earticle

영어

Most sub-Kelvin refrigerators have been developed to meet the rigorous demands of scientific inquiry. These advanced cooling devices include sorption-based evaporation cooler, Helium3-Helium4 dilution refrigerators, and adiabatic demagnetization refrigerators (ADRs), each of which utilizes fundamental principles such as evaporation cooling, phase separation, and the magnetocaloric effect. Recently, sub-Kelvin cooling has gained significant attention beyond the realm of pure scientific research, driven by the needs of quantum sensing, communication, and computing technologies. This paper describes an innovative singleshot DR (Dilution Refrigerator) system assisted by ADR as a precooler. Primary objective of this development is to minimize the Helium3 inventory without requiring cryogenic heat exchangers, while optimizing thermodynamic efficiency through careful selection of the temperature ranges for ADR and DR operations. Computer simulations, based on the assumption of thermodynamic equilibrium, demonstrate the straightforward operation of the proposed refrigerator with minimal Helium3 usage under various operating conditions For the prototype DR, initial temperatures for the still and mixing chamber are set at 0.6 K and 0.7 K, with a mixture ratio of 40 % Helium3. The Helium3-Helium4 mixture is obtained through the condensation process facilitated by the continuous adiabatic demagnetization refrigerator (CADR), using GGG (Gadolinium Gallium Garnet) as the magnetic refrigerant. The simulation results could predict the conditions for terminating the DR operation. It is anticipated that the mixing chamber can achieve temperatures below approximately 0.2 K, provided the liquid helium meniscus in the still is maintained and the interface between the concentrated and diluted helium is sustained within the mixing chamber throughout the sorption pumping.