Use of a High-Resolution Overview Spectrometer for the Visible Range in the TEXTOR Boundary Plasma

概要

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Passive spectroscopy is a standard diagnostic to observe the boundary layer of fusion plasmas. This method of visible spectroscopy is focused on the measurement of deuterium recycling flux and on the monitoring of impurity fluxes of O, He, etc., or W, C, etc., which result from erosion of plasma-facing components. In addition, ro-vibrational analysis of molecular transitions provides information about the molecular break-up in the plasma. Spectrometers used for studying the plasma boundary have to fulfill high demands with respect to the spectral, spatial, and time resolutions, the observable wavelength range, to the sensitivity and dynamic range of the detector in order to simultaneously observe and analyze the emission of both, atomic and molecular species present in the observed region. We present an overview spectrometer system that is able (a) to simultaneously measure strong atomic lines (e.g. Dα) and weak molecular bands (e.g. C2 Swan band), (b) to resolve narrow molecular lines (e.g. D2 Fulcher-α band) and allow their ro-vibrational analysis, and (c) to provide information about the spatial distribution in the plasma boundary. A full characterization of the custom-made system in a cross-dispersion arrangement with respect to resolving power, simultaneous wavelength coverage, sensitivity, etc., is presented. Examples of spectra (“footprints”) taken from an injection of C3H4 into TEXTOR are presented.