Nonlinear coupling induced toroidal structure of edge localized modes

Mink, A. F.; Hoelzl, M.; Wolfrum, E.; Orain, F.; Dunne, M.; Lessig, A.; Pamela, S.; Mänz, P.; Maraschek, M.; Huijsmans, G. T. A.; Bécoulet, M.; Laggner, F. M.; Cavedon, M.; Lackner, K.; Günter, S.; Stroth, U.

doi:10.1088/1741-4326/aa98f7

Cited by 35 publications

(50 citation statements)

References 55 publications

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“…Typically, while the maximum pressure gradient remains clamped, the pedestal grows further inwards until a large ELM crash appears. Often, precursor modes are observed before, which have a similar spatial structure as the ELM crash . JOREK simulations so far did not concentrate strongly on the inter‐ELM phase.…”

Section: Type‐i Elmsmentioning

confidence: 99%

“…Refined evaluation methods for the magnetic measurements at ASDEX Upgrade allows the extraction of the toroidal spectrum during an ELM cycle, revealing dominant n = 2…5 components for the present discharge, corresponding to a clear shift from the linear stability analysis in which n = 5, 6 are dominating . In the simulation, n = 4 is dominating during the ELM crash ( t − t ELM = 0…2 ms), n = 1…6 have significant amplitudes, and n ≥ 7 are lower by at least a factor two in average energies.…”

Section: Type‐i Elmsmentioning

confidence: 99%

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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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Section: Type‐i Elmsmentioning

confidence: 99%

Section: Type‐i Elmsmentioning

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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“…Note that linear simulations show that n ≥ 9 modes are also linearly unstable, with a growth rate smaller than n = 7 and 8. Since these two most unstable modes dominate the linear growth and the low n ≤ 6 modes are non-linearly dominant [25], it was chosen to discard the n ≥ 9 modes to reduce the computation time of the simulations. This "natural" ELM without RMPs is compared to the cases with RMPs.…”

Section: Rmp Effect On Elmsmentioning

confidence: 99%

“…In Fig. 8, negative n mode numbers correspond to modes rotating in the electron diamagnetic direction and indicates the movement of edge modes, while positive mode numbers describe core modes rotating in the ion diamagnetic direction [25]. The comparison of the ELM mitigation ( Fig.…”

Section: B Mechanism Of the Mode Braking During Elm Suppressionmentioning

confidence: 99%

Non-linear modeling of the threshold between ELM mitigation and ELM suppression by resonant magnetic perturbations in ASDEX upgrade

et al. 2019

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The interaction between Edge Localized Modes (ELMs) and Resonant Magnetic Perturbations (RMPs) is modeled with the magnetohydrodynamic code JOREK using experimental parameters from ASDEX Upgrade discharges. According to the modeling, the ELM mitigation or suppression is optimal when the amplification of both tearing and peeling-kink responses result in a better RMP penetration. The ELM mitigation or suppression is not only due to the reduction of the pressure gradient, but predominantly arises from the toroidal coupling between the ELMs and the RMPinduced mode at the plasma edge, forcing the edge modes to saturate at a low level. The bifurcation from ELM mitigation to ELM suppression is observed when the RMP amplitude is increased. ELM mitigation is characterized by rotating modes at the edge, while the mode locking to RMPs is induced by the resonant braking of the electron perpendicular flow in the ELM suppression regime.

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“…In this regard, our model may be considered complementary to the existing trigger theory 25,26 and the nonlinear multi-harmonic simulations where the energy of the linearly dominant mode is redistributed into a broad spectrum as approaching to the ELM crash. 22,27,28 To conclude, it is critical to consider the time-varying A for explanation of dynamic features in ELM phenomena using the given models (1) and (12)- (13) for single and coupled-modes, respectively.…”

Section: Discussionmentioning

confidence: 99%

Effect of time-varying flow-shear on the nonlinear stability of the boundary of magnetized toroidal plasmas

Hwang

Leconte

et al. 2018

AIP Advances

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We propose a phenomenological yet very general model in a form of generalized complex Ginzburg-Landau equation to understand the dynamics of the quasi-periodic fluid instabilities (called edge-localized modes) in the boundary of toroidal magnetized high-temperature plasmas. The model reproduces key dynamical features of the boundary instabilities observed in the high-confinement state plasmas on the KSTAR tokamak, including quasi-steady states characterized by field-aligned filamentary eigenmodes, transitions between different eigenmodes, and rapid transition to non-modal filamentary structure prior to the relaxation. It is found that the inclusion of time-varying perpendicular sheared flow is crucial for reproducing the observed dynamical features.

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Nonlinear coupling induced toroidal structure of edge localized modes

Cited by 35 publications

References 55 publications

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

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

Non-linear modeling of the threshold between ELM mitigation and ELM suppression by resonant magnetic perturbations in ASDEX upgrade

Effect of time-varying flow-shear on the nonlinear stability of the boundary of magnetized toroidal plasmas

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