Modelling of edge localised modes and edge localised mode control

Huijsmans, Gta Guido; Chang, C. S.; Ferraro, N.M.; Sugiyama, L.; Waelbroeck, F. L.; Xu, X. Q.; Loarte, A.; Futatani, S.

doi:10.1063/1.4905231

Cited by 44 publications

(50 citation statements)

References 120 publications

(194 reference statements)

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“…The increase in plasma stored energy is limited by the onset of periodic bursts called Edge Localised Modes (ELMs) [3][4][5][6][7][8][9], each of which leading to a transient collapse of the pedestal. Understanding these modes is imperative for correctly predicting fusion performance and controlling ELMs in ITER [10,11]. The most widely accepted model to explain the occurrence of ELMs is the peeling ballooning (PB) model [12][13][14] .…”

Section: Introductionmentioning

confidence: 99%

Long-lived coupled peeling ballooning modes preceding ELMs on JET

et al. 2019

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In some JET discharges, type-I Edge Localised Modes (ELMs) are preceded by a class of low frequency oscillations [Perez et al Nucl. Fusion 44 (2004) 609]. While in many cases the ELM is triggered during the growth phase of this oscillation, it is also observed that this type of oscillations can saturate and last for several tens of ms until an ELM occurs. In order to identify the nature of these modes, a wide pre-ELM oscillation database including detailed pedestal profile information has been assembled and analysed in terms of MHD stability parameters. The existence domain of these pre-ELM oscillations and the statistical distribution of toroidal mode numbers (n) up to n = 16 has been mapped in ballooning alpha (α ball) and either edge current density (J edge) or pedestal collisionality (ν * ee,ped) coordinates and compared to linear MHD stability predictions. The pre-ELM oscillations are reliably observed when the J/α ratio is high enough for the pedestal to access the coupled peelingballooning (PB) domain (aka stability nose). Reversely, when the pedestal is found to be in or near the high-n ballooning domain (which is at low J/α ratio), ELMs are usually triggered promptly, i.e. with no detectable pre-ELM oscillations, or with pre-ELM oscillations only observable on ECE whose n appears to be too high to be resolved by the magnetics. Individual discharges can sometimes exhibit a fairly wide range of pre-ELM mode numbers, but for a wider database the statistical n-number domains are found to be well ordered along the J-α stability boundary and behave as expected from PB theory: the higher the J/α ratio, the lower the mode's measured n tends to be. Within the measurement uncertainties, the measured n is usually found to be compatible with the most unstable n predicted by the linear stability code MISHKA1. These results confirm the earlier hypothesis that these modes are coupled peelingballooning modes, and extend and generalise to higher mode numbers the work by Huysmans

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Section: Introductionmentioning

confidence: 99%

Long-lived coupled peeling ballooning modes preceding ELMs on JET

et al. 2019

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“…A comprehensive review of non‐linear simulations of ELMs and their control by various codes can be found in ref. [].…”

Section: Introductionmentioning

confidence: 99%

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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“…Furthermore, non-linear MHD modelling, using JOREK [27], M3D-C1 [28,29], BOUT++ [30], NIMROD [31], as has been well summarised in Ref. [32] , has provide crucial understanding of the ELM and ELM control physics.…”

Section: Introductionmentioning

confidence: 99%

Modelling of plasma response to 3D external magnetic field perturbations in EAST

Yang

Sun

Liu

et al. 2016

Plasma Phys. Control. Fusion

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Sustained mitigation and/or suppression of the type-I edge localized modes (ELMs) have been achieved in EAST H-mode plasmas, utilizing the resonant magnetic perturbation (RMP) fields, produced by two rows of magnetic coils located just inside the vacuum vessel. Systematic toroidal modelling of the plasma response to these RMP fields, with various coil configurations (with dominant toroidal mode number n=1, 2, 3, 4) in EAST, is for the first time carried out by using the MARS-F code [Liu Y et al 2000 Phys. Plasmas 7 3681], with results reported here. In particular, the plasma response is computed with varying coil phasing (the toroidal phase difference of the coil currents) between the upper and lower rows of coils, from 0 to 360 degrees. Four figures of merit, constructed based on the MARS-F computations, are used to determine the optimal coil phasing. The modelled results, taking into account the 2 plasma response, agree well with the experimental observations in terms of the coil phasing, for both the mitigated and the suppressed ELM cases in EAST experiments.This study provides a crucial confirmation of the role of the plasma edge peeling response in the ELM control, complementing similar studies carried out for other tokamak devices.

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Modelling of edge localised modes and edge localised mode control

Cited by 44 publications

References 120 publications

Long-lived coupled peeling ballooning modes preceding ELMs on JET

Long-lived coupled peeling ballooning modes preceding ELMs on JET

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

Modelling of plasma response to 3D external magnetic field perturbations in EAST

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