Tungsten spectroscopy relevant to the diagnostics of ITER divertor plasmas

The possibility of using extreme ultraviolet emission from low charge states of tungsten ions to diagnose the divertor plasmas of the ITER tokamak has been investigated. Spectral modelling of Lu-like W3+ to Gd-like W10+ has been performed by using the Flexible Atomic Code, and spectroscopic measurements have been conducted at the Sustained Spheromak Physics Experiment (SSPX) in Livermore. To simulate ITER divertor plasmas, tungsten was introduced into the SSPX spheromak by prefilling it with tungsten hexacarbonyl prior to the usual hydrogen gas injection and initiation of the plasma discharge. The tungsten emission was studied using a grazing-incidence spectrometer.