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An ASDEX neutral pressure gauge was modified in such a way that it delivers not only the global density of neutral particles (molecules and atoms) by ionisation, but also the density of the atoms by measurement of the Lyman-alpha radiation produced by electron impact excitation. Owing to the very weak intensity the main effort was dedicated to developing a detector-filter combination which allows the Lyman-alpha radiation to be separated from the H(2) bands in the VUV and be measured with a time resolution of at least a few ms. Several versions were tested theoretically and practically. The best solution was found to be a combination of an O(2) filter using MgF(2) windows and a multichannel plate. The arrangement was tested and calibrated with an atomic beam of known intensity from an oven..

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Authors: LÖRCHER M, Max-Planck-Institut für Plasmaphysik, Garching bei München (DE);LORCHER M, Max-Planck-Institut fur Plasmaphysik, Garching bei Munchen (DE)
Bibliographic Reference: Report: IPP III/156 DE (1990) 65 pp.
Availability: Available from Max-Planck-Institut für Plasmaphysik, 8046 Garching bei München (DE)
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