Introduction to resonant magnetic perturbation coils of the J-TEXT Tokamak

Ren, Bo; Wang, G.; Ding, Yonghua; Yu, Kun; Li, Q.L.; Wang, N.C.; Yi, Bin; Nan, Jiajun; Cen, Yishun; Hu, Qiming; Jin, Wei; Li, J.C.; Jin, Hai; Zhang, M.; Zhuang, G.

doi:10.1016/j.fusengdes.2014.03.038

Cited by 72 publications

(62 citation statements)

References 15 publications

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“…The plasma parameters for the experiments are the toroidal magnetic field Bt = 1.5-2.0 T, the plasma current Ip = 150-180 kA, the line averaged electron density Ne = 1-3X10 19 m -3 , and the edge safety factor qa = 3.2-4.3. A set of coils, called a dynamic RMP, has been installed inside the vessel on J-TEXT to study the interaction between helical perturbations and magnetized plasmas, and explore a possible method for control of tearing modes [34]. In the present study, the static configuration of RMP was used.…”

Section: Experiments Setupmentioning

confidence: 99%

Plasma flows and fluctuations with magnetic islands in the edge plasmas of J-TEXT tokamak

et al. 2015

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Abstract:The first comprehensive measurements of plasma flows and fluctuations nearby static magnetic islands driven by resonant magnetic perturbations (RMPs) are presented.These experiments were performed using multiple Langmuir probe arrays in the edge plasmas of the J-TEXT tokamak. The effects of controlled variations of the island size and location are explored. This study aims to understand the interaction between turbulence and magnetic islands, and to elucidate magnetic island effects on edge turbulence and flow intensity profiles, edge electric fields, and thus confinement regime transitions. Turbulence and low frequency flows (LFFs) all drop inside the magnetic island, but increase at its boundary, as island width increases. The geodesic acoustic mode (GAM) is damped in most of the edge area with magnetic islands. The sign of the radial electric field changes from negative to positive within 2 the islands. The gradient of turbulent stresses vanishes at island center, and becomes steeper at the boundary of the islands. The particle transport induced by the turbulence is reduced inside the magnetic islands. The magnetic island effects on flows and turbulence can lead to an increase in LFFs and enhance Reynolds stresses near the last closed flux surface (LCFS). A stronger radial electric field layer can be formed near the LCFS when magnetic islands are present. The results suggest that magnetic islands can be used as a tool to enhance edge turbulence and flows, edge electric fields, and thus to trigger confinement regime transitions.

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Section: Experiments Setupmentioning

confidence: 99%

Plasma flows and fluctuations with magnetic islands in the edge plasmas of J-TEXT tokamak

et al. 2015

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“…In this paper, the plasmas were operated with a = 26 cm, the toroidal field B t = 1.58 T, the plasma current I p = 160 kA, and the edge safety factor q a = 3.15. A set of out-vessel RMP coils [40] was used to apply a 2/1 static RMP (SRMP) field to lock the rotating 2/1 TM, while the RRMP fields were also applied to study the plasma response to RMP field by feeding AC currents into the in-vessel RMP coils [40,41], also named the dynamic-RMP (DRMP) or RRMP coils. In the J-TEXT Ohmic plasmas, the 2/1 tearing modes are observed to rotate only in the electron diamagnetic drift direction.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…The distribution of the m/n = 2/1 RMP field can then be expressed as b r 2/1 ×cos(ξ + δ 2/1 ) for the SRMP, the RRMP and the error field, where b r 2/1 and δ 2/1 represent the amplitude and phase of 2/1 RMP field. δ 2/1 is constant and b r 2/1 = 0.55 Gauss/kA at r = a, for the SRMP applied in this paper [40].…”

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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“…On J-TEXT tokamak, two sets of coils have also been developed to study RMP relevant physics. 21 With POLARIS diagnostic, detailed information for both plasma equilibrium response and magnetic perturbation during the RMP can be obtained.…”

Section: Resonant Magnetic Perturbation Penetrationmentioning

confidence: 99%

High resolution polarimeter-interferometer system for fast equilibrium dynamics and MHD instability studies on Joint-TEXT tokamak (invited)

Chen

Zhuang

et al. 2014

Review of Scientific Instruments

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A high-performance Faraday-effect polarimeter-interferometer system has been developed for the J-TEXT tokamak. This system has time response up to 1 μs, phase resolution < 0.1° and minimum spatial resolution ∼15 mm. High resolution permits investigation of fast equilibrium dynamics as well as magnetic and density perturbations associated with intrinsic Magneto-Hydro-Dynamic (MHD) instabilities and external coil-induced Resonant Magnetic Perturbations (RMP). The 3-wave technique, in which the line-integrated Faraday angle and electron density are measured simultaneously by three laser beams with specific polarizations and frequency offsets, is used. In order to achieve optimum resolution, three frequency-stabilized HCOOH lasers (694 GHz, >35 mW per cavity) and sensitive Planar Schottky Diode mixers are used, providing stable intermediate-frequency signals (0.5-3 MHz) with S/N > 50. The collinear R- and L-wave probe beams, which propagate through the plasma poloidal cross section (a = 0.25-0.27 m) vertically, are expanded using parabolic mirrors to cover the entire plasma column. Sources of systematic errors, e.g., stemming from mechanical vibration, beam non-collinearity, and beam polarization distortion are individually examined and minimized to ensure measurement accuracy. Simultaneous density and Faraday measurements have been successfully achieved for 14 chords. Based on measurements, temporal evolution of safety factor profile, current density profile, and electron density profile are resolved. Core magnetic and density perturbations associated with MHD tearing instabilities are clearly detected. Effects of non-axisymmetric 3D RMP in ohmically heated plasmas are directly observed by polarimetry for the first time.

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Introduction to resonant magnetic perturbation coils of the J-TEXT Tokamak

Cited by 72 publications

References 15 publications

Plasma flows and fluctuations with magnetic islands in the edge plasmas of J-TEXT tokamak

Plasma flows and fluctuations with magnetic islands in the edge plasmas of J-TEXT tokamak

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

High resolution polarimeter-interferometer system for fast equilibrium dynamics and MHD instability studies on Joint-TEXT tokamak (invited)

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