High-resolution tungsten spectroscopy relevant to the diagnostic of high-temperature tokamak plasmas

Abstract

The x-ray transitions in Cu- and Ni-like tungsten ions in the 5.19--5.26 \AA{} wavelength range that are relevant as a high-temperature tokamak diagnostic, in particular for JET in the ITER-like wall configuration, have been studied. Tungsten spectra were measured at the upgraded Shanghai- Electron Beam Ion Trap operated with electron-beam energies from 3.16 to 4.55 keV. High-resolution measurements were performed by means of a flat Si 111 crystal spectrometer equipped by a CCD camera. The experimental wavelengths were determined with an accuracy of 0.3--0.4 m\AA{}. The wavelength of the ground-state transition in Cu-like tungsten from the $3{p}^{5}3{d}^{10}4s4d\phantom{\rule{4pt}{0ex}}[{(3/2,{(1/2,5/2)}_{2}]}_{1/2}$ level was measured. All measured wavelengths were compared with those measured from JET ITER-like wall plasmas and with other experiments and various theoretical predictions including cowan, relac, multiconfigurational Dirac-Fock (MCDF), and fac calculations. To obtain a higher accuracy from theoretical predictions, the MCDF calculations were extended by taking into account correlation effects (configuration-interaction approach). It was found that such an extension brings the calculations closer to the experimental values in comparison with other calculations.