Dissociative recombination and electron-impact de-excitation in CH photon emission under ITER divertor-relevant plasma conditions

TitleDissociative recombination and electron-impact de-excitation in CH photon emission under ITER divertor-relevant plasma conditions
Publication TypeJournal Article
Year of Publication2012
AuthorsG.A van Swaaij, K. Bystrov, D. Borodin, A. Kirschner, L.B van der Vegt, G.J van Rooij, G. De Temmerman, W.J Goedheer
JournalPlasma Physics and Controlled Fusion
Volume54
Issue9
Pagination095013
Date PublishedSep
Type of ArticleArticle
ISBN Number0741-3335
KeywordsCARLO CODE ERO, CHEMICAL EROSION, HYDROCARBON INJECTION, LOW-TEMPERATURE, METHANE PLASMA, RADICALS, SIMULATION, SPECTROSCOPY, TOKAMAKS, TRANSPORT
Abstract

For understanding carbon erosion and redeposition in nuclear fusion devices, it is important to understand the transport and chemical break-up of hydrocarbon molecules in edge plasmas, often diagnosed by emission of the CH A(2)Delta-X-2 Pi Gero band around 430 nm. The CH A-level can be excited either by electron-impact (EI) or by dissociative recombination (DR) of hydrocarbon ions. These processes were included in the 3D Monte Carlo impurity transport code ERO. A series of methane injection experiments was performed in the high-density, low-temperature linear plasma generator Pilot-PSI, and simulated emission intensity profiles were benchmarked against these experiments. It was confirmed that excitation by DR dominates at T-e < 1.5 eV. The results indicate that the fraction of DR events that lead to a CH radical in the A-level and consequent photon emission is at least 10%. Additionally, quenching of the excited CH radicals by EI de-excitation was included in the modeling. This quenching is shown to be significant: depending on the electron density, it reduces the effective CH emission by a factor of 1.4 at n(e) = 1.3 x 10(20) m(-3), to 2.8 at n(e) = 9.3 x 10(20) m(-3). Its inclusion significantly improved agreement between experiment and modeling.

URLhttp://arxiv.org/abs/1207.0736
DOI10.1088/0741-3335/54/9/095013
Division

PSI

Department

CPP-LT

PIDc68f3accf7051fafe52626054fea10de
Alternate TitlePlasma Phys. Control. Fusion
LabelOA
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