Inter-ELM pedestal evolution in low triangularity JET-ILW discharges

H. R. Wilson, C. Bowman, S. C. Cowley, I. Cziegler, D. Dickinson, L. Frassinetti, K. Gibson, C. Ham, L. Horvath, A. Kirk, B. Lipschultz, A. E.L. Lunniss, C. F. Maggi, C. M. Roach, S. Saarelma, P. B. Snyder, A. Thornton, A. Wynn

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Studies of the pedestal stability in low triangularity, d=0.2, JET ITER-Like Wall discharges are presented, following the evolution between ELMs. The pressure gradient tracks the ideal MHD ballooning threshold, only lagging behind it when the threshold rises rapidly as the plasma penetrates the second stability region. This is consistent with a role for the kinetic ballooning mode in the pedestal structure. When the plasma has second stability access, e.g. for low gas puff discharges, the peeling-ballooning mode is marginally stable at ELM onset. In cases where there is no second stability access the discharges are some way short of the peeling-ballooning threshold, so this alone cannot be the trigger for the ELM. A low amplitude sinusoidal oscillation in the Be-II emission is observed that correlates well with the ELMs, and has an associated high frequency magnetic field fluctuation, ~100-250kHz, with modulated amplitude. This might be associated with a new filamentary equilibrium state.

Original languageEnglish (US)
Title of host publication44th EPS Conference on Plasma Physics, EPS 2017
EditorsA. Bret, M. Fajardo, E. Westerhof, A. Melzer, B. Dromey, C. Riconda
PublisherEuropean Physical Society (EPS)
ISBN (Print)9781510849303
StatePublished - Jan 1 2017
Externally publishedYes
Event44th European Physical Society Conference on Plasma Physics, EPS 2017 - Belfast, United Kingdom
Duration: Jun 26 2017Jun 30 2017

Publication series

Name44th EPS Conference on Plasma Physics, EPS 2017

Other

Other44th European Physical Society Conference on Plasma Physics, EPS 2017
CountryUnited Kingdom
CityBelfast
Period6/26/176/30/17

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics

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