Increase of turbulence and transport with resonant magnetic perturbations in ELM-suppressed plasmas on DIII-D
Increase of turbulence and transport with resonant magnetic perturbations in ELM-suppressed plasmas on DIII-D
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DOI：
10.1088/0029-5515/53/11/113011
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发表时间：
2013-11
期刊：
影响因子：
3.3
通讯作者：
G. Mckee;Z. Yan;C. Holland;R. Buttery;T. Evans;R. Moyer;S. Mordijck;R. Nazikian;T. Rhodes;O. Schmitz;M. Wade
中科院分区：
文献类型：
--
作者：
G. Mckee;Z. Yan;C. Holland;R. Buttery;T. Evans;R. Moyer;S. Mordijck;R. Nazikian;T. Rhodes;O. Schmitz;M. Wade
应用共振磁场扰动（RMPs）抑制边缘局域模式（elm），可以显著增加DIII-D等离子体外部区域的长波湍流。相应地，在这些低碰撞RMP-ELM抑制放电中，输运增加，整体能量约束减少。核心和基座密度急剧下降，而离子和电子温度可能只有轻微的变化。用波束发射光谱测量的60-300 kHz范围内的低波数密度湍流（k⊥ρi < 1）是修正的，并且通常在等离子体的整个外部区域（0.6 < ρ < 1.0）随着rmp在q95值范围内的响应而增加；相反，在q95中，ELM抑制发生在较窄的范围内。径向磁场调制实验表明，这些湍流变化发生在ρ = 0.85-0.95附近的几毫秒或更短的时间尺度上，明显快于输运时间尺度，也快于这些位置的局部压力梯度和剪切速率的演变。当内部线圈电流以方波方式从3.2 kA调制到4.2 kA时，湍流幅度在相位上变化了30%或更多，而局部密度仅变化了百分之几。这种动力学行为表明，湍流直接受到RMP的影响，这可能部分或很大程度上解释了由此导致的基座运输增加和稳定，防止被认为是驱动elm的剥落气球不稳定性。
Long-wavelength turbulence increases dramatically in the outer regions of DIII-D plasmas with the application of resonant magnetic field perturbations (RMPs) that suppress edge-localized modes (ELMs). Correspondingly, transport increases and global energy confinement decreases in these low-collisionality RMP-ELM suppressed discharges. The core and pedestal density are sharply reduced, while ion and electron temperatures may change only slightly. Low wavenumber density turbulence (k⊥ρi < 1) in the range of 60–300 kHz, measured with beam emission spectroscopy, is modified and generally increases throughout the outer region (0.6 < ρ < 1.0) of the plasma in response to RMPs over a range of q95 values; ELM suppression, in contrast, occurs for a narrower range in q95. Radial magnetic field modulation experiments indicate that these turbulence modifications occur on a time scale of a few milliseconds or less near ρ = 0.85–0.95, significantly faster than transport time-scales and faster than the local pressure gradients and shearing rates evolve at these locations. As the internal coil current is modulated in a square-wave fashion from 3.2 to 4.2 kA, the turbulence magnitude varies in phase by 30% or more, while local density changes by only a few per cent. This dynamical behaviour suggests that the turbulence is directly affected by the RMP, which may partially or largely explain the resulting increased transport and stabilization of the pedestal against peeling–ballooning instabilities that are thought to drive ELMs.