Measurement of 3D plasma response to external magnetic perturbations in the presence of a rotating external kink

Shiraki, D.; Angelini, Sarah; Byrne, P.J.; DeBono, B.; Hughes, Paul E.; Levesque, J.P.; Mauel, M. E.; Maurer, D.A.; Navratil, G.A.; Peng, Qian; Rath, N.; Rhodes, Dov; Stoafer, C.C.

doi:10.1063/1.4824345

Cited by 16 publications

(22 citation statements)

References 23 publications

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“…Notice that, the n=2 mode is linearly stable in our case, and we can say that RMP nonlinearly drives the n=2 KPM. This result is consistent with the previous studies where peeling-like mode was observed in the response under RMP [40][41][42]. Interestingly, perturbed radial E B flow is generated at the edge region due to KPM.…”

Section: Iv-1 Kink-tearing Plasma Response Under Rmpsupporting

confidence: 93%

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

et al. 2020

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The impact of n=2 resonant magnetic perturbation (RMP) on the pedestal and peeling-ballooning mode (PBM) is investigated using the nonlinear 3D MHD code JOREK. It is based on the reduced MHD equations (viscos-resistive MHD), and the experimental parameters from the RMP-driven Edge localized mode (ELM) suppression discharge in KSTAR. In this study, n=2 kink-peeling mode was triggered through nonlinear coupling with RMP, and the pedestal is degraded by increased radial transport due to both tearing and kink-peeling response. The ELM mitigation and suppression are observed when RMP of sufficient amplitude is applied. ELM suppression was characterized by spatial locking of mode structure. In the simulation, the ELM suppression is not only due to the degraded pedestal but is also related to the mode coupling between the PBMs and the RMP-induced mode at the plasma edge. The role of PBM locking in mode suppression is suggested in terms of mode coupling.

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Section: Iv-1 Kink-tearing Plasma Response Under Rmpsupporting

confidence: 93%

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

et al. 2020

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“…This is illustrated in figures 9((a) and (c)). In addition to the plasma response from the RMP, the poloidal magnetic field sensors also show rotating m/n = 3/1 kink instabilities, as described previously in [28,29]. The influence of the external kink mode is most apparent near ∼ t 3 ms when the kink oscillations approach ∆ ≈ B 5 p G. At the same time, these kink oscillations correspond to changes in the plasma's horizontal displacement and SOL currents.…”

Section: Resonant Magnetic Perturbationssupporting

confidence: 57%

“…SOL currents of comparable amplitude to the above kink mode currents are also measured in response to applied resonant magnetic perturbations (RMPs). Programmed applications of RMPs are used to measure the dispersion characteristics of resistive wall modes [27], explore the 3D plasma response in the presence of rotating kink modes [28], and investigate RMP-induced disruption limits and enhanced plasma-wall interactions [29]. The use of 'phase-flip' RMPs, where the phase of the applied field is quickly rotated by 180 during its application, is especially useful for the detection of relatively small changes in the plasma due to small non-axisymmetric magnetic fields.…”

Section: Resonant Magnetic Perturbationsmentioning

confidence: 99%

Measurement of scrape-off-layer current dynamics during MHD activity and disruptions in HBT-EP

et al. 2017

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We report scrape-off layer (SOL) current measurements during magnetohydrodynamic (MHD) mode activity, resonant magnetic perturbations (RMPs), and disruptions in the High Beta Tokamak-Extended Pulse (HBT-EP) device. Currents are measured via segmented plasma current Rogowski coils, jumpers running toroidally between otherwise-isolated vessel sections, and a grounded electrode in the scrape-off layer. These currents strongly depend on the plasma's major radius, and amplitude and phase of non-axisymmetric field components. SOL currents connecting through the vessel are seen to reach ∼0.2-0.5% of the plasma current during typical kink activity and RMPs. Plasma current asymmetries and scrape-off-layer currents generated during disruptions, which are commonly called halo currents, reach ∼4% of I p . Asymmetric toroidal currents between vessel sections rotate at tens of kHz through most of the current quench, then symmetrize once I p reaches ∼30% of its pre-disruptive value. Toroidal jumper currents oscillate between co-and counter-I p , with co-I p being dominant on average during disruptions. A relative increase in local plasma current measured by a segmented I p Rogowski coil correlates with counter-I p current in the nearest toroidal jumper. Measurements are interpreted in the context of two models that produce contrary predictions for the toroidal vessel current polarity during disruptions. Plasma current asymmetry measurements are consistent with both models, and SOL currents scale with plasma displacement toward the vessel wall. The design of an upcoming SOL current diagnostic and control upgrade is also briefly presented.

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“…Theoretical studies of island dynamics have been carried out by Fitzpatrick in several papers [41][42][43]. The observed evolution of the island during RMP is very similar to that in reversed field pinches, as described in EXTRAP T2R [44,45] and HBT-EP [46,47].…”

Section: Island Locking To the Rotating Rmpmentioning

confidence: 80%

Overview of the recent research on the J-TEXT tokamak

Zhuang

Gentle

Diamond³

et al. 2015

Nucl. Fusion

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The experimental research over last two years on the J-TEXT tokamak is summarized and presented in the paper. The high-performance polarimeter-interferometer developed on J-TEXT, aiming to measure electron density and Faraday angle simultaneously, has time response up to 1 µs, phase resolution < 0.1 • and spatial resolution ∼3 cm. Such high resolution permits investigations of fast equilibrium dynamics as well as magnetic and density perturbations associated with magnetohydrodynamic instabilities. Particle transport due to the sawtooth crashes is analysed. The sawteeth only partially flatten the core density profile and recovery between crashes implies an inward pinch velocity extending to the centre. The resonant magnetic perturbation (RMP) system on J-TEXT can generate a rotating helical field perturbation with a maximum rotation frequency up to 6 kHz, and dominant resonant modes of m/n = 2/1, 3/1 or 1/1. It is found that tearing modes can be easily locked and then rotate together with a rotating RMP. The effects of RMPs on plasma flows and fluctuations are studied with Langmuir probe arrays at the plasma edge. The toroidal velocity increases and the radial electric field decreases with RMP coil current when the RMP current is no more than 5 kA. When the RMP current reaches 6 kA, the toroidal velocity profile becomes flattened near the last closed flux surface. The geodesic acoustic mode is damped in most of the edge region, while the low frequency zonal flow is damped inside the islands, but increases at its boundary.

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Measurement of 3D plasma response to external magnetic perturbations in the presence of a rotating external kink

Cited by 16 publications

References 23 publications

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

Nonlinear modeling of the effect of n = 2 resonant magnetic field perturbation on peeling-ballooning modes in KSTAR

Measurement of scrape-off-layer current dynamics during MHD activity and disruptions in HBT-EP

Overview of the recent research on the J-TEXT tokamak

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