X-ray and extreme ultraviolet spectroscopy on DIII-D

Two spectrometers were installed to measure tungsten emission in the core of DIII-D plasmas during a metal rings experimental campaign. The spectral range of the high-resolution (1340 spectral channels), variable-ruled grating X-ray and Extreme Ultraviolet Spectrometer (XEUS) extends from 10–71 A-dot . The spectral range of the second spectrometer, the Long-Wavelength Extreme Ultraviolet Spectrometer (LoWEUS), measures between 31–174 A-dot . Three groups of tungsten lines were identified with XEUS: W³⁸⁺-W⁴⁵⁺ from 47–63 A-dot , W²⁷⁺-W³⁵⁺ from 45–55 A-dot , and W²⁸⁺-W³³⁺ from 16–30 A-dot . Emission lines from tungsten charge states W²⁸⁺, W⁴³⁺, W⁴⁴⁺, and W⁴⁵⁺ are identified and the line amplitude is presented versus time. Peak emission of W⁴³⁺-W⁴⁵⁺ occurs between core T_e =2.5-3 keV, and peak emission of W²⁸⁺ occurs at core T_e ≤ 1.3 keV. One group of tungsten lines, W⁴⁰⁺-W⁴⁵⁺, between 120–140 A-dot , was identified with LoWEUS. W⁴³⁺-W⁴⁵⁺ lines measured with LoWEUS track the sawtooth cycle. Sensitivity to the sawtooth cycle and the correlation of the peak emission with core electron temperature show that these spectrometers track the on-axis tungsten emission of DIII-D plasmas.