Thermoelectric currents and their role during ELM formation in JET

Rack, M.; Wingen, A.; Liang, Y.; Spatschek, K. H.; Harting, D.; Devaux, S.; Contributors, Jet‐Efda

doi:10.1088/0029-5515/52/7/074012

Cited by 10 publications

(13 citation statements)

References 31 publications

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“…The thermoelectric current model [29] describes the nonlinear evolution of an ELM. Its application for DIII-D and JET [6,28] shows good agreement with measurements. The model is based on the concept that an initial heat pulse triggers thermoelectric currents, through short connection length flux tubes [30].…”

Section: Interpretation Based On the Thermoelectric Current Modelsupporting

confidence: 55%

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Findings of pre-ELM structures through the observation of divertor heat load patterns at JET with appliedn= 2 perturbation fields

Rack¹,

Sieglin²,

Eich³

et al. 2014

Nucl. Fusion

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Resonant magnetic perturbation experiments at JET with the ITER-like wall have shown the formation of radially propagating pre-ELM structures in the heat flux profile on the outer divertor. These appear a few milliseconds before the major divertor heat load, caused by type-I edge-localized modes (ELMs). The formation of the pre-ELM structures is accompanied by an increase in the Dα emission. For some pronounced examples, the propagation appears to end at the positions where an increased heat load is seen during the ELM crash a few milliseconds later. These observations are presented and discussed along with a comparison of a thermoelectric edge currents model.

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Section: Interpretation Based On the Thermoelectric Current Modelsupporting

confidence: 55%

“…This demonstrates the dynamic nature of the observed structures. It has been reported that additional thermoelectric currents in the plasma edge during the onset of an ELM can lead to the formation of such dynamic footprint patterns [6,28].…”

Section: Pre-elm Structures Versus Radially Propagating Elm Filamentsmentioning

confidence: 99%

Findings of pre-ELM structures through the observation of divertor heat load patterns at JET with appliedn= 2 perturbation fields

Rack¹,

Sieglin²,

Eich³

et al. 2014

Nucl. Fusion

Self Cite

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“…As will be discussed in the next subsection, the ergodization does not need to be produced by current carrying filaments since it can be produced by the magnetic fluctuations associated with the ballooning mode itself. In the case of current carrying filaments, these currents are either thermoelectric in nature, localized by intrinsic error fields [62,63], or due to the dynamo effect [64]. These models find that the plasma edge can be ergodized, and manifold structures form, when localized currents of 200-300 A are present.…”

Section: The Role Of Ergodizationmentioning

confidence: 99%

Recent progress in understanding the processes underlying the triggering of and energy loss associated with type I ELMs

et al. 2014

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The type I ELMy H-mode is the baseline operating scenario for ITER. While it is known that the type I ELM ultimately results from the peeling-ballooning instability, there is growing experimental evidence that a mode grows up before the ELM crash that may modify the edge plasma, which then leads to the ELM event due to the peeling-ballooning mode. The triggered mode results in the release of a large number of particles and energy from the core plasma but the precise mechanism by which these losses occur is still not fully understood and hence makes predictions for future devices uncertain. Our current understanding of the processes that trigger type I ELMs and the size of the resultant energy loss are reviewed and compared to experimental data and ideas for further development are discussed.

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“…This will allow for a more thorough comparison of the ELM simulations based on the presented model and ELMs observed in DIII-D. The model was recently tested on JET discharge 79459, which fits into the large distance regime, with very good agreement between observed ELM heat flux and field line penetration depth structures on both targets [24].…”

Section: Discussionmentioning

confidence: 83%

Dependence of a current driven ELM self-amplification process on the plasma shape

2012

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The numerical model of the non-linear evolution of edge-localized modes (ELMs) in tokamaks being used in this paper assumes that thermoelectric currents flow in short connection length flux tubes, initially established by error fields or other non-axisymmetric magnetic perturbations. The additional magnetic perturbation of the current filaments changes the magnetic topology. In a self-amplification process, more flux tubes are created which eventually allow more thermoelectric current to flow through the plasma edge. The process of flux tube formation is highly sensitive to the position of the secondary X-point in typical single null discharges in DIII-D. A new scenario for cases with large distances Δs between the secondary X-point and the primary separatrix is presented. In the numerical simulations, as Δs is increased the current evolution through short connection length flux tubes changes significantly. Ultimately, a final state with large stripe structures is found that results in footprints on the vessel wall which are similar to those found when Δs is small (Wingen et al 2010 Phys. Rev. Lett. 104 175001).

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Thermoelectric currents and their role during ELM formation in JET

Cited by 10 publications

References 31 publications

Findings of pre-ELM structures through the observation of divertor heat load patterns at JET with appliedn= 2 perturbation fields

Findings of pre-ELM structures through the observation of divertor heat load patterns at JET with appliedn= 2 perturbation fields

Recent progress in understanding the processes underlying the triggering of and energy loss associated with type I ELMs

Dependence of a current driven ELM self-amplification process on the plasma shape

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