Spectroscopic measurements of tokamak plasma ion temperature using Doppler broadening of impurity lines : correction for chordal line-of-sight observations

Tokamak ion temperatures measured using the Doppler-broadened impurity spectral line technique are usually underestimated because the line intensity is integrated along chordal lines of sight and is assumed to be the intensity at the chordal distance from the center of the plasma (radial distance). An analytical correction of the ion temperature radial profile during a series of reproducible discharges on the Tokamak de Varennes reveals a 10%–20% underestimation at the plasma center. The lines used are Ne IX (1248.2 Å) and O VII (1623.7 Å). Reconstruction of spectral line intensities and shapes using measured electron temperature and density profiles, ion density radial profiles simulated by a plasma impurity transport code, and published atomic data can verify and predict this correction.