Impurity transport driven by parallel velocity shear turbulence in hydrogen isotope plasmas
Impurity transport driven by parallel velocity shear turbulence in hydrogen isotope plasmas
复制标题
氢同位素等离子体中平行速度剪切湍流驱动的杂质传输
DOI：
10.1088/1741-4326/ab1967
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发表时间：
2019-05
期刊：
影响因子：
3.3
通讯作者：
Zhuang Ge
中科院分区：
文献类型：
--
作者：
Guo Weixin;Wang Lu;Zhuang Ge
利用回旋运动理论，在具有弱磁剪切的平板结构中，研究了氢同位素等离子体中由平行速度剪切 (PVS) 湍流驱动的湍流杂质输运。分析得出以扩散和对流形式表示的准线性杂质通量。研究发现PVS湍流会导致向内的杂质对流。对于来自氘（D）和氚（T）反应的高温氦灰，湍流杂质通量可能是向外的，因为杂质扩散比向内对流占主导地位。因此，PVS 湍流可能有利于去除未来燃烧等离子体中的高温氦灰。此外，增加PVS会增强氦灰的向外通量和扩散率，但会降低氦灰的温度，从而降低氦灰的向外通量和扩散率。对于有限浓度的完全电离的轻杂质和微量重金属杂质，剪切平行速度越强，平行速度剖面越陡，杂质积累越严重。因此，PVS 湍流可能是对中性束加热等离子体中杂质积累实验观察的部分解释。同时，电子密度梯度的增加可能有利于稳定PVS模式并缓解等离子体-壁相互作用或外部注入引起的杂质积累。此外，同位素效应（增加有效氢同位素质量数）有利于去除氦灰和减轻PVS湍流引起的重金属杂质的积累。讨论了这些理论结果对未来燃烧等离子体的更多影响。
Turbulent impurity transport driven by parallel velocity shear (PVS) turbulence in hydrogen isotope plasmas is studied using the gyrokinetic theory in a slab configuration with weak magnetic shear. The quasi-linear impurity flux written in terms of diffusion and convection is analytically derived. It is found that PVS turbulence leads to an inward impurity convection. For high temperature helium ash from deuterium (D) and tritium (T) reaction, the turbulent impurity flux could be outward because the impurity diffusion dominates over the inward convection. Therefore, PVS turbulence might be beneficial for removing high temperature helium ash in future burning plasmas. Moreover, both the outward flux and diffusivity of helium ash are enhanced by increasing PVS, but reduced by decreasing the temperature of helium ash. For fully ionized light impurities with finite concentration and the trace heavy metal impurities, the stronger sheared parallel velocity as well as the steeper parallel velocity profile, the more serious accumulation of impurity. Thus, PVS turbulence might be a partial explanation for experimental observation of impurity accumulation in the neutral beam heated plasmas. While, the increase of the electron density gradient may be favorable for stabilizing the PVS mode and easing the accumulation of impurities from plasma-wall interaction or external injection. Furthermore, isotopic effects (increasing the effective hydrogen isotope mass number) are favorable for both removing helium ash and easing the accumulation of heavy metal impurities induced by PVS turbulence. More implications of these theoretical results to the future burning plasmas are discussed.
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