Stationary QH-mode plasmas with high and wide pedestal at low rotation on DIII-D
Stationary QH-mode plasmas with high and wide pedestal at low rotation on DIII-D
复制标题
DOI：
10.1088/0029-5515/57/2/022007
复制
发表时间：
2017-02
期刊：
影响因子：
3.3
通讯作者：
Xi Chen;K. Burrell;T. Osborne;W. Solomon;K. Barada;A. Garofalo;R. Groebner;N. Luhmann;G. McKee;C. Muscatello;M. Ono;C. Petty;M. Porkolab;T. Rhodes;J. Rost;P. Snyder;G. Staebler;B. Tobias;Zheng Yan
中科院分区：
文献类型：
--
作者：
Xi Chen;K. Burrell;T. Osborne;W. Solomon;K. Barada;A. Garofalo;R. Groebner;N. Luhmann;G. McKee;C. Muscatello;M. Ono;C. Petty;M. Porkolab;T. Rhodes;J. Rost;P. Snyder;G. Staebler;B. Tobias;Zheng Yan
在具有反应器相关边缘参数且无elm的DIII-D上发现了一个具有宽基座和改进的低旋转约束的静止、静态h模式（qh模式）。随着注入的中性梁扭矩逐渐减小，边缘E × B旋转剪切减小，发生了从标准QH到宽基座QH模式的过渡。在过渡阶段，通常调节标准QH边缘停止和宽带边缘MHD模式的相干边缘谐波振荡（EHO）随着基座压力高度（≥60%）和宽度（≥50%）的快速增加而出现。我们假设，由于低扭矩导致的下缘E × B流切变，增强的边缘湍流驱动输运降低了基座梯度，并结合平衡双零等离子体形状提供的高边缘不稳定性限制，允许发展更宽、更高的湍流输运限制基座。即使在基座压力显著提高的情况下，边缘工作点仍低于剥落气球模式稳定边界，因此没有elm。外核区域（0.8±0.9）输运的改善，由于该区域E × B流动剪切的增加和基座的增强，使整体约束提高了45%。这些发现为未来燃烧等离子体在低旋转条件下发展无elm的高约束运行奠定了物理基础。
A stationary, quiescent H-mode (QH-mode) regime with a wide pedestal and improved confinement at low rotation has been discovered on DIII-D with reactor relevant edge parameters and no ELMs. As the injected neutral beam torque is ramped down and the edge E × B rotation shear reduces, the transition from standard QH to the wide pedestal QH-mode occurs. At the transition, the coherent edge harmonic oscillations (EHO) that usually regulate the standard QH edge cease and broadband edge MHD modes appear along with a rapid increase in the pedestal pressure height (by ⩽60%) and width (by ⩽50%). We posit that the enhanced edge turbulence-driven transport, enabled by the lower edge E × B flow shear due to lower torque reduces the pedestal gradient and, combined with the high edge instability limit provided by the balanced double-null plasma shape, permits the development of a broader and thus higher pedestal that is turbulence-transport-limited. Even with the significantly enhanced pedestal pressure, the edge operating point is below the peeling ballooning mode stability boundary and thus without ELMs. Improved transport in the outer core region (0.8 ⩽ ρ ⩽0.9) owing to increased E × B flow shear in that region and the enhanced pedestal boost the overall confinement by up to 45%. These findings advance the physics basis for developing stationary ELM-free high-confinement operation at low rotation for future burning plasma where similar collisionality and rotation levels are expected.