Greifswald 2009 – scientific programme

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P: Fachverband Plasmaphysik

P 15: Poster: Diagnostik

P 15.7: Poster

Wednesday, April 1, 2009, 17:30–19:30, Foyer des IfP

A maximum entropy based Abel inversion for bolometer measurements on WEGA — •Daihong Zhang, Heinrich Laqua, Matthias Otte, Louis Giannone, and Stefan Marsen — Max-Planck-Institut fuer Plasmaphysik, Teilinstitut Greifswald, EURATOM Association, Wendelsteinstr.1, 17491 Greifswald, Germany

Maximum-entropy based Abel inversion is applied for reconstructing the radial radiation profiles in the WEGA stellarator, where a multi-channel bolometer system is installed. The inversion procedure has been tested by forward calculations of presumed radiation profiles, taking the realistic geometries of the individual view channels into account. After exact reproduction of the input profiles, Gaussian-noise is added to the line-integrated signals of each channel, in order to check the sensitivity of the inversed results to errors in the raw signals. The contribution presents detailed results of this analysis.

The inversion method has been used for data processing of the WEGA bolometer system, which has become a standard diagnostic tool for measuring the radiation distributions. As, in the WEGA plasmas, the radiation is mainly contributed by the working gas itself, the radiation distribution reflects the profiles of the plasma parameters. Thus, the bolometer has the potential of providing additional information on the plasma pressure profile reflecting the power deposition of the ECR-heating. Recently, strongly peaked radiation profiles were observed in over-dense plasmas heated by electron Bernstein waves (EBWs). This is believed to be attributed to a centrally peaked power deposition of the EBWs heating. Results in this regard are discussed.