Experimental impurity transport and theoretical interpretation in a Tore Supra lower-hybrid heated plasma
Experimental impurity transport and theoretical interpretation in a Tore Supra lower-hybrid heated plasma
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DOI：
10.1088/0741-3335/50/5/055010
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发表时间：
2008-05
影响因子：
2.2
通讯作者：
T. Parisot;R. Guirlet;C. Bourdelle;X. Garbet;N. Dubuit;F. Imbeaux;P. Thomas
中科院分区：
文献类型：
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作者：
T. Parisot;R. Guirlet;C. Bourdelle;X. Garbet;N. Dubuit;F. Imbeaux;P. Thomas
最近的数值工作湍流杂质输运提出了一个新的兴趣，在杂质输运的实验研究，更特别是其参数依赖性与理论预测的比较。在这种情况下，我们研究了四种不同的杂质物种在Tore上低混合加热，锯齿形的等离子体的行为。我们观察到在探索的范围内（从13到32），随着Z的增加，中心杂质限制时间τimp减小。这一结果与新古典理论和湍流理论的预测都相矛盾。一维杂质输运代码ITC的分析表明，存在一个中心区，减少扩散和指示的向内对流。这些结果完成了新古典运输（NCLASS）和湍流运输的准线性gyrokinetic的LiKiz和非线性gyrofluid TRB模型的理论模拟。这些模拟不提供对杂质电荷的约束时间依赖性的解释。非线性湍流计算很好地描述了r/a = 0.3以外的传输，但中心区域预计低于湍流阈值，而观察到的传输比新古典值高一个数量级。回旋动力学的计算证明了曲率箍缩在总对流通量中的主导作用。这个术语是向内的，并且仅弱依赖于所探索的物种范围内的杂质电荷。
Recent numerical works on turbulent impurity transport raise a new interest in experimental studies on impurity transport and more especially a comparison of its parametric dependences with theoretical predictions. In this context, we have studied the behaviour of four different impurity species in Tore Supra lower-hybrid heated, sawtooth-free plasmas. We observe a decrease in the central impurity confinement time τimp with increasing Z in the range explored (from 13 up to 32). This result is in contradiction to both neoclassical and turbulent theoretical predictions. An analysis with the 1D impurity transport code ITC shows the existence of a central zone with reduced diffusion and indication of an inward convection. These results are completed with theoretical simulations of neoclassical transport (NCLASS) and turbulent transport with the quasilinear gyrokinetic QuaLiKiz and nonlinear gyrofluid TRB models. These simulations do not provide an explanation of the confinement time dependence on the impurity charge. Transport outside r/a = 0.3 is well described by the nonlinear turbulent calculations but the central region is predicted to be below the turbulence threshold while the observed transport is one order of magnitude higher than neoclassical values. The gyrokinetic calculations evidence the dominant role of the curvature pinch in the total convective flux. This term is directed inwards and only weakly dependent on the impurity charge in the explored range of species.