Electron cyclotron current drive in the Wendelstein 7-AS stellarator
Electron cyclotron current drive in the Wendelstein 7-AS stellarator
复制标题
Wendelstein 7-AS 仿星器中的电子回旋电流驱动
DOI：
10.1088/0741-3335/47/8/002
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发表时间：
2005
影响因子：
2.2
通讯作者：
N. Marushchenko
中科院分区：
文献类型：
--
作者：
H. Maassberg;M. Romé;V. Erckmann;J. Geiger;H. Laqua;N. Marushchenko
分析了W7-AS仿星器的高功率电子回旋电流驱动（ECCD）实验。在这些无净电流放电中，ECCD和自举电流由感应电流反馈控制。基于测量的密度和温度分布，新古典预测的自举（考虑双极径向电场）和感应电流密度以及ECCD从线性伴随方法与捕获粒子包括计算。对于静止条件，检查电流平衡。描述了在固定密度下的发射角扫描以及在固定发射角下的密度扫描。低频MHD模式的活动得到强co-ECCD，并为反ECCD的“功能”与完全丧失的中心confinition. The线性ECCD预测是在合理的协议与电流平衡，除了低密度放电与高峰值的轴上沉积，其中ECCD从线性理论预测超过了约2倍，从电流平衡。由于自举电流很好地平衡了电感电流无ECCD，线性ECCD高估相比，非线性福克-普朗克（FP）模拟，其中两个不同的功率损耗模型被用来达到稳态。这些体积平均FP模拟不能描述低密度下的ECCD降解。
High power electron cyclotron current drive (ECCD) experiments in the W7-AS stellarator are analysed. In these net-current-free discharges, the ECCD and the bootstrap current are feedback controlled by an inductive current. Based on the measured density and temperature profiles, the neoclassical predictions of the bootstrap (with the ambipolar radial electric field taken into account) and the inductive current densities as well as the ECCD from the linear adjoint approach with trapped particles included are calculated. For stationary conditions, the current balance is checked. Launch-angle scans at fixed density as well as density scans at fixed launch-angle are described. Low-frequency MHD mode activity is obtained for strong co-ECCD, and for counter-ECCD a ‘ feature’ with complete loss of the central confinement is found. The linear ECCD prediction is in reasonable agreement with the current balance except for low-density discharges with highly peaked on-axis deposition, where the ECCD predicted from linear theory exceeds by a factor of about 2 the one from the current balance. Since the bootstrap current is well balanced by the inductive current without ECCD, the linear ECCD overestimate is compared with nonlinear Fokker–Planck (FP) simulations, where two different power loss models are used to reach steady state. These volume-averaged FP simulations cannot describe the ECCD degradation at the low densities.