Predicting operational windows of ELMs suppression by resonant magnetic perturbations in the DIII-D and KSTAR tokamaks

Hu, Qiming; Nazikian, R.; Logan, N. C.; Park, J.-K.; Paz-Soldan, C.; Yang, SeongMoo; Grierson, B. A.; In, Y.; Jeon, Y.M.; Kim, M.; Kim, SangKyeun; Orlov, D. M.; Park, G. Y.; Yu, Q.

doi:10.1063/5.0043018

Cited by 25 publications

(37 citation statements)

References 80 publications

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“…The phenomenon of density 'pump-out' typically seen with RMP application is also far from being fully understood. The possible candidates as E × B convective transport [26], NTV particle drift [22], polarization current [29] and increased turbulence with RMPs [30] were proposed by theory and modelling, but for the moment there is no global approach combining all these mechanisms which possibly all play a role in density 'pump-out'.…”

Section: Introductionmentioning

confidence: 99%

Non-linear MHD modelling of edge localized modes suppression by resonant magnetic perturbations in ITER

Bécoulet¹,

Huijsmans²,

Passeron³

et al. 2022

Nucl. Fusion

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Edge Localized Modes (ELMs) suppression by Resonant Magnetic Perturbations (RMPs) was studied with the non-linear MHD code JOREK for the ITER H-mode scenarios at 15MA,12.5MA,10MA/5.3T. The main aim of this work was to demonstrate that ELMs can be suppressed by RMPs while the divertor 3D footprints of heat and particle fluxes remain within divertor material limits. The unstable peeling-ballooning modes responsible for ELMs without RMPs were modelled first for each scenario using numerically accessible parameters for ITER. Then the stabilization of ELMs by RMPs was modelled with the same parameters. RMP spectra, optimized by the linear MHD MARS-F code, with main toroidal harmonics N=2, N=3, N=4 have been used as boundary conditions of the computational domain of JOREK, including realistic RMP coils, main plasma, Scrape Off Layer (SOL) divertor and realistic first wall. The model includes all relevant plasma flows: toroidal rotation, two fluid diamagnetic effects and neoclassical poloidal friction. With RMPs, the main toroidal harmonic and the non-linearly coupled harmonics remain dominant at the plasma edge, producing saturated modes and a continuous MHD turbulent transport thereby avoiding ELM crashes in all scenarios considered here. The threshold for ELM suppression was found at a maximum RMP coils current of 45kAt-60kAt compared to the coils maximum capability of 90kAt. In the high beta poloidal steady-state 10MA/5.3T scenario, a rotating QH-mode without ELMs was observed even without RMPs. In this scenario with RMPs N=3, N=4 at 20kAt maximum current in RMP coils, similar QH-mode behavior was observed however with dominant edge harmonic corresponding to the main toroidal number of RMPs. The 3D footprints with RMPs show the characteristic splitting with the main RMP toroidal symmetry. The maximum radial extension of the footprints typically was ~20 cm in inner divertor and ~40 cm in outer divertor with stationary heat fluxes decreasing further out from the initial strike point from ~5MW/m2 to ~1MW/m2 assuming a total power in the divertor and walls is 50MW.

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Section: Introductionmentioning

confidence: 99%

Non-linear MHD modelling of edge localized modes suppression by resonant magnetic perturbations in ITER

Bécoulet¹,

Huijsmans²,

Passeron³

et al. 2022

Nucl. Fusion

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“…To compare with the conventional feed-forward cases reported by KSTAR [17,29], the RMP configuration was set to n = 1 with 90 • phasing. In addition, q 95 is set around 4.8 right after the H-mode transition time at t = 3.14 s. When the first ELM crash occurs, q 95 ≈ 4.9. q 95 for the reference discharge at the H-mode transition moment is near the lower bound for the n = 1 ELM crash suppression [29,30].…”

Section: Setup For the Reference H-mode Dischargementioning

confidence: 78%

Preemptive RMP-driven ELM crash suppression automated by a real-time machine-learning classifier in KSTAR

