Spektroskopische Untersuchung der Strahlungsrekombination im Divertor von ASDEX Upgrade

With the development of a fusion reactor the investigation of the interaction between the hot plasma and the wall is one of the most important tasks. The solution of the wall erosion problem due to high power and particle flux from the plasma onto the divertor target is a major challenge. Detached plasmas appear to be favourable with respect to a reduced plasma wall interaction. These plasmas are dominated by three-body recombination. Because of the strong volume recombination the plasma flux is replaced by an isotropic neutral flux. Thus, the power entering the divertor target is spread onto a large area, and hence the plasma wall interaction is reduced substantially. The strong recombination radiation was used for the analyses of spectroscopic methods for the determination of electron temperature and electron density. Thus it was possible to investigate a high density and low temperature plasma regime which cannot be explored with standard diagnostic methods. Both line and continuum radiation were used for the determination of the plasma parameters electron density and temperature. It was found that under the simplified assumptions of homogeneous distributions along the lines of sight the used spectroscopic methods for the temperature determination do not yield the same result. Temperatures derived from the Boltzmann plot are significantly lower than those obtained from the Balmer sprung method. The explanation for this is the inhomogeneity of the divertor plasma and the line-of-sight integration of measured intensities. The inclusion of theoretical models like B2-EIRENE which describe the spatial distribution of plasma parameters in the scrape off layer enabled the quantitative comparison of the methods on the basis of realistic plasma profiles along the lines of sight. (orig.)Available from TIB Hannover: RA 71(10/15) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman