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A 3 He/ 4 He dilution refrigerator is a cryogenic device that provides continuous cooling to temperatures as low as 2 mK, with no moving parts in the low-temperature region. [ 1 ] [ 2 ] The cooling power is provided by the heat of mixing of the helium-3 and helium-4 isotopes.
A helium-3 refrigerator is a simple device used in experimental physics for obtaining temperatures down to about 0.2 kelvins.By evaporative cooling of helium-4 (the more common isotope of helium), a 1-K pot liquefies a small amount of helium-3 in a small vessel called a helium-3 pot.
Equal mixtures of liquid 3 He and 4 He below 0.8 K separate into two immiscible phases due to differences in quantum statistics: 4 He atoms are bosons while 3 He atoms are fermions. [8] Dilution refrigerators take advantage of the immiscibility of these two isotopes to achieve temperatures of a few milli kelvin .
But the 3 He must be condensed to a liquid first, and a 1-K pot is typically used for this purpose. Another example is a dilution refrigerator, where a mixture of 3 He and 4 He forms a phase boundary in a mixing chamber and can cool down to a few millikelvins. Dilution refrigerators typically use a 1-K pot to condense the 3 He/ 4 He mixture.
The Einstein–Szilard or Einstein refrigerator is an absorption refrigerator which has no moving parts, operates at constant pressure, and requires only a heat source to operate. It was jointly invented in 1926 by Albert Einstein and his former student Leó Szilárd , who patented it in the U.S. on November 11, 1930 ( U.S. patent 1,781,541 ).
Evaporative cooling of ordinary helium forms a 1-K pot, which can cool to at least 1.2 K. Evaporative cooling of helium-3 can provide temperatures below 300 mK. These techniques can be used to make cryocoolers, or as components of lower-temperature cryostats such as dilution refrigerators. As the temperature decreases, the vapor pressure of the ...