Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak
Observation of Efficient Lower Hybrid Current Drive at High Density in Diverted Plasmas on the Alcator C-Mod Tokamak
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DOI：
10.1103/physrevlett.121.055001
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发表时间：
2018-08-03
影响因子：
8.6
通讯作者：
Wukitch, S.
中科院分区：
文献类型：
--
作者：
Baek, S. G.;Wallace, G. M.;Wukitch, S.
在Alcator C-Mod托卡马克装置上，通过增加等离子体电流，从而降低格林沃尔德密度分数，在偏转等离子体中实现了高效率的低杂波电流驱动（LHCD），其密度可达1.5 × 10（20）m（-3）。该密度超过了先前报道的在（n）/bar（e）处的标称“LH密度极限”，约为1.0 x 10（20）m（-3），在此之上观察到电流驱动效率的异常损失。目前的驱动效率恢复到与工程规模一致的水平，与密度肩和湍流水平的减少，在远刮层。同时，射频波与边缘和/或刮削层等离子体的相互作用减少，如在等离子体边缘处测量的波频谱的最小加宽所示。这些结果对维持稳态托卡马克运行具有重要意义，并为在反应堆中实现高效LHCD指明了前进的道路。
Efficient lower hybrid current drive (LHCD) is demonstrated at densities up to (n) over bar (e) approximate to 1.5 x 10(20) m(-3) in diverted plasmas on the Alcator C-Mod tokamak by operating at increased plasma current-and therefore reduced Greenwald density fraction. This density exceeds the nominal "LH density limit" at (n) over bar (e) approximate to 1.0 x 10(20) m(-3) reported previously, above which an anomalous loss of current drive efficiency was observed. The recovery of current drive efficiency to a level consistent with engineering scalings is correlated with a reduction in density shoulders and turbulence levels in the far scrape-off layer. Concurrently, rf wave interaction with the edge and/or scrape-off-layer plasma is reduced, as indicated by a minimal broadening of the wave frequency spectrum measured at the plasma edge. These results have important implications for sustaining steady-state tokamak operation and indicate a pathway forward for implementing efficient LHCD in a reactor.