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题   目: Experimental Validation of a Kinetic Ballooning Mode in DIII-D High Performance High β_p Plasmas

报告人: 简翔,General Atomics

时   间: 2023年05月24日(周三)  下午 14:00 

地   点: 聚变科学所二楼大会议室

摘   要: The presence of kinetic ballooning modes (KBM) has been experimentally validated in the core of high performance, high β_p plasmas, and their significant role in transport and confinement in these plasmas are predicted via quasi-linear estimations. Recent developments in advanced tokamak research on DIII-D have demonstrated the excellent compatibility of a high bootstrap current fraction (f_BS=80%) regime with high confinement (H_(98(y,2))=1.7) and MHD stability(β_N=4.2). Several global parameters of importance to fusion performance (H_(98(y,2)), β_N, f_BS) have reached or exceeded the desired range for some attractive fusion power plant(FPP) designs2, highlighting the relevance of transport physics of such a plasma to the FPP. We report the observation of a set of electromagnetic coherent high frequency fluctuations in such a plasma with the Radial Interferometer Polarimeter. Based on the beam emission spectroscopy diagnostic, the density fluctuations are located in the internal transport barrier (ITB) at large radius (ρ~0.55) and have frequency of 130~220kHz. The poloidal wavelength is estimated to be 17~30m-1 at the outboard midplane with toroidal mode number n~5-9. The poloidal phase velocity of the coherent fluctuations is ~30km/s in the ion diamagnetic direction in the plasma frame at the outboard midplane. They are experimentally validated to be KBMs by various metrics, including mode dispersion relation, toroidal mode number and mode location etc. Quasi-linear estimation using CGYRO predicts that the KBM can drive experimental relevant particle flux and non-negligible thermal flux, suggesting its significant role in the ITB saturation and the global plasma performance.

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