Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

Suttrop, W.; Kirk, A.; Nazikian, R.; Leuthold, N.; Strumberger, E.; Willensdorfer, M.; Cavedon, M.; Dunne, M.; Fischer, R.; Fietz, S.; Fuchs, Julien; Liu, Y Q; McDermott, R. M.; Orain, F.; Ryan, D. A.; Viezzer, E.

doi:10.1088/0741-3335/59/1/014049

Cited by 70 publications

(108 citation statements)

References 93 publications

(144 reference statements)

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“…Such a correlation has previously been obtained in the modelling of several tokamak devices 4,7,8,13,25 and will be further confirmed by the new results presented in this work. The role of the edge-peeling response in ELM suppression is less exploited in the previous work and is therefore one of the focusing points in this study.…”

Section: Introductionsupporting

confidence: 88%

“…In particular, the fluid model predicted optimal coil phasing, which maximizes the edge-peeling response, agrees well with the best achievable ELM mitigation in experiments. 33 This is confirmed by MARS-F, [10][11][12] NEMEC, 4 and JOREK 13 computations. In particular, systematic scans with varying edge safety factor 12,37 as well as plasma pressure 37 yield simple analytic fitting formulas for the optimal coil phasing, with varying plasma conditions.…”

Section: Modelling Elm Mitigation Experimentssupporting

confidence: 57%

“…Full ELM suppression has recently been achieved in ASDEX Upgrade under low pedestal collisionality conditions (with effective electron collisionality at the pedestal top Ã ped Շ0:4). 4 This was possible, however, only with the increased plasma shaping. More specifically, it was found that increasing the upper triangularity helps to obtain the ELM suppression.…”

Section: -8 Liu Et Almentioning

confidence: 99%

“…In fact, full suppression of type-I ELM, under ITER relevant (low) collisionality conditions, has been reported on several present-day devices, including DIII-D, 1 KSTAR, 2 EAST, 3 and ASDEX Upgrade. 4 Even in devices where ELM suppression has so far not been achieved, the ELM bursting frequency is significantly increased with reduced amplitude per burst. This is referred to as ELM mitigation, which is still of significant benefit in terms of reducing the peak heat flux load on the plasma facing components.…”

Section: Introductionmentioning

confidence: 99%

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Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP fields

Liu

Kirk

et al. 2017

Physics of Plasmas

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Extensive modelling efforts of the plasma response to the resonant magnetic perturbation fields, utilized for controlling the edge localized mode (ELM), help to identify the edge-peeling response as a key factor, which correlates to the observed ELM mitigation in several tokamak devices, including MAST, ASDEX Upgrade, EAST, and HL-2A. The recently observed edge safety factor window for ELM mitigation in HL-2A experiments is explained in terms of the edge-peeling response. The computed plasma response, based on toroidal single fluid resistive plasma model with different assumption of toroidal flows, is found generally larger in ELM suppressed cases as compared to that of the ELM mitigated cases, in ASDEX Upgrade and DIII-D. The plasma shaping, in particular, the plasma triangularity, contributes to the enhanced plasma response. But the shaping does not appear to be the sole factor-other factors such as the (higher) pedestal pressure and/or current can also lead to increased edge-peeling response.

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Section: Introductionsupporting

confidence: 88%

Section: Modelling Elm Mitigation Experimentssupporting

confidence: 57%

Section: -8 Liu Et Almentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP fields

Liu

Kirk

et al. 2017

Physics of Plasmas

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“…Further evidence of the correlation between the observed high-energy feature and the ELMs was found in an ELMsuppressed regime, achieved via the application of external magnetic perturbations (MPs) at AUG [26,27]. Figure 3(b) shows the evolution of the FILD gyroradius profile together with the divertor current time trace (in white) in such a case.…”

mentioning

confidence: 79%

Beam-Ion Acceleration during Edge Localized Modes in the ASDEX Upgrade Tokamak

et al. 2018

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The acceleration of beam ions during edge localized modes (ELMs) in a tokamak is observed for the first time through direct measurements of fast-ion losses in low collisionality plasmas. The accelerated beamion population exhibits well-localized velocity-space structures which are revealed by means of tomographic inversion of the measurement, showing energy gains of the order of tens of keV. This suggests that the ion acceleration results from a resonant interaction between the beam ions and parallel electric fields arising during the ELM. Orbit simulations are carried out to identify the mode-particle resonances responsible for the energy gain in the particle phase space. The observation motivates the incorporation of a kinetic description of fast particles in ELM models and may contribute to a better understanding of the mechanisms responsible for particle acceleration, ubiquitous in astrophysical and space plasmas.

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Insights into type‐I edge localized modes and edge localized mode control from JOREK non‐linear magneto‐hydrodynamic simulations

Hoelzl

Huijsmans

Orain

et al. 2018

Contributions to Plasma Physics

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Edge localized modes (ELMs) are repetitive instabilities driven by the large pressure gradients and current densities in the edge of H‐mode plasmas. Type‐I ELMs lead to a fast collapse of the H‐mode pedestal within several hundred microseconds to a few milliseconds. Localized transient heat fluxes to divertor targets are expected to exceed tolerable limits for ITER, requiring advanced insights into ELM physics and applicable mitigation methods. This paper describes how non‐linear magneto‐hydrodynamic (MHD) simulations can contribute to this effort. The JOREK code is introduced, which allows the study of large‐scale plasma instabilities in tokamak X‐point plasmas covering the main plasma, the scrape‐off layer, and the divertor region with its finite element grid. We review key physics relevant for type‐I ELMs and show to what extent JOREK simulations agree with experiments and help reveal the underlying mechanisms. Simulations and experimental findings are compared in many respects for type‐I ELMs in ASDEX Upgrade. The role of plasma flows and non‐linear mode coupling for the spatial and temporal structure of ELMs is emphasized, and the loss mechanisms are discussed. An overview of recent ELM‐related research using JOREK is given, including ELM crashes, ELM‐free regimes, ELM pacing by pellets and magnetic kicks, and mitigation or suppression by resonant magnetic perturbation coils (RMPs). Simulations of ELMs and ELM control methods agree in many respects with experimental observations from various tokamak experiments. On this basis, predictive simulations become more and more feasible. A brief outlook is given, showing the main priorities for further research in the field of ELM physics and further developments necessary.

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Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

Cited by 70 publications

References 93 publications

Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP fields

Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP fields

Beam-Ion Acceleration during Edge Localized Modes in the ASDEX Upgrade Tokamak

Insights into type‐I edge localized modes and edge localized mode control from JOREK non‐linear magneto‐hydrodynamic simulations

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