Fokker-Planck simulations of the Tokamak Fusion Test Reactor (TFTR) energetic ion mode discharges were performed to evaluate the utility of deriving the central ion temperature Ti from deuterium neutral beam charge exchange spectra above the neutral beam injection energy. The Ti values obtained from fitting the calculated spectra obtained from sightlines nearly tangent to the neutral beam injection radius reproduce the central ion temperature within ±10% over the full range of TFTR energetic ion mode parameters. The code simulations demonstrate that the ion temperature obtained from the high energy tangential deuterium charge exchange spectrum is insensitive to variations in plasma density, Zeff, plasma current, loop voltage, and injected neutral beam power and energy. The use of this method to reduce charge exchange data from TFTR energetic ion mode plasmas is demonstrated.
Charge-exchange spectra near the injection energy in tokamaks equipped with tangential neutral beams – experiment and theory