Experimental evaluation of fractional abundance data for W23+–W28+

Based on the electron temperature (T e) dependence of 20 forbidden tungsten line intensities observed in several Large Helical Device discharges, we experimentally evaluated fractional abundance profiles for highly charged tungsten ions (W) in the charge states 23–28. Although the absolute values of the fractional abundance are still inaccessible in our method, relative profiles against T e values were evaluated. The T e values at the profile peak for q = 23, 24, 25, 26, 27 and 28 states tungsten abundance were evaluated as 0.53, 0.58, 0.65, 0.78, 0.93, and 1.14 keV, respectively. These results were ≈20% smaller than those reported by Putterich et al (2008 Plasma Phys. Control. Fusion 50 085016), which are the theoretical calculations adjusted to match the quasi-continuum emission by 24–35 tungsten ions measured in the extreme ultraviolet region, and ≈60% larger than the pure theoretical calculation by Sasaki et al (2013 J. Phys. B: At. Mol. Opt. Phys. 46 175701).