cryogenic equipment

INSTALLATION WITH DILUTION REFRIGERATOR ³Не в ⁴Не FOR OPERATE IN 0.028-4.2К RANGE

To investigate the properties of condensed media at low temperatures, one usually needs a refrigerator that ensures stationary temperatures over a wide range, from 0.01 to 4.2 K, at high cooling power. Such investigations can be carried out using, as separate techniques, an evaporation refrigerator with ^ЗНе (HelioxTMTL, Top loading ³He system), [1,2] для работы при 0.4 -3 К, or ⁴Не, and the ³Не / ⁴Не dilution refrigerator "Kelvinox®TLM, Top-loading into liquid dilution refrigerator" [3]. The common feature of the given devices is the use of the same hot fluid both for obtaining a low temperature and for cooling the sample under investigation. A refrigerator containing both the evaporation (with ³Не or ⁴Не) and dilution (³Не in ⁴Не) cooling cycles is described. The heat connection between two cooling cycles is through a heat exchanger between the ³Не - ⁴Не dilution chamber and the helium collector. The device allows both simultaneous and separate use of the evaporation and dilution cooling cycles, since it has two independent circulation circuits. Using the evaporation cycle, the region above 0.75 K can be reached which is inaccessible using dilution alone. In the joint mode, i.e. when both the evaporation and dilution cycles are in use, the total cooling power of the refrigerator at 0.4< T <0.75 K can be much higher than the cooling power of the ³Не - ⁴Не. If one uses dilution of 3He in 4He for cooling a mixture of ³Не and ⁴Не, isotopes of arbitrary composition condense in the collector. The present refrigerator allows one to study the temperature dependence of the heat gain to the dilution chamber caused by recondensing of a superfluid film and the heat conduction of the gas in the collector evacuation line. The lowest temperature achieved in the ³Не / ⁴Не dilution mode is 28mK.

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