Feasibility of alpha particle diagnostics for the active phase of JET, using Charge Exchange Recombination Spectroscopy

Observations of spectral emission from impurity ions in fusion plasmas following charge transfer from neutral deuterium or hydrogen beams has made great impact on deduction of impurity ion temperature, ion density and plasma rotation in recent years. In JET, transitions n→n' in the visible spectral region λ>3500 A are observed and the Do source is the neutral heating beam with primary particle energy in the range 40-80 keV/amu. The experimental arrangements, diagnostic methodology and deduction of the JET plasma behaviour have been reported previously. In this paper, attention is focussed specifically on He II(n=4-3) emission at λ=4686 A. (author) 8 refs., 5 figs