An experimental investigation of blob behaviors in lower hybrid wave dominant heating scenarios on EAST

Wang, Qian; Hu, G.H.; Sheng, Zheng-Mao; Niu, Y.; Wang, H. Q.; Xu, G. S.; Chen, R.; Yang, Qingquan; Wang, Y. F.

doi:10.1063/1.5093790

Cited by 5 publications

(4 citation statements)

References 46 publications

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“…In the EAST tokamak, blob statistical characteristics [29] and blob properties in the lower hybrid wave dominant heating discharges [30] have been reported in previous work. However, the blob transition with the line-averaged density phenomenon has not yet been studied on EAST.…”

Section: Introductionsupporting

confidence: 66%

Experimental investigation of scrape-off layer blob high density transition in L-mode plasmas on EAST

WANG¹,

Hu²,

Yan³

et al. 2022

Plasma Sci. Technol.

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Lithium Beam Emission Spectroscopy (Li-BES) system in the outer midplane and divertor Langmuir probe arrays embedded in the divertor target plates, are utilized to investigate the scrape-off layer (SOL) blob transition and its relation with divertor detachment on EAST. The blob transition in the near SOL is observed during the density ramp-up phase. When the plasma density normalized to the Greenwald density limit exceeds a threshold of fGW ~ 0.5, the blob size and lifetime increases by 2‒3 times while the blob detection rate decreases by about 2 times. In addition, a weak density shoulder is observed in the near SOL region at the same density threshold. Further analysis indicates that the divertor detachment is highly correlated with the blob transition, the density threshold of blob transition is consistent with that of the access to outer divertor detachment. The potential physical mechanisms has been discussed. These results could be useful for the understanding of plasma-wall interaction (PWI) issues in future devices that will operate under detached divertor and high density (over the blob transition threshold) conditions.

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Section: Introductionsupporting

confidence: 66%

Experimental investigation of scrape-off layer blob high density transition in L-mode plasmas on EAST

WANG¹,

Hu²,

Yan³

et al. 2022

Plasma Sci. Technol.

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“…(b) The modification of E r might influence the SOL turbulence. It is observed from the experiments on EAST using LHW and on TORPEX using EBs that the blob can be controlled [29,47]. Besides, the EAST experiments suggest that the E r × B flow shear plays an important role in blob suppression.…”

Section: The Impact Of the Sol Current On The Plasma Parametersmentioning

confidence: 96%

Impact of the non-axisymmetric SOL current driven by a biased electrode on the diverted J-TEXT plasma

Wang

Ding

et al. 2022

Plasma Phys. Control. Fusion

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It is observed in EAST that the non-axisymmetric helical currents induced by lower hybrid waves (LHW) in the scrape-off layer (SOL) can produce resonant magnetic perturbations (RMPs), hence mitigate edge-localized modes (ELMs) significantly and cause the strike points splitting. In this work, the NA-SOL current driven by an alternative method, i.e. biased electrode, is shown to influence the plasma boundary, especially the strike points, in the divertor configuration on J-TEXT. With positive bias to the electrode, the upper strike points on the divertor target plate is observed to split as captured by the visible camera. Such splitting is usually observed with the RMPs. In addition, the SOL plasma parameters measured by the reciprocating probe, such as floating potential (Vf), electron temperature (Te), and ion saturation current (Is), are significantly altered by applying modulation bias, which is closely related to the SOL current. A SOL current model has been extended from the limiter configuration version to the poloidal divertor configuration, and the magnetic field generated by SOL current and the change of magnetic topological structure of plasma boundary can be simulated. The simulation results shows that the magnetic perturbation generated by the SOL current can induce the lobes near the X-point, which is three-dimensional asymmetric structure, and shows good agreement with the experimental observation. The active control of the boundary magnetic topology indicates that the SOL current is capable of generating strong magnetic perturbations, and hence might be sufficient for the control of ELMs.

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“…EAST is a medium-size superconducting tokamak aiming for long-pulse steady-state highperformance operation with major radius 𝑅 ∼ 1.88 m and minor radius a ∼ 0.45 m. Li-BES diagnostic has been put into operation since 2014 on EAST [8], which has been successfully applied to measurements of density profiles [9], edge turbulence [10][11][12], and scrape off layer (SOL) blobs [13]. However, there are some problems and shortcomings as follows.…”

Section: Introductionmentioning

confidence: 99%

Beam optics simulation of the ion injector for sodium Beam Emission Spectroscopy (Na-BES) on EAST

Wang

et al. 2023

J. Inst.

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To upgrade the Li-BES to Na-BES on Experimental Advanced Superconducting Tokamak (EAST), a high-brightness and stable sodium (Na) ion source is developed, and the performance of Na ion beam optics is simulated by the COMSOL Multiphysics. The porous tungsten disk with 70% porosity and filled with albite Na2O·Al2O3·6SiO2 is successfully developed as the Na ion source. The extracted current density of the Na-beam increases with the extraction voltage, and its maximum current can reach 9 mA with the ion source diameter of 20 mm. The lifetime of the Na ion source is evaluated to be 63 mAh, which is much longer than that of the Li ion source. The simulation shows that the preferable distances among the ion source (or anode electrode), extractor and puller to get the well-focused beam are x puller - x extractor ∼ 0.06 m and x extractor - x ion source ∼ 0.02 m. Further simulation with these optimized distances determines the extraction voltage and ion source size for good beam performance. In addition, the simulation shows the beam divergence angle decreases by more than 40% by optimizing the Einzel voltage to 5 kV, suggesting an excellent focusing property of the Einzel lens. These works provide the basis and the design references for the Na-BES development on EAST.

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An experimental investigation of blob behaviors in lower hybrid wave dominant heating scenarios on EAST

Cited by 5 publications

References 46 publications

Experimental investigation of scrape-off layer blob high density transition in L-mode plasmas on EAST

Experimental investigation of scrape-off layer blob high density transition in L-mode plasmas on EAST

Impact of the non-axisymmetric SOL current driven by a biased electrode on the diverted J-TEXT plasma

Beam optics simulation of the ion injector for sodium Beam Emission Spectroscopy (Na-BES) on EAST

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