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

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 proceeding › Conference contribution › peer-review

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 language	English
Title of host publication	44th EPS Conference on Plasma Physics, EPS 2017
Editors	A. Bret, M. Fajardo, E. Westerhof, A. Melzer, B. Dromey, C. Riconda
Publisher	European Physical Society (EPS)
ISBN (Print)	9781510849303
State	Published - 2017
Externally published	Yes
Event	44th European Physical Society Conference on Plasma Physics, EPS 2017 - Belfast, United Kingdom Duration: Jun 26 2017 → Jun 30 2017

Publication series

Name	44th EPS Conference on Plasma Physics, EPS 2017

Conference

Conference	44th European Physical Society Conference on Plasma Physics, EPS 2017
Country/Territory	United Kingdom
City	Belfast
Period	06/26/17 → 06/30/17

Funding

Acknowledgements: Work performed within the framework of the EUROfusion Consortium and received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. We acknowledge support from EPSRC grants EP/L01663X/1 & EP/K504178/1, funding the EPSRC Centre for Doctoral Training in the Science and Technology of Fusion Energy. The authors acknowledge access to the EUROfusion High Performance Computer (Marconi-Fusion) through EUROfusion and to the ARCHER computing service through the Plasma HEC Consortium EPSRC grant number EP/L000237/1. Wilson and Lipschultz have been funded in part by the Wolfson Foundation and UK Royal Society through a Royal Society Wolfson Research Merit Award.

Funders	Funder number
UK Royal Society
H2020 Euratom	633053
Engineering and Physical Sciences Research Council	EP/K504178/1, EP/L01663X/1
Royal Society
Wolfson Foundation
EPSRC Centre for Doctoral Training in Medical Imaging	EP/L000237/1

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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Wilson, H. R., Bowman, C., Cowley, S. C., Cziegler, I., Dickinson, D., Frassinetti, L., Gibson, K., Ham, C., Horvath, L., Kirk, A., Lipschultz, B., Lunniss, A. E. L., Maggi, C. F., Roach, C. M., Saarelma, S., Snyder, P. B., Thornton, A., & Wynn, A. (2017). Inter-ELM pedestal evolution in low triangularity JET-ILW discharges. In A. Bret, M. Fajardo, E. Westerhof, A. Melzer, B. Dromey, & C. Riconda (Eds.), 44th EPS Conference on Plasma Physics, EPS 2017 Article P2.112 (44th EPS Conference on Plasma Physics, EPS 2017). European Physical Society (EPS).

@inproceedings{7341384ede57480d8f5d5df01918acb4,

title = "Inter-ELM pedestal evolution in low triangularity JET-ILW discharges",

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.",

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

note = "Publisher Copyright: {\textcopyright} 2017 IOP Publishing Ltd.; 44th European Physical Society Conference on Plasma Physics, EPS 2017 ; Conference date: 26-06-2017 Through 30-06-2017",

year = "2017",

language = "English",

isbn = "9781510849303",

series = "44th EPS Conference on Plasma Physics, EPS 2017",

publisher = "European Physical Society (EPS)",

editor = "A. Bret and M. Fajardo and E. Westerhof and A. Melzer and B. Dromey and C. Riconda",

booktitle = "44th EPS Conference on Plasma Physics, EPS 2017",

}

Wilson, HR, Bowman, C, Cowley, SC, Cziegler, I, Dickinson, D, Frassinetti, L, Gibson, K, Ham, C, Horvath, L, Kirk, A, Lipschultz, B, Lunniss, AEL, Maggi, CF, Roach, CM, Saarelma, S, Snyder, PB, Thornton, A & Wynn, A 2017, Inter-ELM pedestal evolution in low triangularity JET-ILW discharges. in A Bret, M Fajardo, E Westerhof, A Melzer, B Dromey & C Riconda (eds), 44th EPS Conference on Plasma Physics, EPS 2017., P2.112, 44th EPS Conference on Plasma Physics, EPS 2017, European Physical Society (EPS), 44th European Physical Society Conference on Plasma Physics, EPS 2017, Belfast, United Kingdom, 06/26/17.

Inter-ELM pedestal evolution in low triangularity JET-ILW discharges. / Wilson, H. R.; Bowman, C.; Cowley, S. C. et al.
44th EPS Conference on Plasma Physics, EPS 2017. ed. / A. Bret; M. Fajardo; E. Westerhof; A. Melzer; B. Dromey; C. Riconda. European Physical Society (EPS), 2017. P2.112 (44th EPS Conference on Plasma Physics, EPS 2017).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

TY - GEN

T1 - Inter-ELM pedestal evolution in low triangularity JET-ILW discharges

AU - Wilson, H. R.

AU - Bowman, C.

AU - Cowley, S. C.

AU - Cziegler, I.

AU - Dickinson, D.

AU - Frassinetti, L.

AU - Gibson, K.

AU - Ham, C.

AU - Horvath, L.

AU - Kirk, A.

AU - Lipschultz, B.

AU - Lunniss, A. E.L.

AU - Maggi, C. F.

AU - Roach, C. M.

AU - Saarelma, S.

AU - Snyder, P. B.

AU - Thornton, A.

AU - Wynn, A.

PY - 2017

Y1 - 2017

N2 - 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.

AB - 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.

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M3 - Conference contribution

AN - SCOPUS:85055043767

SN - 9781510849303

T3 - 44th EPS Conference on Plasma Physics, EPS 2017

BT - 44th EPS Conference on Plasma Physics, EPS 2017

A2 - Bret, A.

A2 - Fajardo, M.

A2 - Westerhof, E.

A2 - Melzer, A.

A2 - Dromey, B.

A2 - Riconda, C.

PB - European Physical Society (EPS)

T2 - 44th European Physical Society Conference on Plasma Physics, EPS 2017

Y2 - 26 June 2017 through 30 June 2017

ER -

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

Abstract

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