FUSION SPECTROSCOPY

This article traces developments in the spectroscopy of high temperatu re laboratory plasmas used in controlled fusion research from the earl y 1960's until the present. These three and a half decades have witnes sed many orders of magnitude increase in accessible plasma parameters such as density and temperature as well as particle and energy confine ment timescales. Driven by the need to interpret the radiation in term s of the local plasma parameters, the thrust of fusion spectroscopy ha s been to develop our understanding of (i) the atomic structure of hig hly ionised atoms, usually of impurities in the hydrogen isotope fuel; (ii) the atomic collision rates and their incorporation into ionizati on structure and emissivity models that take into account plasma pheno mena like plasma-wall interactions, particle transport and radiation p atterns; (iii) the diagnostic applications of spectroscopy aided by in creasingly sophisticated characterisation of the electron fluid. These topics are discussed in relation to toroidal magnetically confined pl asmas, particularly the Tokamak which appears to be the most promising approach to controlled fusion to date.