Modeling of Carbon Migration During JET Injection Experiments
Authors: J.D. Strachan, J. Likonen, P. Coad, M. Rubel, A. Widdowson, M. Airila, P. Andrew, S.Brezinsek, G. Corrigan, H.G. Esser, S. Jachmich, A. Kallenbach, A. Kirschner, A. Kreter, G.F. Matthews, V.Philipps, R.A. Pitts, J. Spence, M. Stamp, S. Wiesen, and JET-EFDA contributors
Abstract:
JET has performed two dedicated carbon migration experiments on the final run day of separate campaigns (2001 and 2004) using 13CH4 methane injected into repeated discharges. The EDGE2D/NIMBUS code modelled the carbon migration in both experiments. This paper describes this modelling and identifies a number of important migration pathways: 1. deposition and erosion near the injection location, 2. migration through the main chamber SOL, 3. migration through the private flux region aided by E×B drifts, and 4. neutral migration originating near the strike points. In H-Mode, type I ELMs are calculated to influence the migration by enhancing erosion during the ELM peak and increasing the longrange migration immediately following the ELM. The erosion/re-deposition cycle along the outer target leads to a multistep migration of 13C towards the separatrix which is called “walking”. This walking created carbon neutrals at the outer strike point and led to 13C deposition in the private flux region. Although several migration pathways have been identified, quantitative analyses are hindered by experimental uncertainty in divertor leakage, and the lack of measurements at locations such as gaps and shadowed regions.
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Accepted to: Journal of Nuclear Fusion (May 2008)
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Download PPPL-4359 (pdf 1.6MB 43pp)
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