发表机构
Lawrence Livermore National Laboratory; Columbia University in the City of New York（劳伦斯利弗莫尔国家实验室; 纽约市哥伦比亚大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
通过GDB全局湍流模拟，发现托卡马克边缘粒子箍缩由早期漂移波湍流和后期非理想E×B平衡通量两种机制驱动，自洽产生中心峰化密度分布，对密度台基形成有启示。
AI 中文摘要
在磁约束聚变实验中，向内粒子通量（即粒子箍缩）经常被观测到，但其机制尚未被完全理解。我们使用通量驱动的全局湍流模型GDB研究托卡马克边缘的粒子箍缩。从仅在最后闭合磁面附近加料的平坦密度分布出发，模拟发展出强烈的向内粒子通量，在约O(10)毫秒内建立起中心峰化的密度分布。该箍缩与通常的向外湍流热输运共存；两种不同的机制承载着它。在早期阶段，当密度和温度梯度相互对立时（η_α=L_n/L_{T_α}<0），漂移波湍流通过电子热扩散驱动向内通量。在后期阶段，一旦密度分布变平，由极向不对称密度和静电势携带的持续向内平衡E×B通量驱动中心峰化。虽然Pfirsch-Schlüter新经典输运设定了上下不对称密度的幅度，但经典理论预测该不对称性在领头阶不产生净径向通量。观测到的通量流经一个独立的非理想通道，该通道由平衡电子力平衡中的平行电阻率、电子惯性和电磁感应开启。该通道将平衡势相对于密度在极向上移动δ_s≈-0.08π，并供给后期密度增长。这些结果表明，通量驱动的全局边缘模拟可以在没有特设假设的情况下自洽地产生中心峰化的密度分布，并对密度台基形成等长期存在的边缘问题具有意义。
英文摘要
The inward particle flux, or particle pinch, is routinely observed in magnetically confined fusion experiments, yet its mechanism is not fully understood. We study the particle pinch in the tokamak edge with the flux-driven global turbulence model GDB. Starting from a flat density profile fueled only near the last closed flux surface, the simulation develops a strong inward particle flux that builds a centrally peaked density profile over $O(10)$ ms. The pinch coexists with the usual outward turbulent heat transport; two distinct mechanisms carry it. In the early stage, when density and temperature gradients oppose each other ($η_α=L_n/L_{T_α}<0$), drift-wave turbulence drives the inward flux through electron thermal diffusion. In the late stage, once the density profile has flattened, a persistent inward equilibrium $E\times B$ flux, carried by the poloidally asymmetric density and electrostatic potential, drives the central peaking. While the Pfirsch--Schlüter neoclassical transport sets the amplitude of the up-down asymmetric density, classical theory predicts no net radial flux from this asymmetry at leading order. The observed flux flows in a separate non-ideal channel, opened by parallel resistivity, electron inertia, and electromagnetic induction in the equilibrium electron force balance. This channel shifts the equilibrium potential poloidally against the density by $δ_s\simeq-0.08π$ and supplies the late-phase density build-up. These results show that a flux-driven global edge simulation can self-consistently produce a centrally peaked density profile without ad hoc assumptions, and bear on longstanding edge questions such as density pedestal formation.
Comments32 pages, 16 figures
