Dynamics of edge localized modes in the TCV tokamak

Degeling, A. W.; Martin, Yves; Bak, P.; Lister, J.B.; Llobet, X.

doi:10.1088/0741-3335/43/12/304

Cited by 28 publications

(50 citation statements)

References 22 publications

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“…In magnetically confined fusion plasmas, edge localized modes (ELMs; see the top left panel of figure 1), whose characteristics are deeply linked to the overall confinement properties of the plasma, provide a well-defined dataset of pulsed events. The statistical properties of measured ELM sequences [7,27,28] should provide a rich field of research, shedding fresh quantitative light on plasma confinement. However, ELM measurements are challenging insofar as magnetically confined fusion plasmas are seldom quasistationary on timescales long enough to enable robust ELM statistics to be constructed.…”

Section: Statistics Of Pulsed Phenomena In Plasmasmentioning

confidence: 99%

Characterization and interpretation of strongly nonlinear phenomena in fusion, space and astrophysical plasmas

Dendy

Chapman

2006

Plasma Phys. Control. Fusion

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Much of plasma behaviour is governed by multiple distinct nonlinear processes, operating on a wide range of lengthscales and timescales, that are coupled together in innumerable feedback loops. Capturing and quantifying this nonlinear behaviour is crucial at all levels of description, ranging from individual events to global phenomenology. In recent years, a range of techniques derived from complex systems science has been applied successfully to nonlinear plasma datasets. The present paper reviews several of these techniques in the context of applications spanning fusion, space, solar and astrophysical plasmas. Topics include non-Gaussian probability density functions, notably extreme event distributions in fusion and astrophysics and power law distributions in the solar context; differencing and rescaling of fluctuation data, which has yielded information on the number of dominant plasma turbulent processes, and the spatiotemporal ranges over which they operate, in plasmas ranging from microquasar accretion discs to L-mode and dithering H-mode fusion plasmas in the MAST tokamak; quantitative measures of mutual information content and pattern repetition between causally linked but spatiotemporally separated nonlinear events in solar wind and magnetospheric plasmas; global statistics of full-disc solar irradiance; and ELMing, considered as a sequence of pulsed events, in H-mode fusion plasmas in the JET tokamak. These developments in nonlinear plasma data characterization provide fresh additional insights into the underlying plasma physics. They also provide new opportunities for comparing models with data, and with each other, and open avenues for the development of a more rigorous predictive capability in this field.

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Section: Statistics Of Pulsed Phenomena In Plasmasmentioning

confidence: 99%

Characterization and interpretation of strongly nonlinear phenomena in fusion, space and astrophysical plasmas

Dendy

Chapman

2006

Plasma Phys. Control. Fusion

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“…Characterization of the dynamics of ELMing processes via their quantitative statistical signatures is relatively novel. [8][9][10] It may also be informative to quantify, as here, the statistical signatures of correlation between ELMs and signals that capture global plasma dynamics.…”

Section: Introductionmentioning

confidence: 99%

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

et al. 2014

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A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM.

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“…Quantitative characterization of the dynamics of ELMing processes via their time domain properties, such as inter-ELM time intervals and ELM event waiting times, is relatively novel [10][11][12][13][14][15] and has provided evidence of unexpected structure in the sequence of ELM occurrence times. Recently, 16,17 we found that the signals from a system scale diagnostic, the toroidally integrating full flux loops in the divertor region of JET, contain statistically significant information on the occurrence times of intrinsic ELMs: the ELMs tend to preferentially occur when the full flux loop signals are at a specific analytic phase of their timeseries.…”

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The global build-up to intrinsic edge localized mode bursts seen in divertor full flux loops in JET

et al. 2015

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A global signature of the build-up to an intrinsic edge localized mode (ELM) is found in the temporal analytic phase of signals measured in full flux azimuthal loops in the divertor region of JET. Toroidally integrating, full flux loop signals provide a global measurement proportional to the voltage induced by changes in poloidal magnetic flux; they are electromagnetically induced by the dynamics of spatially integrated current density. We perform direct time-domain analysis of the high time-resolution full flux loop signals VLD2 and VLD3. We analyze plasmas where a steady H-mode is sustained over several seconds during which all the observed ELMs are intrinsic; there is no deliberate intent to pace the ELMing process by external means. ELM occurrence times are determined from the Be II emission at the divertor. We previously [Chapman et al., Phys. Plasmas 21, 062302 (2014); Chapman et al., in 41st EPS Conference on Plasma Physics, Europhysics Conference Abstracts (European Physical Society, 2014), Vol. 38F, ISBN 2-914771-90-8] found that the occurrence times of intrinsic ELMs correlate with specific temporal analytic phases of the VLD2 and VLD3 signals. Here, we investigate how the VLD2 and VLD3 temporal analytic phases vary with time in advance of the ELM occurrence time. We identify a build-up to the ELM in which the VLD2 and VLD3 signals progressively align to the temporal analytic phase at which ELMs preferentially occur, on a ∼2−5ms timescale. At the same time, the VLD2 and VLD3 signals become temporally phase synchronized with each other, consistent with the emergence of coherent global dynamics in the integrated current density. In a plasma that remains close to a global magnetic equilibrium, this can reflect bulk displacement or motion of the plasma. This build-up signature to an intrinsic ELM can be extracted from a time interval of data that does not extend beyond the ELM occurrence time, so that these full flux loop signals could assist in ELM prediction or mitigation.

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Dynamics of edge localized modes in the TCV tokamak

Cited by 28 publications

References 22 publications

Characterization and interpretation of strongly nonlinear phenomena in fusion, space and astrophysical plasmas

Characterization and interpretation of strongly nonlinear phenomena in fusion, space and astrophysical plasmas

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

The global build-up to intrinsic edge localized mode bursts seen in divertor full flux loops in JET

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