Contributions to Fusion Research from Studies of Foil-Excited Heavy Ion Beams

Abstract

XUV spectra in the wavelength region from 5-55 nm have been measured at Brookhaven National Laboratory for foil-excited ion beams of Au, W, Zr, Mo, Fe, and Ti. These atoms are of particular interest in fusion research. In sharp contrast to the wide-ranging time-dependent charge state evolution of heavy ions in a plasma discharge, foil excitation of a heavy ion beam produces relatively well-defined narrow charge-state distributions. Existing accelerators, such as the Brookhaven MP tandems, can produce sufficiently energetic heavy ion beams to span the range of charge states found in present-day tokamaks. The comparison of spectra from beam-foil excitation and tokamak plasmas can therefore be used to infer the average ion and charge state makeup of the plasma discharge. Such comparisons with Au, W, and Mo features in tokamak spectra are discussed and spectra for Zr and Fe (which are expected contaminants in new tokamaks) are presented. Additional contributions to fusion research from beam-foil experiments are demonstrated. These include: wavelengths and identifications for lines which can be resolved in plasma spectra and direct determinations of radiative lifetimes and absorption oscillator strengths for these transitions which are used to determine impurity concentrations in plasmas.