Pedestal particle balance studies in JET-ILW H-mode plasmas

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Plasma Physics and Controlled Fusion, Volume 65, issue 4
JET-ILW type I ELMy H-modes at 2.5 MA/2.8 T with constant NBI heating (23 MW) and gas fuelling rate were performed, utilising edge localised mode (ELM) pacing by vertical kicks and plasma shaping (triangularity, δ) as tools to disentangle the effects of ELMs, inter-ELM transport and edge stability on the pedestal particle balance. In agreement with previous studies, the pedestal confinement improves with increasing δ, mostly due to a significant increase in pedestal density while the ELM frequency ( f E L M ) is decreased. Improved pedestal confinement with increasing δ was observed even when the pedestal MHD stability was degraded artificially by vertical kicks, implying that increased triangularity may favourably affect the inter-ELM pedestal recovery. The workflow developed to quantify the pedestal particle balance uses high time-resolution profile reflectometry to characterise the inter-ELM evolution of the plasma particle content ( d N / d t ), the NEO drift-kinetic solver to evaluate the neoclassical fluxes and interpretative EDGE2D-EIRENE simulations to estimate the edge particle source. The edge particle source is then constrained by deuterium Balmer-α line intensity measurements in the main chamber, which are, however, strongly affected by reflections from the metal walls. The reflections are accounted for by the CHERAB code taking the divertor emission (the brightest light source in the torus) distribution from imaging spectroscopy measurements as input. Our analysis shows that in the second half of the ELM cycle, the volume-integrated particle source is larger than d N / d t , indicating that transport plays a key role in the inter-ELM pedestal recovery.
Funding Information: The first author would like to thank A Chankin for fruitful discussions. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion) and from the EPSRC [Grant Number EP/W006839/1]. To obtain further information on the data and models underlying this paper please contact . Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. Publisher Copyright: © 2023 Crown copyright. Reproduced with the permission of the Controller of Her Majesty’s Stationery Office
EDGE2D-EIRENE, EIRENE, fuelling, H-mode, JET-ILW, particle transport, pedestal
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Horvath, L, Lomanowski, B, Karhunen, J, Maslov, M, Schneider, P A, Simpson, J, Brix, M, Chapman-Oplopoiou, B, Corrigan, G, Frassinetti, L, Groth, M, Lawson, K, Maggi, C F, Menmuir, S, Morales, R B, Moulton, D, Myatra, O, Nina, D, Pereira, T, Réfy, D I, Saarelma, S, Vécsei, M & JET Contributors 2023, ' Pedestal particle balance studies in JET-ILW H-mode plasmas ', Plasma Physics and Controlled Fusion, vol. 65, no. 4, 044003 .