Towards understanding reactor relevant tokamak pedestals

C. Ham, Arkaprava Bokshi, D Brunetti, Guillermo Bustos Ramírez, B Chapman, J. W. Connor, David Dickinson, A R Field, L Frassinetti, A Gillgren, J. P. Graves, T P Kiviniemi, S Leerink, B. McMillan, Sarah Newton, S. Pamela, C. M. Roach, S. Saarelma, J Simpson, S F SmithE R Solano, P Strand, A J Virtanen, JET contributors

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The physics of the tokamak pedestal is still not fully understood, for example there
is no fully predictive model for the pedestal height and width. However, the pedestal is key
in determining the fusion power for a given scenario. If we can improve our understanding
of reactor relevant pedestals we will improve our confidence in designing potential fusion
power plants. Work has been carried out as part of a collaboration on reactor relevant pedestal
physics. We report some of the results in detail here and review some of the wider work which
will be reported in full elsewhere. First, we attempt to use a gyrokinetic-based calculation
to eliminate the pedestal top density as a model input for Europed/EPED pedestal predictions.
We assume power balance at the top of the pedestal, that is, the heat flux crossing the separatrix
must be equal to the heat source at the top of the pedestal and investigate the consequences
of this assumption. Unfortunately, this method was not successful. Second, we investigate
the effects of non flux surface density on the bootstrap current. Third, type I ELMs will not
be tolerable for a reactor relevant regime due to the damage that they are expected to cause
to plasma facing components. In recent years various methods of running tokamak plasmas
without large ELMs have been developed. These include small and no ELM regimes, the use
of resonant magnetic perturbations and the use of vertical kicks. We discuss the quiescent
H-mode here. Finally we give a summary and directions for future work.
Original languageEnglish
Article number096013
Number of pages17
JournalNuclear Fusion
Publication statusPublished - 2 Aug 2021

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