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中国物理学会期刊

EAST托卡马克钨杂质上下不对称性分布的实验研究

CSTR: 32037.14.aps.73.20231448

Experimental study on up-down asymmetry of tungsten impurities in EAST tokamak

CSTR: 32037.14.aps.73.20231448
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  • 基于EAST托卡马克装置高性能极紫外空间分辨杂质光谱仪, 本文首次开展了磁约束聚变装置高Z杂质上下不对称分布的实验研究. 实验结果显示, 在同向中性束注入期间, 等离子体芯部环向旋转速度Vt0较大, 钨杂质上下不对称性较强, 且辐射(密度)较强的一侧背离离子B\times \nabla B漂移方向; 当从上外偏滤器充气口注入氘化甲烷气体后, Vt0迅速下降, 原有上下不对称性发生反转. 因此我们针对近似条件下W32+杂质离子特征线辐射不对称因子Iu/IdVt0依赖关系开展了进一步的统计分析. 结果表明, Iu/Id正相关于Vt0, 当Vt0 < 20 km/s以下时, 不对称性发生反转. 上述现象从实验角度验证了漂移动理学的理论预测, 说明环向旋转带来的离心力影响了杂质离子平行于磁场方向的动量守恒, 作为直接诱因, 造成了高Z杂质密度的上下不对称分布, 进而影响辐射的分布. 本文对钨杂质上下不对称性分布的实验观测为进一步开展高Z杂质极向输运的机理研究打下了坚实的基础, 并为今后聚变堆高Z杂质控制提供重要的参考.

     

    By using the high-performance extreme ultraviolet spatial resolution impurity spectrometer, the up-down asymmetric distribution of tungsten impurity radiation in EAST tokamak is studied experimentally for the first time. The results show that during the co-directional neutral beam injection, the central toroidal rotation velocity is large, the up-down asymmetry is strong, and the side with strong radiation deviates from ion B\times \nabla B drift direction. However, after injecting deuterated methane CD4 into plasma through the valve of the upper divertor outer plate, the central toroidal rotation velocity decreases rapidly, and the asymmetry of the original tungsten impurity radiation decreases soon and finally reverses. In this work, a further statistical study of the W32+ impurity radiation asymmetry factor Iu/Id depending on the central toroidal rotation velocity Vt0 is performed. The results show that when Vt0 is larger than 30 km/s, the side with strong radiation deviates from ion B\times \nabla B drift direction, however, when Vt0 decreases to below 20 km/s, the asymmetry can be reversed. The relation of toroidal rotation velocity with impurity radiation asymmetry validates the prediction from drift-kinetic theory, and demonstrates that the centrifugal force induced by the toroidal rotation directly causes the asymmetric distribution of tungsten impurities through affecting the momentum conservation parallel to the magnetic field. The experimental observation of the asymmetric distribution of tungsten impurities in this work lays a solid foundation for further studying the poloidal transport of high-Z impurities and provides some important references for controlling the high-Z impurities in future fusion reactors.

     

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