Present situation of temperature measurement by means of platinum resistance thermometers below 0°C is described. After a short note on available equipment, the method of representating the relationship between the resistance and thermodynamic temperature is dealt with. Above the triple point of hydrogen, the extension of the International Practical Temperature Scale below 90°K and its improvement above 90°K are referred to, and a method of obtaining the temperature from a reference table such as CCT-64 and calibration at several thermometric fixed points, which has been proposed at the Comité Consultatif de Thermométrie, is described. Below the triple point of hydrogen down to helium temperatures, the resistance-temperature relationship of platinum is discussed.
Pulse Tube Refrigeration is a new refrigeration method which was conceived by W. E. Gifford in 1961. This refrigerator can make a low temperature without any mechanical devices, actually, a temperature of 26°K has already been achieved with a LN2 cooling single stage refrigerator and a 43°K with 4 stage refrigerator. The interest in the method is due to the fact that, though the phenomenon is very complex and difficult to analyze, the equipment of a Pulse Tube Refrigerator can be very small and simple. The notes that have been assembled here try to give a basic understanding of the surface heat pumping mechanism, its characteristics, advantages and limitations. These should provide enough information for making a decision regarding the development of Pulse Tube Refrigerator.