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Several experiments were conducted in ASDEX Upgrade to prove the suitability of tungsten as a divertor target material under the conditions of a high density and low temperature divertor. The observed fluxes from a tungsten tile into the plasma are low, in keeping with the extremely low sputtering yields. In addition, the very favourable effect of `prompt redeposition' (redeposition during the first gyration) could be confirmed by the experiments. Cooling of the edge region by neon injection seems permissible, i.e. neon impurity sputtering did not increase the eroded fluxes of tungsten. The transport and accumulation behaviour were investigated by means of the laser blow-off technique. No accumulation effects could be observed in ohmic discharges. In discharges with NBI heating but without ICRH, strong accumulation can occur. High heat flux tests were performed on graphite tiles coated with plasma sprayed tungsten, which withstood a thermal load of 15 MW/m2 lasting 2 s as well as 1000 cycles of 10 MW/m2 for 2 s without disabling damage. Owing to the encouraging results, an experiment using a tungsten divertor is planned in ASDEX Upgrade

In this work EBIT measurements in the spectral range of 4–7 nm with electron energies from 0.7 keV to 4 keV are compared in detail with tokamak spectra from ASDEX Upgrade. The energy and temperature dependence of spectral lines and features are investigated and an identification of the charge states W39+–W45+ for spectral lines between 4.5 nm and 6.5 nm is possible by taking cross sections from atomic data produced by plane-wave Born calculations via the Cowan code. In the range 12–14 nm the identification of spectral lines emitted by tungsten is improved even though no EBIT measurements are available, as special tokamak discharges have provided ideal possibilities for analysis. These discharges show spectra which are dominated by the emissions from a small region with a narrow electron temperature range. Therefore, only very few ion states contribute to the emission in contrast to the usual case where in the tokamak spectra the emissions of a larger number of ion states are superimposed. Tokamak spectra for varying electron temperature are also used to investigate the correlation to EBIT spectra for the quasicontinuum feature at 5 nm which is emitted by ion states W27+–W35+. We conclude that the narrower features in the EBIT spectra at a certain electron beam energy result from the smaller number of coexisting ion states.