Production and measurement of high temperatures

The article is based mainly upon the study of thermally excited plasmas with temperatures in the range of 10 000-70 000°K. In case of no self-absorption the measurement of these temperatures can be effected by observation of lines or of continuous radiation emitted from the plasma. The study of lines implies both line intensities and line shapes. Following the discussion of the different methods of evaluating temperatures the specific properties of a plasma - viscosity, electrical and heat conductivity - are touched upon. Sections 2 to 6 deal with the production of high temperatures. Arcs, pulsed discharges and sparks, exploding wires and shock waves, and finally chemical reactions are discussed. The temperatures actually obtained, the practical applications, and the limitations of the different approaches are indicated. The writing of the article was completed early in 1957 but some of the most interesting results in the field of extremely high temperatures obtained during 1957 were added at the proof stage. The methods of temperature measurement presented here have been used frequently by many investigators and have proved to lead to reliable results of known accuracy in the temperature range below 10 5 deg K. It is expected that the same methods with minor alterations could be used in the region of temperatures exceeding 10 5 deg K.