International Research Fellowship Program: Particle Tracking and Anomalous Statistics in a Basic Plasma Physics Experiment

0853498古斯塔夫森该奖项由2009年美国复苏和再投资法案(公法111-5)资助。国际研究奖学金计划使美国科学家和工程师能够在国外进行9至24个月的研究。该计划的奖项提供了联合研究的机会，并利用国外独特或互补的设施、专业知识和实验条件。该奖项将支持Kyle B.Gustafson博士与瑞士联邦理工学院的Paolo Ricci博士合作的为期24个月的研究奖学金。等离子体湍流在许多环境中都很重要，从聚变能源研究中的热和粒子传输到天体物理等离子体的加热。最近，用连续时间随机游动和分数扩散方程来描述输运的更精细的描述被应用于等离子体湍流的模拟。到目前为止，结果是令人振奋的，但与实际实验和观察的比较受到诊断可能性的限制。它还将对照实验的高分辨率数据验证和验证模拟，同时使用模拟来指导实验操作的重点。我们使用诊断方法，包括大型朗缪尔探针阵列、快速离子注入和带有快速相机的喷气成像。模拟基于三维流体方程，在生成场中进行被动粒子跟踪。我们解决了以下问题。粒子的能量、质量和电荷如何影响描述这些粒子输运的非布朗模型的相关性？器件的参数，如场拓扑、温度和密度的梯度，如何影响非布朗输运？计算结果和非布朗输运模型在多大程度上解释了不同条件下TORPEX的高分辨率数据，如何推广这些比较？洛桑的物理等离子体研究中心(CRPP)是聚变和工业等离子体物理研究的主要设施。被称为TORPEX的基本环形装置拥有一套完全独特的诊断方法，特别是用于研究颗粒在磁化湍流中的运动。TORPEX的模拟已经开发出来，并准备用于粒子跟踪研究。为此目的，CRPP的计算设施装备精良。这项研究与欧洲大规模和不断增长的等离子体物理努力相配合，包括具有里程碑意义的ITER实验。在天体物理学中，我们将更好地理解粒子的能量和加热。聚变能量的研究关键依赖于对粒子传输的适当表征，因为有效的机器必须在核心具有很大的能量密度。本研究将通过对TORPEX数据的分析和模拟来改进这一特征。

0853498GustafsonThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-four-month research fellowship by Dr. Kyle B. Gustafson to work with Dr. Paolo Ricci at Ecole Polytech Federale in Switzerland.Plasma turbulence is important in many contexts, from transport of heat and particles in fusion energy research to heating of astrophysical plasmas. An unresolved question of current interest is whether turbulent transport can generally be described using the standard diffusion equation derived from the assumptions of a Brownian random walk. Subtler descriptions of transport in terms of continuous time random walks and fractional diffusion equations have recently been applied to simulations of plasma turbulence. For example, continuous time random walks allow the distribution of step sizes and waiting times for the walkers to be non-Gaussian, possibly with power law dependence. Fractional diffusion equations describe the macroscopic propagation of an ensemble of particles using nonlocal, integro-differential operators in a generalization of the diffusion equation. The results so far have been promising, but comparison with actual experiment and observation has been limited by diagnostic possibilities. This International Research Postdoctoral Fellowship in Lausanne, Switzerland is intended to facilitate a search for anomalous, or non-Brownian, transport indications in a basic plasma experiment and, simultaneously, in simulations of the experiment. This approach will help confirm or deny the relevance of non-Brownian transport in a fundamental experiment, TORPEX, with an unprecedented set of diagnostic tools. It will also verify and validate simulations against highly resolved data from the experiment, while using the simulations to guide the focus of the experimental operation. We use diagnostics including a large Langmuir probe array, fast-ion injection and gas puff imaging with a fast camera. Simulations are based on three-dimensional fluid equations with passive particle tracking in the generated fields. We address the following questions. How do the energy, mass and charge of particles affect the relevance of non-Brownian models for describing transport of those particles? How do the parameters of the device, such as field topology and gradients of temperature and density, affect non-Brownian transport? To what extent do computational results and non-Brownian transport models explain the high-resolution data from TORPEX in various conditions and how can these comparisons be generalized?The Centre de Recherches en Physique des Plasmas (CRPP) in Lausanne is a major facility for fusion and industrial plasma physics research. The basic toroidal device called TORPEX possesses a completely unique set of diagnostics especially for studying the movement of particles in magnetized turbulence. Simulations of TORPEX have been developed and are ready to be used for particle tracking studies. The CRPP computational facilities are well-equipped for this purpose. This research synergizes with the large and growing plasma physics efforts in Europe, including the landmark ITER experiment. The results of these detailed experiments on plasma microturbulence will be shared with a variety of communities in the U.S. Results from the study of non-Brownian transport will be relevant to transport of turbulent heat and momentum and turbulent heating. In astrophysics, a better understanding of particle energization and heating will be achieved. Fusion energy research depends critically on a proper characterization of particle transport, since an effective machine must have a large energy density in the core. This characterization will be improved by the analysis of the data and simulations of TORPEX in this research.