线性磁化等离子体装置中平均流、带状流与湍流的相互作用

The plasma turbulence and its related anomalous transport have attracted much attention for many years. Recently researchers are glad to find that there have some self-regulated mechanisms in plasma turbulence, for instance, the Reynolds Stress driven shear flow and the ZF-DW system.Generated by the nonlinear energy transfer from drift wave turbulence (DW), ZFs in magnetically confined plasmas contribute no cross field transport due to their azimuthal symmetry. Therefore the formation of ZFs will naturally reduce the level of trans- port caused by DW. The transport is further suppressed by the shearing effect of ZF on DW, as the back reaction of ZF to DW. Thus ZFs and DW constitute a self regulated energy conservation system, which is commonly referred to as DW-ZF turbulence. The related research about the ZF-DW system will provide possible future method to improve the plasma confinement in the coming ITER era. In this project, we will seek in linear plasma device for the possible experimental evidence of the co-existence of Zonal flow and shear flow, both driven by the ambient plasma turbulence. Also we will investigate the generation and saturation mechanisms for these flows, so that we know better about the self-modulated dynamics of the complex plasma system with mean flow, zonal flow and turbulence.

等离子体湍流及其引起的反常输运一直是等离子体物理学界的重要难题之一。近二十年来，人们幸运地发现湍流本身提供了可能的自调节机制，如湍流雷诺协强驱动的极向流、调制不稳定性产生的带状流等，这些机制为等离子体约束性能的进一步改善提供了可能的手段。极向流、带状流均可从湍流背景中提取能量，而且极向流剪切及带状流对湍流的剪切可以抑制湍流所驱动的输运。平均极向流-带状流-湍流共同组成一个自调节的非线性动力学系统，它们之间的相互耦合决定了湍流的饱和幅度和输运水平。因此对这一系统自调节行为的理论、模拟和实验研究已成为磁约束等离子体研究中的重要的前沿课题。本项目的研究目标是给出在线性磁化等离子体中存在低频带状流以及湍流驱动的极向流共存的实验证据，探索平均流-带状流-湍流的自调节动力学行为，并研究这些流的产生和饱和机制。

本项目针对国内外实验研究现状和存在的问题，着重提出利用线性磁化装置上等离子体可近性好，诊断完备等特点，系统研究等离子体中平均流-带状流-湍流这一复杂非线性系统的自调节动力学机制。项目执行期间，所开展的主要研究内容与结果有：发展氧化物阴极等离子体放电技术，实现了等离子体参数的宽泛调节；发展了若干新的参数诊断工具，如利用离子声波测量离子温度，激光诱导荧光测量流速及离子温度等；发现了快速判断低频带状流存在的在线实验鉴别方法，大幅度提高了实验效率；首次明确给出了低频带状流在时域的表现形式；并通过多涨落场时序信号系统对比给出了带状流产生及其对湍流剪切作用的物理图像；给出了低频带状流对湍流输运抑制的具体作用途径，主要是带状流随机剪切导致极向电场及密度涨落的去相关；研究了平均剪切流对等离子体状态的影响；开展了系列相关的数值模拟及理论研究。