Pre-disruption MHD activity in the LT-4 tokamak

Cheetham, A.D.; Hamberger, S.M.; Kuwahara, Hiroshi; Morton, A.H.; Vender, D.

doi:10.1088/0029-5515/27/5/013

Cited by 11 publications

(10 citation statements)

References 20 publications

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“…On NSTX, the rotation is varied by the application of n = 3 static magnetic perturba tion, and a stabilizing effect from the rotation shear is found [20]. On JET, the plasma rotation is also found to stabilize the m/n = 3/2 mode [21]. On T10, the frequency and ampl itude of MHD modes are found to be able controlled by a nondisruptive halocurrent [22].…”

Section: Nuclear Fusionmentioning

confidence: 97%

Effect of electrode biasing on m/n = 2/1 tearing modes in J-TEXT experiments

Liu

Chen

et al. 2016

Nucl. Fusion

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The effects of electrode biasing (EB) on the m/n = 2/1 tearing mode have been experimentally studied in J-TEXT tokamak discharges, where m and n are the poloidal and toroidal mode numbers. It is found that for a negative bias voltage, the mode amplitude is reduced, and the mode frequency is increased accompanied by the increased toroidal plasma rotation speed in the counter-I p direction. For a positive bias voltage, the mode frequency is decreased together with the change of the rotation velocity towards the co-I p direction, and the mode amplitude is increased. Statistic results show that the variations in the toroidal rotation speed, the 2/1 mode frequency and its amplitude linearly depend on the bias voltage. The threshold voltages for complete suppression and locking of the mode are found. The experimental results suggest that applied electrode biasing is a possible method for the avoidance of mode locking and disruption.

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Section: Nuclear Fusionmentioning

confidence: 97%

Effect of electrode biasing on m/n = 2/1 tearing modes in J-TEXT experiments

Liu

Chen

et al. 2016

Nucl. Fusion

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“…The output graph is a colour-map image with time and frequency on X and Y axis respectively and the magnitude at each frequency is reflected by a colour code ('JET' type) with colour 'red' representing the highest magnitude and blue being the lowest as shown in the figures later in the text. The magnetic island width is estimated using the following equation [30,34].…”

Section: Discussionmentioning

confidence: 99%

“…The value of ν is taken to be 4 [34] to generate the q profile using an estimated q a . The mode structures are obtained using the singular value decomposition (SVD) technique [30,34].…”

Section: Discussionmentioning

confidence: 99%

Characterization of the plasma current quench during disruptions in ADITYA tokamak

Purohit¹,

Chowdhuri²,

Ghosh³

et al. 2020

Nucl. Fusion

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The rate of plasma current-quench during tokamak plasma disruptions determines the electromagnetic forces on the in-vessel components/vacuum vessel. Also halo currents and rapid changes of poloidal field due to the plasma vertical displacement contribute to loads on vessel and in-vessel components and hence needs to be studied thoroughly to safeguard these tokamak peripherals. The plasma current quench occurrence during the spontaneous major disruption has been investigated for a set of ADITYA tokamak disrupted discharges and average plasma current quench and instantaneous current quench rates have been estimated. The fastest area-normalized plasma current (I P ) quench time is observed to be ∼5 ms m −2 . The estimated post disruption plasma electron temperatures (PDET) are observed to be ∼15-35 eV and proportional to area-normalized plasma current quench time. Further analysis of several disruptive discharges of ADITYA tokamak reveal that the current quench time is inversely proportional to the pre-disruptive values of edge safety factor, q a , and the current quench properties are strongly correlated with the prevailing pre-disruptive plasma magnetohydrodynamic (MHD) activities. For larger values of pre-disruptive q a , the larger island widths of m = 2 and m = 3 MHD modes leads to a significant overlap of these islands. Such an overlap along with the deeper locations of the islands inside the plasma column, as compared to discharges having smaller values of pre-disruptive q a , seems to facilitate the faster current quench.

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“…For high current operation, there is a hard limit imposed by ideal kink modes which are unstable for q edge < 2. In the experiment, the disruption behavior associated with kink or tearing mode instabilities could be observed in the low-q plasma when q edge approaching the value of two [2,3]. Recently researches which focus on disruption avoidance show one of the active feedback control techniques that using small non-axisymmetric magnetic field could suppress these unstable MHD instabilities [4].…”

Section: Introductionmentioning

confidence: 99%

Three-Dimensional Nonlinear Modeling of MHD Instabilities for Low-q Plasma on J-TEXT

Huang

Suzuki

2021

Plasma and Fusion Research

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The characteristics of the magnetohydrodynamics (MHD) instabilities for low edge safety factor (low-q) plasma are investigated on J-TEXT with three-dimensional (3D) nonlinear MHD Infrastructure for Plasma Simulation (MIPs) code. The dynamics of m = 2 mode coupling with m = 1 mode is found in the linear growth phase with the initial q axis < 1 equilibrium. And new 3D helical coils are designed for generating additional rotational transform based on the J-TEXT configuration, which is helpful to suppress the amplitude of the MHD instabilities from the modeling result.

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Pre-disruption MHD activity in the LT-4 tokamak

Cited by 11 publications

References 20 publications

Effect of electrode biasing on m/n = 2/1 tearing modes in J-TEXT experiments

Effect of electrode biasing on m/n = 2/1 tearing modes in J-TEXT experiments

Characterization of the plasma current quench during disruptions in ADITYA tokamak

Three-Dimensional Nonlinear Modeling of MHD Instabilities for Low-q Plasma on J-TEXT

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