ELECTRON-DENSITY SENSITIVE ULTRAVIOLET EMISSION-LINE RATIOS FOR CARBON-LIKE FE-XXI IN THE PLT TOKAMAK

Recent calculations of electron impact excitation rates in carbon-like Fc XXI are used to derive relative level populations and hence theoretical emission line ratios. These are compared with observed values measured from ultraviolet spectra of the Princeton Large Torus (PLT) tokamak, for which the electron density and temperature have been independently determined. Agreement between theory and observation is good, with typical discrepancies of 20% and differences of 4% for the best observed lines. This provides experimental support for the accuracy of the atomic data used in the line ratio calculations, and implies that they may be applied to the analysis of remote sources for which no independent N(e)-estimates exist, such as solar flares.