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The ASDEX Thomson scattering apparatus measures the scattered light of the laserbeam (l = 10640Å) in the near infrared to obtain density and temperature profiles. Furthermore this kind of apparatus can be used to analyse plasma radiation for determining radial Z(eff) profiles, as has been demonstrated at ASDEX for the first time. This method provides correct results, if the measured plasma radiation consists almost completely of bremsstrahlung. But besides bremsstrahlung the plasma emits recombination and line radiation. As shown by theoretical considerations, recombination radiation is negligible, but line radiation cannot be excluded. A spectral resolved measurement was therefore performed, which made it possible to choose those of the spectral measuring ranges of the Thomson scattering apparatus which are influenced least by line radiation. Furthermore, using the obtained results, it is possible to allow for the remaining line radiation, to give a radial profile of bremsstrahlung. This profile and the data of the Thomson scattering apparatus are used to determine Z(eff). The statistical errors are less than 10% in the plasma centre. There is a good agreement between Z(eff) profiles obtained by bremsstrahlung and the results of the charge exchange recombination spectroscopy.

Additional information

Authors: ENGELHARD M, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Report: IPP III/157 DE (1990) 73 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
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