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Double-peaked distribution (DPD) of particle flux has only been observed on the outer divertor target in electron cyclotron resonance heating deuterium plasmas with B × ∇ B toward the X-point in the HL-2A tokamak using high spatiotemporal Langmuir probe arrays. The experimental results demonstrate that the formation of the DPD is mainly due to the enhanced poloidal E × B drift flow stimulated in the divertor region, which is dependent on the plasma density, heating power, and divertor structure. The experimental results are qualitatively consistent with the SOLPS simulation. The experiment also shows that the formation of the DPD might be related to the enhanced cross field transport in the far scrape-off layer. This experimental findings presented here reveal the crucial role played by the synergistic effect of poloidal E × B drift flow and the closed divertor structure in the redistribution of the particle flux, which provides a potential way for the control of high heat flux in future fusion devices. [ABSTRACT FROM AUTHOR]

The effects of a coherent mode (CM) at a frequency of f = 13–16 kHz on the redistribution of divertor particle flux have been studied in HL-2A H-mode plasmas using multiple diagnostics. The experimental results demonstrate that a CM localized at the middle of the pedestal results in outward particle transport, limiting the growth of the pedestal density gradient in the recovery phase of the pedestal, leading to a substantial increase in the localized particle flux striking the outer divertor target, which clearly deviates from the primary peak at the strike point. These observations indicate that the CM might play a crucial role in redistributing the divertor particle flux, which is important for understanding and controlling the divertor heat flux in future fusion-relevant devices. [ABSTRACT FROM AUTHOR]

The inward transport flux accompanied by the long-lived mode (LLM) has been observed by the edge Langmuir probe array during the L-H transition in the HL-2A tokamak. The cross phase between the poloidal electric field fluctuation and the electron density fluctuation in the LLM frequency changed greatly during the L-H transition, which led to the radial transport flux in the LLM frequency to change its transport direction in a given radial region near the pedestal barrier. By using the long distance correlation method, the phase shift of poloidal electric field fluctuation proved to be the key reason, which led to the cross-phase term to change in the LLM frequency. Furthermore, the shear effect has a mode-selecting characteristic on the LLM and turbulence because the direction of turbulent transport still remains radially outward during the H-mode. In addition, when the inward conducted heat flux accompanied by LLM occurs, the poloidal electric field fluctuation and electron temperature fluctuation both have a positive gradient in the LLM frequency; this may indicate that the positive gradient of radial velocity and electron temperature in the LLM frequency play an important role during the entire transport direction change process. [ABSTRACT FROM AUTHOR]