The progress of cryogenic engineering and the role of refrigerators are described. Small refrigerators, mostly for electronics application, are coming to be standardized, while large refrigerators have a trend to become multipurpose. For future applications of cryogenic equipments and devices, the development and cost of refrigeration by refrigerators will become the most important factor.
Working principle and theoretical thermodynamic efficiency of refrigeration cycles with regenerator which have been developed for practical use or have a prospective application are described. Six refrigeration cycles, namely Kirk cycle, Vuilleumier cycle, Gifford-MacMahon cycle, Higa cycle, Pulse tube refrigerator and Vortex tube are included. The last one is not practically used as a refrigeration cycle at present, but it would be worth while to describe it as one of the possible lines of consideration for future refrigeration cycles. Most of the cycles can be extended to a cascade cycle of two or three stages to realize lower refrigeration temperature, but it is not described here to avoid complexity.
Several methods of refrigeration are available to attain the temperature below one degree Kelvin. These methods utilize adiabatic demagnetization of paramagnetic salts, adiabatic magnetization of superconductors, a Helium three refrigerator and a Helium three-Helium four mixing or dilution refrigerator. The principles and the combination of these refrigeration methods are discussed. Other methods such as the refrigeration using mechano-caloric effect of Helium II, a Helium three expansion engine which produces cold due to the work done against the osmotic pressure and an adiabatic compression method of Helium three are also reviewed.
Recently the demand for large-scale refrigerators and liquefiers has been increased, both for experimental and industrial uses. In construction of such plants the following specifications have to be taken account of; high thermodynamic efficiency, long maintenance-free operating time, high reliability, low operating-cost, and so on. Modern techniques, developing-problems and fields application of the use of large-scale refrigerators and liquefiers are described.
Helium refrigerator for superconducting magnet is described. The magnet can be cooled down by minimum liquid helium requirements may with precooling procedure. Several wayes for combining the magnet with commercially designed refrigerators are given in this paper.
Hydrogen bubble chambers and those refrigerators The requirements for the refrigerators in high energy physics, especially for the hydrogen bubble chamber refrigerators are discussed. Major hydrogen bubble chambers and those refrigerators in Western Europe and USA are classified according to the types of refrigeration system. Most of those refrigerators are belonging to the type of conservative one. A design concept on the bubble chamber refrigerator which couples an excellent liquefier to an advanced chamber by means of a large liquid hydrogen tank is proposed. Other refrigerators for the superconducting magnets, the liquefied hydrogen target and the polarized target are also discussed.