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

Abstract

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.

Influence of lower hybrid wave injection on peeling-ballooning modes

“…性粒子电离和LHW功率谱中高 的分量等因 素有关. 此外HL-2A [24] 和J-TEXT [25] 中进行了使 用偏压电极驱动刮削层中HCF实验, 在驱动出百 安培刮削层电流的同时可以观察到偏滤器打击点 的分裂, 也为LHW驱动出的HCF可以缓解ELM 提供了强有力的证据. LHW驱动的HCF和主等 离子体电流对P-B模线性和非线性演化的作用机 制仍然没有被完全理解, 因此有必要进一步开展相 关的理论模拟研究工作.…”