Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP fields

Liu, Yueqiang; Kirk, A.; Li, Li; In, Y.; Nazikian, R.; Sun, Yuan; Suttrop, W.; Lyons, Brendan; Ryan, D. A.; Wang, Shuo; Yang, Xu; Zhou, Lina

doi:10.1063/1.4978884

Cited by 52 publications

(74 citation statements)

References 42 publications

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“…(a) The experimental ratio of the ELM frequency with RMP (shading region) to that without RMP; (b) the simulated ratio of the plasma surface displacement near the X-point to that near the outboard mid-plane. Reproduced with the permission from[20] …”

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confidence: 99%

Overview of HL-2A recent experiments

Xu¹,

Duan²,

Liu³

et al. 2019

Nucl. Fusion

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ITER and to the advanced tokamak operation (e.g. the operation of future HL-2M), such as the access of H-mode, energetic particle physics, edge-localized mode (ELM) mitigation/suppression and disruption mitigation. Since the 2016 Fusion Energy Conference, the HL-2A team has focused on the investigations on the following areas: (i) pedestal dynamics and L-H transition, (ii) techniques of ELM control, (iii) the turbulence and transport, (iv) energetic particle physics. The HL-2A results demonstrated that the increase of mean E × B shear flow plays a key role in triggering L-I and I-H transitions. While the change of E × B flow is mainly induced by the ion pressure gradient. Both mitigation and suppression of ELMs were realized by laser blow-off (LBO) seeded impurity (Al, F e, W). The 30% N e mixture supersonic molecular beam injection (SMBI) seeding also robustly induced ELM mitigation. The ELMs were mitigated by low-hybrid current drive (LHCD). The stabilization of m/n=1/1 ion fishbone activities by electron cyclotron resonance heating (ECRH) was found on the HL-2A. A new m/n=2/1 ion fishbone activity was observed recently, and the modelling indicated that passing fast ions dominantly contribute to the driving of 2/1 fishbone. The non-linear coupling between toroidal Alfven eigenmode (TAE) and tearing mode (TM) leads to the generation of a high frequency mode with the toroidal mode number n=0. The turbulence is modulated by tearing mode when the island width exceeds a threshold and the modulation is localized merely in the inner area of the islands. Meanwhile, turbulence radially spreading takes place across the island region.

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confidence: 99%

Overview of HL-2A recent experiments

Xu¹,

Duan²,

Liu³

et al. 2019

Nucl. Fusion

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“…This rotation variation can be compared with the cross-field electron flow required for shielding the resistive response in linear MHD model predictions. For ELM suppression plasmas in AUG and DIII-D several such calculations have been made [38,39,40]. Single-fluid MARS-F calculations for the AUG experimental case [39] show that a fairly small cross-field flow, of the order of |ω| ≤ 6 krad/s, is required to obtain a significant resistive response at a resonant surface.…”

Section: Summary and Discussionmentioning

confidence: 99%

Experimental conditions to suppress edge localised modes by magnetic perturbations in the ASDEX Upgrade tokamak

Suttrop,

Kirk,

Bobkov

et al. 2018

Preprint

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Access conditions for full suppression of Edge Localised Modes (ELMs) by Magnetic Perturbations (MP) in low density high confinement mode (H-mode) plasmas are studied in the ASDEX Upgrade tokamak. The main empirical requirements for full ELM suppression in our experiments are: 1. The poloidal spectrum of the MP must be aligned for best plasma response from weakly stable kink-modes, which amplify the perturbation, 2. The plasma edge density must be below a critical value, 3.3×10 19 m −3 . The edge collisionality is in the range ν * i = 0.15 − 0.42 (ions) and ν * e = 0.15 − 0.25 (electrons). However, our data does not show that the edge collisionality is the critical parameter that governs access to ELM suppression. 3. The pedestal pressure must be kept sufficiently low to avoid destabilisation of small ELMs. This requirement implies a systematic reduction of pedestal pressure of typically 30% compared to unmitigated ELMy H-mode in otherwise similar plasmas. 4. The edge safety factor q 95 lies within a certain window. Within the range probed so far, q 95 = 3.5 − 4.2, one such window, q 95 = 3.57 − 3.95 has been identified. Within the range of plasma rotation encountered so far, no apparent threshold of plasma rotation for ELM suppression is found. This includes cases with large cross field electron flow in the entire pedestal region.

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“…In single fluid model, the ω ⊥e is reduced to ω E , which was applied in previous studies [38]. One simple way to mimic two fluid flow effect [27,39] is to employ the ω ⊥e as a flow input for MARS-F.…”

Section: Numerical Models and Equilibrium Setupmentioning

confidence: 99%

“…The dependence of plasma response on rotation zero-crossing is obtained by scanning of rotation profiles for MARS-F modeling [38]. Hyperbolic tangent is employed to construct rotation profiles with assigned zero-crossing applying similar method in Ref.…”

Section: Numerical Models and Equilibrium Setupmentioning

confidence: 99%

Plasma response to resonant magnetic perturbations near rotation zero-crossing in low torque plasmas

Xie,

Sun,

Liu

et al. 2021

Preprint

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Plasma response to resonant magnetic perturbations (RMPs) near the pedestal top is crucial for accessing edge localized modes (ELMs) suppression in tokamaks. Since radial location of relevant rotation zero-crossing plays a key role in determining the threshold for field penetration of RMP, plasma response may be different in low input torque plasma. In this work, the linear MHD code MARS-F is applied to reveal the dependence of plasma response to RMP on rotation zero-crossing by a scan of rotation profiles based on an EAST equilibrium. It is shown that the plasma response is enhanced when zero-crossing occurs near rational surfaces. The dependence of plasma response on the location of rotation zero-crossing is well fitted by a double Gaussian, indicating two effects in this enhancement. One is induced by rotation screening effect shown as a wide base (with a width around 10 − 20 krad/s), and the other is related to resistive singular layer effect characterized by a localized peak (with a width around 3 − 4 krad/s). The peak of each resonant harmonic in plasma response appears always at rotation zero-crossing. The width of the peak scales with the resistive singular layer width. The amplitude of the wide base scales inversely with magnitude of the rotation. The plasma displacement suggests the response is tearing like when zero-crossing is within the singular layer, while it is kink like when zero-crossing is far from the layer. The enhancement of magnetic islands' width at the peak is only around a factor of two, when the absolute value of local rotation is not larger than the characteristic width around 10 − 20 krad/s. It is further confirmed in a modeling of plasma response in an EAST ELM suppression discharge, in which there is a zero-crossing in E × B rotation but not in electron perpendicular rotation. No significant difference in plasma response is obtained using these two rotation profiles. This suggests that the rotation near pedestal top should not be far away from zero but may not be necessary to have zero-crossing for accessing ELM suppression.

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Comparative investigation of ELM control based on toroidal modelling of plasma response to RMP fields

Cited by 52 publications

References 42 publications

Overview of HL-2A recent experiments

Overview of HL-2A recent experiments

Experimental conditions to suppress edge localised modes by magnetic perturbations in the ASDEX Upgrade tokamak

Plasma response to resonant magnetic perturbations near rotation zero-crossing in low torque plasmas

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