Observations on the W-transport in the core plasma of JET and ASDEX Upgrade
Observations on the W-transport in the core plasma of JET and ASDEX Upgrade
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DOI：
10.1088/0741-3335/55/12/124036
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发表时间：
2013-12
影响因子：
2.2
通讯作者：
T. Pütterich;R. Dux;R. Neu;M. Bernert;M. Beurskens;V. Bobkov;S. Brezinsek;C. Challis;J. Coen
中科院分区：
文献类型：
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作者：
T. Pütterich;R. Dux;R. Neu;M. Bernert;M. Beurskens;V. Bobkov;S. Brezinsek;C. Challis;J. Coen
通过对软x射线相机信号的模拟，推导出w浓度分布，研究了JET核心等离子体中的w输运。在纯中性束加热的情况下，在锯齿状碰撞之间，W在核心的积累（r/a < 0.3）接近10−3的W浓度，这使W剖面变平，浓度约为3 × 10−5。当中心离子回旋加速器共振加热时，核心w浓度呈相位衰减，表现出模式活度的变化，同时电子温度升高，密度曲线变弱。磁流体动力学（MHD）的变化与等离子体核心W的去除之间的直接相关性支持了MHD活动的变化是输运变化的根本原因的假设。此外，对ASDEX升级的放电进行了调查。在这种情况下，等离子体剖面只表现出很小的变化，而最显著的变化发生在受限等离子体的w含量，这是由于燃料氘气体的减少引起的。同时，核心等离子体中的w浓度曲线r/a < 0.2变陡，这让人想起了在w积累强烈的情况下，中心辐射与输运之间众所周知的联系，而在本分析中，在w积累开始时，两者之间的因果关系无法确定。这两个例子都表明，等离子体核心参数的微小变化会极大地影响等离子体核心中的w输运。
The W-transport in the core plasma of JET is investigated experimentally by deriving the W-concentration profiles from the modelling of the signals of the soft x-ray cameras. For the case of pure neutral beam heating W accumulates in the core (r/a < 0.3) approaching W-concentrations of 10−3 in between the sawtooth crashes, which flatten the W-profile to a concentration of about 3 × 10−5. When central Ion cyclotron resonant heating is additionally applied the core W-concentration decays in phases that exhibit a changed mode activity, while also the electron temperature increases and the density profile becomes less peaked. The immediate correlation between the change of magnetohydrodymanic (MHD) and the removal of W from the plasma core supports the hypothesis that the change of the MHD activity is the underlying cause for the change of transport. Furthermore, a discharge from the ASDEX Upgrade is investigated. In this case the plasma profiles exhibit small changes only, while the most prominent change occurs in the W-content of the confined plasma caused by the reduction of the fuelling deuterium gas puff. Concomintantly, the W-concentration profiles in the core plasma r/a < 0.2 steepen up reminescent to the well-known connection between central radiation and transport during cases with strong, established W-accumulation, while in the present analysis such a causality between the two during the onset of W-accumulation could not be pinned down. Both case studies exemplify that small changes of the core parameters of a plasma my influence the W-transport in the plasma core drastically.