A Review of Charge-Exchange Spectroscopy and Applications to Fusion Plasmas

The use of charge-exchange spectroscopy as a diagnostic tool in fusion plasmas is steadily growing. This technique exploits spectral lines produced by charge transfer from hydrogen atoms into highly excited states of impurity ions. The concentrations and transport properties of the dominant, fully ionized low- Z impurities can, therefore, be measured. In addition, it is possible to observe transitions having wavelengths long enough for obtaining accurate Doppler shifts and widths, even in plasmas with temperatures of several keV, and ion temperatures and plasma rotation are increasingly being determined from such spectral lines. In this paper, the atomic physics considerations, including the influence of the plasma environment, are reviewed, and several recent examples of applications to plasma problems are summarized.