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

G.A. Swaaij, van, K.E. Bystrov, D. Borodin, A. Kirschner, L.B. Vegt, van der, G.J. Rooij, van, G.C. De Temmerman, W.J. Goedheer

Research output: Contribution to journalArticleAcademicpeer-review

15 Citations (Scopus)

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¿–X 2¿ Gerö 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 Te <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 ne = 1.3 × 1020 m-3, to 2.8 at ne = 9.3 × 1020 m-3. Its inclusion significantly improved agreement between experiment and modeling.
Original languageEnglish
Article number095013
Pages (from-to)095013-1/9
Number of pages9
JournalPlasma Physics and Controlled Fusion
Volume54
Issue number9
DOIs
Publication statusPublished - 2012

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