Influence of rotating resonant magnetic perturbations on particle confinement

Hu, Qiming; Yu, Q.; Wang, Nengchao; Shi, Peng; Yi, Bin; Ding, Yonghua; Ren, Bo; Chen, Zhipeng; Gao, Li; Hu, Xiwei; Jin, Hai; Mao, Li; Li, Jianchao; Yu, Kexun; Zhuang, G.

doi:10.1088/0029-5515/54/12/122006

Cited by 17 publications

(23 citation statements)

References 34 publications

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“…The global increase of the electron density well after the field penetration might also be associated the enhanced edge recycling. For rotating RMPs with a large 3/1 component, the increased electron density is consistent with previous finding that a sufficiently high rotating frequency of RMPs increases the electron density [33], but the enhanced edge recycling might also play a role here.…”

Section: Discussion and Summarysupporting

confidence: 92%

Plasma response to m/n = 3/1 resonant magnetic perturbation at J-TEXT Tokamak

Wang

et al. 2016

Nucl. Fusion

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The influence of resonant magnetic perturbations (RMPs) with a large m/n = 3/1 component on electron density has been studied on J-TEXT tokamak by using externally applied static and rotating RMPs, where m and n are the poloidal and toroidal mode number, respectively. The detailed time evolution of electron density profile, measured by the polarimeter-interferometer, shows that the electron density ne first increases (decreases) inside (around/outside) of the 3/1 rational surface (RS), and it is increased globally later together with enhanced edge recycling. Associated with field penetration, the toroidal rotation around the 3/1 RS is accelerated in co-Ip direction and the poloidal rotation is changed from electron to ion diamagnetic drift direction. Spontaneous unlocking-penetration circles occur after field penetration if the RMPs amplitude is not strong enough. While for sufficiently strong RMPs, the 2/1 locked mode is also triggered due to mode coupling, and the global density is increased. The field penetration threshold is found to be linearly proportional to the neL (line-integrated density) at the 3/1 RS but to (neL) 0.73 for the ne at plasma core. In addition, for rotating RMPs with a large 3/1 component, field penetration causes global increase in electron density.

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Section: Discussion and Summarysupporting

confidence: 92%

Plasma response to m/n = 3/1 resonant magnetic perturbation at J-TEXT Tokamak

Wang

et al. 2016

Nucl. Fusion

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“…20 The TM1 model solves for the balance between the electromagnetic (EM) torque and the plasma viscosity, which governs the threshold for resonant field penetration, and also solves for the enhanced transport produced by resonant field penetration. Previously TM1 studies explored resonant field penetration in the core of TEXTOR, 25 DIII-D 26 and J-TEXT 27 tokamaks in the context of large-scale (m/n = 2/1) tearing and locked modes. A description of the TM1 code and coupling with GPEC is provided in the supplemental material.…”

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confidence: 99%

Multi-diagnostic analysis of plasma filaments in the island divertor

Zoletnik

Anda

Biedermann

et al. 2019

Plasma Phys. Control. Fusion

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Filaments or blobs are well known structures in turbulence in magnetic fusion devices, they are considered to be the major cross-transport channel in the scrape off layer. They originate at the last closed magnetic flux surface and propagate out on the low field side of toroidal devices due to polarization in the curved magnetic field. The Wendelstein 7-X stellarator has a complex three-dimensional magnetic field structure and additionally the plasma is bounded by a chain of magnetic islands, forming an island divertor. After the first observation of filaments in Wendelstein 7-X with video cameras a multi-diagnostic study is presented in this paper to reveal their 3D structure and dynamics. Filaments are seen to be born at the edge and, at least in some cases, seen to extend to up to 4 toroidal turns. After moving radially out a few cm they enter the edge island. Here they disappear from the equatorial plane and about 200 microseconds later reappear on the outboard side of the island. A long-wavelength (∼20–30 cm) quasi coherent mode is observed in both regions where filaments appear. The similarities and differences between the filaments seen in W7-X and other devices are discussed. Possible explanations for this strange radial propagation are considered, together with the likely role of filaments in the edge and island density profile.

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“…3. In this discharge, the 2/1 TM, originally rotating at 3.2 kHz, was accelerated to 6 kHz at 0.26 s due to the application of a 6 kHz RRMP [24,43]. Due to some reasons which remain to be investigated, the TM unlocked from the 6 kHz RRMP at 0.3 s. Then the TM slowed down as indicated by the decrease of f TM (Fig.…”

Section: Plasma Response To Rrmp With a Quasi-static Tmmentioning

confidence: 96%

“…The RRMP coils can induce eddy currents in the wall and the corresponding attenuation effect saturates above 1 kHz. b r 2/1 , calculated at r = a, is 0.45 ~ 0.55 Gauss/kA for the RRMP field in the frequency range of 1 ~ 6 kHz [40,43]. For the RRMP, δ 2/1 = 2πf RRMP t + δ 0 2/1 , where δ 0 2/1 is the phase of RRMP at t = 0.…”

Section: Experimental Set-upmentioning

confidence: 99%

Plasma response to rotating resonant magnetic perturbations with a locked mode in the J-TEXT tokamak

Wang¹,

Ren²,

et al. 2019

Nucl. Fusion

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Disruption caused by locked modes (LMs) is one of the most critical issues to be solved for tokamak fusion reactors. This paper aimed to understand the plasma response to external rotating resonant magnetic perturbations (RMPs), which are applied at a few kilohertz for controlling the pre-existing LMs. In the J-TEXT tokamak, the plasma response to a rotating RMP showed a feature of travelling wave, if no tearing mode (TM) existed. With a LM, the application of a rotating RMP led to unique features of plasma responses, which could be roughly described by the formula δb θ (θ, t) = 2Asin(mθmθ O)cos(2πf RRMP t), where δb θ , A, m, θ O and f RRMP are the perturbed poloidal magnetic field, the amplitude, the poloidal mode number, the poloidal location of the TM's O-point and the frequency of the rotating RMP. These features are analogous to that of a standing wave in the TM rest frame, with the nodes locating at the O-/X-points. The perturbations of electron temperature, T e , due to plasma responses were zero or minimal inside the magnetic island or outside the magnetic island but at the same poloidal positions as the O-/X-points. Both δb θ and the T e perturbations increased linearly with the rotating RMP. A phenomenological model is proposed that the rotating RMP drives the phase oscillation of the TM by applying a periodical electromagnetic torque. Then the phase oscillation of TM, combined with the poloidal gradient of the plasma parameters, induces the plasma response measured experimentally. The nonlinear numerically modelling confirmed the forced phase oscillation of the TM, and qualitatively verified the amplitude and phase dependences among the plasma response, the phase oscillation of the TM and the rotating RMP, which have been predicted by the model.

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Influence of rotating resonant magnetic perturbations on particle confinement

Cited by 17 publications

References 34 publications

Plasma response to m/n = 3/1 resonant magnetic perturbation at J-TEXT Tokamak

Plasma response to m/n = 3/1 resonant magnetic perturbation at J-TEXT Tokamak

Multi-diagnostic analysis of plasma filaments in the island divertor

Plasma response to rotating resonant magnetic perturbations with a locked mode in the J-TEXT tokamak

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