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Chemical erosion measurements in tokamaks by spectroscopy

Brezinsek, S; Pospieszczyk, A; Kirschner, A; Sergienko, G; Huber, A; Philipps, V; ... JET-EFDA Contributors,; + view all (2004) Chemical erosion measurements in tokamaks by spectroscopy. PHYS SCRIPTA , T111 42 - 48.

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Abstract

The paper focusses on the conversion of photon fluxes into particle fluxes by means of photon efficiencies in tokamaks. Both flux contributions to the chemical erosion yield, the deuterium flux, as well as the eroded hydrocarbon flux, are critically investigated, and possible uncertainties in the data evaluation are identified. Inverse photon efficiencies, so-called S/XB or D/XB values, are critical factors in the conversion of the fluxes. For deuterium, the flux determination is influenced by the presence of a molecular source. In contrast, the hydrocarbon flux is also uncertain due to the indirect conversion from photon to particle fluxes. In particular, the conversion of CD photon fluxes into CD4 particle fluxes can lead to misinterpretation, because C2Dy and CD4 can finally contribute to the flux of CD radicals. A correction formula for the total hydrocarbon flux which includes the contribution of different hydrocarbon sources is introduced.We also present results from spectra simulations of the A-X transition of CD, which show that the usual observation of the CD band (429.4 nm 430.9 nm) may lead to an underestimation of the total photon flux from the whole A-X transition of more than a factor of two. Up to now, the modelling with erosion and deposition codes only takes the complete electronic transition into account. A unification of the quantities is necessary to compare modelling and experiment.

Type:Article
Title:Chemical erosion measurements in tokamaks by spectroscopy
Keywords:PLASMA-WALL INTERACTIONS, DIII-D, ASDEX UPGRADE, DIVERTOR, FLUXES, CH4/CD4, YIELDS, ITER
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology

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