Unveiling the structure and dynamics of peeling mode in quiescent high-confinement tokamak plasmas

Kamiya, K.; Itoh, K.; Aiba, N.; Oyama, N.; Honda, M.; Isayama, A.

doi:10.1038/s42005-021-00644-x

Cited by 6 publications

(2 citation statements)

References 34 publications

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“…Similar oscillations to the ones simulated here are also reported in the literature of QH-mode experiments in JT60-U [50]. During the QH-mode phase, the plasma is observed to be in a dynamical steady-state where the dominant peeling mode undergoes repeated growth and damping cycles.…”

Section: Limit Cycle Oscillationssupporting

confidence: 89%

MHD simulations of formation, sustainment and loss of quiescent H-mode in the all-tungsten ASDEX Upgrade

et al. 2023

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Periodic edge localized modes (ELMs) are the non-linear consequences of pressure-gradient-driven ballooning modes and current-driven peeling modes becoming unstable in the pedestal region of high confinement fusion plasmas. In future tokamaks like ITER, large ELMs are foreseen to severely affect the lifetime of wall components as they transiently deposit large amounts of heat onto a narrow region at the divertor targets. Several strategies exist for avoidance, suppression, or mitigation of these instabilities, such as the naturally ELM-free quiescent H-mode (QH-mode). In the present article, an ASDEX Upgrade equilibrium that features a QH-mode is investigated through non-linear extended MHD simulations covering the dynamics over tens of milliseconds. The equilibrium is close to the ideal peeling limit and non-linearly develops saturated modes at the edge of the plasma. A dominant toroidal mode number of $n=1$ is found, for which the characteristic features of the edge harmonic oscillation are recovered.The saturated modes contribute to heat and particle transport preventing pedestal build-up to the ELM triggering threshold. The non-linear dynamics of the mode, in particular its interaction with the evolution of the edge safety factor is studied, which suggest a possible new saturation mechanism for the QH-mode.The simulations show good qualitative and quantitative agreement to experiments in AUG. In particular, the processes leading to the termination of QH-mode above a density threshold is studied, which results in the transition into an ELM regime. In the vicinity of this threshold, limit cycle oscillations are observed.

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Section: Limit Cycle Oscillationssupporting

confidence: 89%

MHD simulations of formation, sustainment and loss of quiescent H-mode in the all-tungsten ASDEX Upgrade

et al. 2023

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“…In this section, we investigate the impact of coupled rotation and the ω * i effects on the stability of MHD modes at the edge pedestal in a QH-mode plasma in JT-60U. The discharge number/time/n EHO are E42868/6.5 s/1 or 2, and the time traces of the Fourier analysis of the signals and several plasma parameters of this discharge are shown in figure 5; the details are explained in [29]. In the plasma, B t and I p are clockwise from the top view of the torus, and the toroidal rotation of the impurity (carbon) is in the counter-I p direction as in the DIII-D cases.…”

Section: Results Of the Stability Analysis In A Jt-60u Plasmamentioning

confidence: 99%

Stabilization of kink/peeling modes by coupled rotation and ion diamagnetic drift effects in quiescent H-mode plasmas in DIII-D and JT-60U

Aiba¹,

Chen²,

Kamiya³

et al. 2021

Nucl. Fusion

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Magnetohydrodynamic stability at the edge pedestal in several quiescent H-mode (QH-mode) plasmas in DIII-D and JT-60U experiments was analyzed by considering plasma rotation and ion diamagnetic drift effects. It was identified that a kink/peeling mode, which is a prime candidate for a trigger of edge harmonic oscillation in QH-mode, is stabilized by plasma rotation when considering the ion diamagnetic drift simultaneously in both experiments. The stabilizing effect by rotation becomes more effective in case using the rotation profile of the main ion species evaluated by assuming radial force balance. In addition, when inverting the rotation direction, it was found that the kink/peeling mode is more stabilized when considering the rotation of the main ion species, though the mode is less stabilized by the rotation of impurity ion species. The result implies that the kink/peeling mode stability in QH-mode plasmas is sensitive to how the rotation profile is evaluated, but it is shown that a qualitative trend stabilizing the kink/peeling mode by rotation can be reproduced with the poloidal rotation profile of an impurity predicted numerically based on the neoclassical theory.

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Prospects of core–edge integrated no-ELM and small-ELM scenarios for future fusion devices

Viezzer

Austin

Bernert

et al. 2023

Nuclear Materials and Energy

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Unveiling the structure and dynamics of peeling mode in quiescent high-confinement tokamak plasmas

Cited by 6 publications

References 34 publications

MHD simulations of formation, sustainment and loss of quiescent H-mode in the all-tungsten ASDEX Upgrade

MHD simulations of formation, sustainment and loss of quiescent H-mode in the all-tungsten ASDEX Upgrade

Stabilization of kink/peeling modes by coupled rotation and ion diamagnetic drift effects in quiescent H-mode plasmas in DIII-D and JT-60U

Prospects of core–edge integrated no-ELM and small-ELM scenarios for future fusion devices

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