The Ar 17+ Ly 2 /ly 1 Ratio in Alcator C-mod Tokamak Plasmas the Ar 17+ Ly Α2 /ly Α1 Ratio in Alcator C-mod Tokamak Plasmas

Spectra of hydrogen-like Ar have been obtained from Alcator C-Mod tokamak plasmas using a spatially imaging high resolution x-ray spectrometer system. The ratio of Lyα2 (1S1/2 2P1/2) to Lyα1 (1S1/2 2P3/2) was found to be ∼ 0.52 regardless of plasma parameters, which is somewhat greater than the ratio of the statistical weights of the upper levels, 1/2. This difference is partially due to the effects of electron and ion collisional excitation of fine structure sub-levels. For the observations presented here, electron densities were in the range from 3×10/m to 4×10/m with electron and ion temperatures between 1 and 4 keV. Experimental results are compared to calculations from COLRAD, a collisional-radiative modeling code, with good agreement shown.