoolers often have reduced vibration levels at the vacuum interface flange as compared with G-M systems.

Is a 4 K cryocooler economically practical?

Prior to the introduction of 4 K cryocoolers, liquid helium was most commonly used to cool equipment and experiments to 4 K. The following chart shows the operating cost of a typical liquid helium-cooled apparatus (not including storage Dewar evaporative losses). In some cases, the entire cost of a 4 K refrigerator can be recovered in the first year!