Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus

A.J. Webster, J. Morris, T.N. Todd, S. Brezinsek, P. Coad, J. Likonen, M. Rubel, JET EFDA Contributors

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

A unique sequence of 120 almost identical plasmas in the Joint European Torus (JET) recently provided two orders of magnitude more statistically equivalent data than ever previously available. The purpose was to study movement of eroded plasma-facing material from JET's new Beryllium wall, but it has allowed the statistical detection of otherwise unobservable phenomenon. This includes a sequence of resonant-like waiting times between edge-localised plasma instabilities (ELMs), instabilities that must be mitigated or avoided in large magnetically confined plasmas such as those planned for ITER. Here, we investigate the cause of this phenomenon, using the unprecedented quantity of data to produce a detailed picture of the plasma's behaviour. After combining the data, oscillations are clearly observable in the plasma's vertical position, in edge losses of ions, and in Beryllium II (527?nm) light emissions. The oscillations are unexpected, are not obvious in data from a single pulse alone, and are all clearly correlated with each other. They are likely to be caused by a small vertical oscillation that the plasma control system is not reacting to prevent, but a more complex explanation is possible. The clearly observable but unexpected link between small changes in the plasma's position and changes to edge-plasma transport and stability suggest that these characteristics cannot always be studied in isolation. It also suggests new opportunities for ELM mitigation and control that may exist.
Original languageEnglish
Article number082501
JournalPhysics of Plasmas
Volume22
Issue number8
DOIs
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed

Fingerprint

Joint European Torus
cycles
beryllium
oscillations
plasma control
magnetohydrodynamic stability
light emission
isolation
causes
pulses

Keywords

  • JET
  • ELM

Cite this

Webster, A. J., Morris, J., Todd, T. N., Brezinsek, S., Coad, P., Likonen, J., ... Contributors, JET. EFDA. (2015). Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus. Physics of Plasmas, 22(8), [082501]. https://doi.org/10.1063/1.4927755
Webster, A.J. ; Morris, J. ; Todd, T.N. ; Brezinsek, S. ; Coad, P. ; Likonen, J. ; Rubel, M. ; Contributors, JET EFDA. / Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus. In: Physics of Plasmas. 2015 ; Vol. 22, No. 8.
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abstract = "A unique sequence of 120 almost identical plasmas in the Joint European Torus (JET) recently provided two orders of magnitude more statistically equivalent data than ever previously available. The purpose was to study movement of eroded plasma-facing material from JET's new Beryllium wall, but it has allowed the statistical detection of otherwise unobservable phenomenon. This includes a sequence of resonant-like waiting times between edge-localised plasma instabilities (ELMs), instabilities that must be mitigated or avoided in large magnetically confined plasmas such as those planned for ITER. Here, we investigate the cause of this phenomenon, using the unprecedented quantity of data to produce a detailed picture of the plasma's behaviour. After combining the data, oscillations are clearly observable in the plasma's vertical position, in edge losses of ions, and in Beryllium II (527?nm) light emissions. The oscillations are unexpected, are not obvious in data from a single pulse alone, and are all clearly correlated with each other. They are likely to be caused by a small vertical oscillation that the plasma control system is not reacting to prevent, but a more complex explanation is possible. The clearly observable but unexpected link between small changes in the plasma's position and changes to edge-plasma transport and stability suggest that these characteristics cannot always be studied in isolation. It also suggests new opportunities for ELM mitigation and control that may exist.",
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Webster, AJ, Morris, J, Todd, TN, Brezinsek, S, Coad, P, Likonen, J, Rubel, M & Contributors, JETEFDA 2015, 'Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus', Physics of Plasmas, vol. 22, no. 8, 082501. https://doi.org/10.1063/1.4927755

Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus. / Webster, A.J.; Morris, J.; Todd, T.N.; Brezinsek, S.; Coad, P.; Likonen, J.; Rubel, M.; Contributors, JET EFDA.

In: Physics of Plasmas, Vol. 22, No. 8, 082501, 2015.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus

AU - Webster, A.J.

AU - Morris, J.

AU - Todd, T.N.

AU - Brezinsek, S.

AU - Coad, P.

AU - Likonen, J.

AU - Rubel, M.

AU - Contributors, JET EFDA

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PY - 2015

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AB - A unique sequence of 120 almost identical plasmas in the Joint European Torus (JET) recently provided two orders of magnitude more statistically equivalent data than ever previously available. The purpose was to study movement of eroded plasma-facing material from JET's new Beryllium wall, but it has allowed the statistical detection of otherwise unobservable phenomenon. This includes a sequence of resonant-like waiting times between edge-localised plasma instabilities (ELMs), instabilities that must be mitigated or avoided in large magnetically confined plasmas such as those planned for ITER. Here, we investigate the cause of this phenomenon, using the unprecedented quantity of data to produce a detailed picture of the plasma's behaviour. After combining the data, oscillations are clearly observable in the plasma's vertical position, in edge losses of ions, and in Beryllium II (527?nm) light emissions. The oscillations are unexpected, are not obvious in data from a single pulse alone, and are all clearly correlated with each other. They are likely to be caused by a small vertical oscillation that the plasma control system is not reacting to prevent, but a more complex explanation is possible. The clearly observable but unexpected link between small changes in the plasma's position and changes to edge-plasma transport and stability suggest that these characteristics cannot always be studied in isolation. It also suggests new opportunities for ELM mitigation and control that may exist.

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KW - ELM

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DO - 10.1063/1.4927755

M3 - Article

VL - 22

JO - Physics of Plasmas

JF - Physics of Plasmas

SN - 1527-2419

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