Shin¹,

Hahn²,

Kim³

et al. 2022

Nucl. Fusion

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Suppression or mitigation of edge-localized mode (ELM) crashes is necessary for ITER. The strategy to suppress all the ELM crashes by the resonant magnetic perturbation (RMP) should be applied as soon as the first low-to-high confinement (L-H) transition occurs. A control algorithm based on real-time machine learning (ML) enables such an approach: it classifies the H-mode transition and the ELMy phase in real-time and automatically applies the preemptive RMP. This paper reports the algorithm design, which is now implemented in the KSTAR plasma-control system, and the corresponding experimental demonstration of typical high-δ KSTAR H-mode plasmas. As a result, all initial ELM crashes are suppressed with an acceptable safety factor at the edge (q95) and with RMP field adjustment. Moreover, the ML-driven ELM-crash-suppression discharges remain stable without further degradation due to the regularization of the plasma pedestal.

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“…应与等离子体边缘剥离模的稳定性有关，对 ASDEX Upgrade [30] 和 ITER [40] 的模拟研究也证明了这一点。研究表明这个特定区域通常为等离子体边缘台基区，显然，新有理面经过等离子体边缘台基区时，有理面处的大磁岛更容易加速该区域粒子的径向输运，从而有利于实现 ELMs 的控制 [47]…”

Section: 数值模拟结果unclassified

Modelling study of fluid and kinetic responses of plasmas to resonant magnetic perturbation

Zhou¹,

Hu²,

Liu³

et al. 2023

Acta Phys. Sin.

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It is well known that large-scale type-I edge localized modes (ELMs) may pose serious risks to machine components in future large fusion devices. The resonant magnetic perturbation (RMP), generated by magnetic coils external to the plasma, can either suppress or mitigate ELMs, as has been shown in recent experiments on several present-day fusion devices. Understanding ELM control with RMP may involve various physics. This work focuses on understanding of the roles of three key physical quantities:the edge safety factor, the RMP coil current and the particle drift kinetic effects from thermal and fusion-born α-particles. Full toroidal computations are performed using the MARS-F/K codes. It shows that both of the plasma response based figures of merit-one is the pitch resonant radial field component near the plasma edge and the other is the plasma displacement near the X-point of the separatrix-consistently yield the same periodic amplification as q95 varies. The number of peaks y is positively correlated with the toroidal number n, i.e., y≈n△q95 with △q95=3.5. The peak window in q95 occurs when a new resonant surface passes through a specific region of the plasma edge. Two-dimensional parameter scans, for the edge safety factor and the coil phasing between the upper and lower rows of coils, yield a linear dependence between the optimal/worst current phase difference and q95, which can be well fitted by a simple analytic model. The optimal value of coil current amplitude is sensitive to n. Compared with the same current amplitude assumed for the two/three rows of coils, the optimal current amplitude can increase the ξX but does not alter the prediction of the relative toroidal phase difference. More advanced response model, including kinetic resonances between the RMP perturbation and drift motions of thermal particles and fusion-born alphas, shows that the modification of kinetic effects should be considered in order to better describe the plasma response to RMP fields in high-β plasmas. The fluid response model with a strong parallel sound wave damping (κ||=1.5) can well predict the plasma response for the DEMO-like equilibria. For low β plasma, the kinetic response is consistent with the fluid response, independent of the presence or absence of a strong parallel sound wave damping.

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Predicting operational windows of ELMs suppression by resonant magnetic perturbations in the DIII-D and KSTAR tokamaks

Cited by 25 publications

References 80 publications

Non-linear MHD modelling of edge localized modes suppression by resonant magnetic perturbations in ITER

Non-linear MHD modelling of edge localized modes suppression by resonant magnetic perturbations in ITER

Preemptive RMP-driven ELM crash suppression automated by a real-time machine-learning classifier in KSTAR

Modelling study of fluid and kinetic responses of plasmas to resonant magnetic perturbation

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