Study of impurity transport in FTU ITB plasmas
Study of impurity transport in FTU ITB plasmas
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DOI：
10.1088/0741-3335/46/2/005
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发表时间：
2004-02
影响因子：
2.2
通讯作者：
L. Carraro;L. Gabellieri;M. Mattioli;M. Finkenthal;K. Fournier;M. Leigheb;M. Puiatti;P. Scarin;M. Valisa;D. Pacella
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文献类型：
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作者：
L. Carraro;L. Gabellieri;M. Mattioli;M. Finkenthal;K. Fournier;M. Leigheb;M. Puiatti;P. Scarin;M. Valisa;D. Pacella
用一维含时输运模型研究了FTU电子内输运势垒(ITB)放电过程中的杂质输运，再现了等离子体线发射和连续发射。在两个不同的实验框架中研究了杂质的行为，其中ITB的形成和维持是在FTU中获得的。在第一种情况下，低杂波和电子回旋共振热波是在电流平顶阶段发射的，而在第二种情况下，射频功率是在电流上升阶段早期注入的。正如在欧姆情况下所发现的那样，势垒内的扩散系数增加了10倍，向内收缩速度随着半径增加到3.5m S−1线性增加，才能重现第一种情况下的FTU等离子体发射。必须假定势垒内的扩散系数降低(降低2倍)和大致相同的向内收缩速度(在这种情况下，v(A)=5m S−1)，以解释在Ip上升阶段注入射频功率时的杂质行为。这些扩散系数分布与Jetto程序预测的离子热扩散系数分布相似：对于平顶ITB情况，预测中心电子热导率改善，但离子热导率下降，而中心电子热导率改善，势垒内离子扩散略有改善，导致ITB上升。
Impurity transport during FTU electron internal transport barrier (ITB) discharges has been studied by means of a one-dimensional time dependent transport model to reproduce plasma line and continuum emissions. The impurity behaviour has been explored in two different experimental frames in which the formation and maintenance of an ITB is obtained in FTU. In the first scenario the lower hybrid and electron cyclotron resonance heating waves are launched during the current (Ip) flat-top phase, while in the second scenario the RF power is injected early during the Ip ramp-up phase.A diffusion coefficient enhanced inside the barrier, by a factor of 10, and an inward pinch velocity linearly increasing with the radius up to 3.5 m s−1, as found in the Ohmic case, are necessary to reproduce FTU plasma emission in the first scenario. A diffusion coefficient lowered inside the barrier (by a factor of 2) and about the same inward pinch velocity (v(a) = 5 m s−1 in this case) have to be assumed to interpret the impurity behaviour if the RF power is injected during the Ip ramp-up phase. These diffusion coefficient profiles are similar to the ion thermal diffusivity profiles predicted by the JETTO code: an improved electron thermal conductivity at the centre but degraded ion thermal conductivity is predicted for the flat-top ITB case, while improved electron thermal conductivity in the centre with a slightly improved ion diffusion inside the barrier results in the ramp-up ITB.