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The mean ionic charge Z(eff) is one of the chief parameters for description of fusion plasmas. For known electron densities and temperatures Z(eff) can be determined from the measured intensity of Bremsstrahlung emitted by the plasma, but the presence of spectral lines within the range of wavelengths chosen for measurement of the continuum often hinders and falsifies measurement. It is therefore necessary to establish the existence of a suitable range free of spectral lines by means of spectrally resolved measurement and to monitor this range throughout continuum measurement for any appearance of spectral lines. The near infra-red range (NIR) offers the best chances for continuum measurement due to the low line density expected in it. This paper is an introduction to hardware and software for NIR spectroscopy and Z(eff) diagnostics in W7-AS. It should serve as a manual for carrying out diagnostics and - after some practice has been gained - for analysing measurement data. The Z(eff) diagnostics described have so far produced good results in W7-AS and are certainly worth keeping as a standard diagnostic method for this experiment.

Additional information

Authors: MANDL W, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE)
Bibliographic Reference: Report: IPP III/201 DE (1995) 19 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
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