Application of very high harmonic fast waves for off-axis current drive in the DIII-D and FNSF-AT tokamaks
Application of very high harmonic fast waves for off-axis current drive in the DIII-D and FNSF-AT tokamaks
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DOI：
10.1088/0029-5515/54/8/083024
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发表时间：
2014-06
期刊：
影响因子：
3.3
通讯作者：
R. Prater;C. Moeller;R. Pinsker;M. Porkolab;O. Meneghini;V. Vdovin
中科院分区：
文献类型：
--
作者：
R. Prater;C. Moeller;R. Pinsker;M. Porkolab;O. Meneghini;V. Vdovin
频率远高于离子回旋加速器频率并接近较低混合频率的快波（也称为“螺旋”或“口哨”）可应用于具有高电子β的托卡马克中的离轴电流驱动。高频导致波功率的类似口哨的行为几乎沿着场力线，但具有较小的径向分量，因此波缓慢地螺旋向等离子体中心。高频也有助于强大的阻尼。模型预测，当电子 beta 高于约 1.8% 时，与 DIII-D 和聚变核科学设施 (FNSF) 中高性能放电的替代方案相比，具有良好效率的强大离轴电流驱动。射线行为的详细分析表明，射线轨迹和阻尼是确定性的（即，不受等离子体轮廓或初始射线条件的强烈影响），这与低频快波实验中的混沌射线行为不同。发现电流驱动对平行折射率n′的发射值不敏感，因此可以减少波可达性问题。使用行波天线可提供非常窄的 n 频谱，这也有助于避免可达性问题。
Fast waves at frequencies far above the ion cyclotron frequency and approaching the lower hybrid frequency (also called 'helicons' or ‘whistlers’) have application to off-axis current drive in tokamaks with high electron beta. The high frequency causes the whistler-like behaviour of the wave power nearly following field lines, but with a small radial component, so the waves spiral slowly towards the plasma centre. The high frequency also contributes to strong damping. Modelling predicts robust off-axis current drive with good efficiency compared to alternatives in high performance discharges in DIII-D and Fusion Nuclear Science Facility (FNSF) when the electron beta is above about 1.8%. Detailed analysis of ray behaviour shows that ray trajectories and damping are deterministic (that is, not strongly affected by plasma profiles or initial ray conditions), unlike the chaotic ray behaviour in lower frequency fast wave experiments. Current drive was found to not be sensitive to the launched value of the parallel index of refraction n‖, so wave accessibility issues can be reduced. Use of a travelling wave antenna provides a very narrow n‖spectrum, which also helps avoid accessibility problems.