Turbulence in the edge of tokamaks

托卡马克边缘的湍流

基本信息

批准号：
EP/G049718/1
负责人：
Felix Parra Diaz
金额：
$ 32.4万
依托单位：
University of Oxford
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FG049718%2F1
关键词：
Turbulence edge tokamaks

项目摘要

Nuclear fusion is a clean, inexhaustible source of energy. It only requires specific isotopes of hydrogen and it does not emit carbon dioxide or leave nuclear waste. It is a complex technology because fusion reactions require extremely high temperatures and, under such conditions, the hydrogen gas is ionised. Fusion energy is then faced with the challenge of confining ionised gas (known as plasma) of high energy density. However, the prize at hand is so attractive (and more so now in an increasingly energy-conscious world) that the fusion community is involved in a worldwide effort to develop a viable fusion reactor. As a result, ITER is being built in Cadarache (France) and several other experiments (JET, in UK, among the most important) are currently working intensively on different aspects of the problem. This international collaboration can only be compared to the previous experience in particle accelerators.The concept behind ITER and JET is magnetic confinement (the plasma is held in equilibrium by magnetic fields). Magnetic confinement has proven the most effective fusion method so far and, among all possibilities, the tokamak is the most successful (ITER and JET are tokamaks). A tokamak is an axisymmetric toroidal configuration with a dominant toroidal magnetic field and a smaller poloidal magnetic field. Tokamaks were proposed in Russia in the 1950s, and since then they have been subject to extensive research. Even so, there is still a crucial area where our knowledge is incomplete, namely, turbulent transport of energy and particles to the walls of the vessel. Understanding the processes that lead to the observed energy and particle losses, and controlling them, are necessary steps prior to the construction of a successful fusion energy plant. Over the last ten years, there has been a notable effort directed at unravelling the physics of turbulent transport in tokamaks. As a result, we have learnt that the energy stored in the tokamak mainly depends on the temperature at the edge of the plasma.In tokamaks, in what is known as a high confinement mode or H-mode, the temperature at the edge of the plasma is determined by a transport barrier that sits just at the edge of the plasma. The physics in this transport barrier, known as the pedestal, determines the difference in density and temperature between the hot core and the cold, partially ionised edge. Unfortunately, the pedestal is still poorly understood. My research programme focuses on the physics of the pedestal, in particular, on how phenomena specifically relevant to the plasma edge affects turbulence. Most turbulence research has been aimed at the plasma core, where the plasma is fully ionised, the walls of the vessel are far away and the defects of the magnetic field geometry are small. In the pedestal, however, these features matter. To study them, I am developing analytical models that will be useful to gain physical insight and to construct meaningful benchmarks for more complex works (several groups around the world are intensively working on large numerical simulations). Most of my research is on the effect of defects in the magnetic geometry on the level of saturation of the turbulence. Magnetic geometry is an important ingredient in the torodial velocity evolution, and toroidal velocity shear decorrelates the turbulence, controlling the level at which the turbulence reaches its equilibrium. I attempt to understand this relationship using both linear and nonlinear analyses.

核融合是一种干净，无尽的能源。它仅需要特定的氢同位素，并且不发射二氧化碳或留下核废料。这是一项复杂的技术，因为融合反应需要极高的温度，并且在这种情况下，氢气被电离。然后，融合能面临限制高能密度的离子气体（称为等离子体）的挑战。但是，手头的奖项是如此吸引人（现在在一个日益激烈的世界中），以至于融合社区参与了全球开发可行的融合反应堆的努力。结果，ITER是在Cadarache（法国）和其他几个实验（在英国最重要的一项）中建造的，目前正在大力研究问题的不同方面。这种国际合作只能与粒子加速器的先前经验进行比较。iTer和JET是磁性限制的概念（等离子体在磁场平衡中保持平衡）。迄今为止，磁性限制已被证明是最有效的融合方法，在所有可能性中，Tokamak是最成功的（Iter和Jet是Tokamaks）。 Tokamak是带有主要环形磁场和较小的磁场磁场的轴对称环形构型。 1950年代在俄罗斯提出了Tokamaks，从那时起，他们就进行了广泛的研究。即便如此，仍然存在一个关键领域，我们的知识是不完整的，即能量和颗粒向容器壁的湍流运输。了解导致观察到的能量和颗粒损失的过程，以及控制它们是在建造成功的融合能量厂之前的必要步骤。在过去的十年中，旨在揭开Tokamaks动荡运输物理的显着努力。结果，我们了解到，托卡马克中存储的能量主要取决于等离子体边缘的温度。在托卡马克斯（Tokamaks）中，在所谓的高约束模式或H模式下，血浆边缘的温度由位于血浆边缘的传输屏障确定。该传输屏障（称为基座）中的物理学决定了热芯与冷，部分电离边缘之间的密度和温度差异。不幸的是，基座仍然很熟悉。我的研究计划侧重于基座的物理学，特别是现象与等离子体边缘的影响如何影响湍流。大多数湍流研究都针对等离子体核心，该等离子体核心完全离子，容器的壁距离很远，并且磁场几何形状的缺陷很小。但是，在基座中，这些特征很重要。为了研究它们，我正在开发分析模型，这些模型将有助于获得物理洞察力并为更复杂的作品构建有意义的基准（世界各地的几个小组都在进行大型数值模拟）。我的大部分研究都是关于磁性几何形状缺陷对湍流饱和水平的影响。磁性几何形状是摩托式速度演变中的重要成分，环形速度剪切剪切使湍流解变，控制湍流达到其平衡的水平。我尝试使用线性和非线性分析来理解这种关系。