Experimental and Computational Investigation of the Dynamics of Fluctuation Suppression by Controlled Flow Shear

本研究的目的是通过实验研究在受控的实验室环境中不稳定漂移波动状态（包括宽带湍流）和波动抑制状态之间转换的详细动力学。这些实验将通过与非线性流体湍流代码的直接比较来补充，该代码专门用于模拟本实验。拟议的实验将在新墨西哥大学（UNM）的双源HELCAT（螺旋阴极）装置中进行。HELCAT是一种灵活的设备，为这些实验提供了独特的重要功能。两个等离子体源-独立或同时操作-可以产生从单漂移模式到宽带漂移湍流的边缘波动等离子体。此外，等离子体偏置对Er × Bz流动剖面的影响已经得到证实，而在漂移波阻尼中很重要的碰撞作用已经发生了超过一个数量级的变化。阿拉斯加州费尔班克斯大学（University of Alaska Fairbanks）的合作者开发的数值代码是一个二维流体板静电波动模型，具有详细的诊断，以了解波动模式之间相互作用的动力学，将被修改以允许驱动器模拟实验驱动器。代码有一个外部流，可以打开它来查看流对波动模式的影响。该研究设施非常适合培养学生从事聚变能或研究等离子体中的湍流输运，这是一个在空间和天体物理等离子体以及磁约束实验室等离子体中重要的过程。这项研究可能对建立等离子体湍流传输预测模型的努力产生重大影响。本研究涉及基础等离子体物理、复杂动力学、空间等离子体和磁约束等离子体等领域。该提案已提交给NSF-DoE等离子体科学与工程合作项目联合招标08-589。该奖项由数学和物理科学理事会物理部资助。

The goal of this research is to investigate experimentally the detailed dynamics of transitions between states of unstable drift fluctuations (including broadband turbulence), and fluctuation-suppressed states in a controlled laboratory environment. These experiments will be complemented by direct comparisons with a nonlinear fluid turbulence code, adapted specifically to model this experiment. The proposed experiments will take place in the dual-source HELCAT (HELicon-CAThode) device at the University of New Mexico (UNM). HELCAT is a flexible device that provides unique capabilities important to these experiments. The two plasma sources- operated independently or simultaneously - can generate plasmas with edge fluctuations ranging from single drift modes to broadband drift turbulence. Additionally, plasma biasing to affect Er × Bz flow profiles has been demonstrated, and collisionality, important in drift wave damping, has been varied by more than an order of magnitude. The numerical code developed by the co-PI at the University of Alaska Fairbanks, a 2-D fluid slab model of electrostatic fluctuations with detailed diagnostics to understand the dynamics of the interaction between the fluctuating modes, will be modified to allow the drive to mimic the experimental drive. The code has an external flow that can be turned on to look at the impact of flow on the fluctuating modes.The research facility is well suited for training students for careers in fusion energy or studying turbulent transport in plasmas, a process important in space and astrophysical plasma as well as magnetically confined laboratory plasmas. The research could have a significant impact on efforts to create predictive models for turbulent transport in plasmas. This research is relevant to basic plasma physics, complex dynamics, space plasmas and magnetically confined plasmas.This proposal was submitted to the NSF-DoE Partnership in Plasma Science and Engineering joint solicitation 08-589. This award is being funded by the Division of Physics of the Mathematical and Physical Sciences Directorate.