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Low temperature refrigeration is one of the important factors restricting the large-scale application of HTS magnets. Helium/Neon are the scarce resource in the earth and expensive; The thermal stability of HTS magnets directly cooled by refrigerator is poor, and the electrical insulation under low vacuum is also poor. Liquid hydrogen/LNG are flammable and explosive, which may cause safety accidents; Liquid nitrogen has a high freezing point, and the electromagnetic properties of magnets at 65 K are limited; The thermal stability of HTS magnets cooled by solid nitrogen is also poor because of thermal separation of solid nitrogen and magnet, and the electromagnetic properties may also deteriorate after multiple cold and hot cycles. In order to solve above problems, a variety of binary and ternary liquid mixture are explored. The newly developed liquid nitrogen-carbon tetrafluoride mixed liquid media has a freezing point close to 60K at a molar ratio of 9:1, while the liquid nitrogen-liquid oxygen mixed liquid media has a freezing point close to 50K at a molar ratio of 2:8. It is of great significance to explore newer binary and ternary liquid mixtures in the 50K temperature zone or below. In this paper, recent progress concerning the liquid mixture-cooled HTS magnets and devices including superconducting energy pipeline (SEP), superconducting fault current limiter (SFCL) and superconducting magnets is presented with the emphasis focused on their electromagnetic characteristics and thermal stability compared with those devices cooled by other means.
