Plasma dynamics in the tokamak edge

托卡马克边缘的等离子体动力学

• 批准号: 2889507
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2889507
• 关键词: Plasma; dynamics; tokamak; edge

Transport in the tokamak edge and scrape-off layer (SOL) plays a crucial role in determining the performance of a magnetic confinement fusion reactor. Turbulence in the edge likely sets the height of the pedestal that forms in high-confinement-mode discharges, and the associated transport sets the heat load to the vessel walls. Plasma dynamics in the edge and SOL are particularly challenging to model and to simulate due to, e.g., the presence of open field lines, neutral particles, extreme changes in magnetic geometry and large-amplitude fluctuations. As part of the ongoing ExCALIBUR/Neptune project, a group of researchers at Oxford - in collaboration with UKAEA colleagues - have created a novel, moment-based drift kinetic code to study the dynamics in the edge and SOL. The fundamental aim of the code is to solve efficiently a self-consistent version of the drift- and/or gyro-kinetic equation, while enabling a straightforward connection to fluid codes in the far SOL and delta-f gyrokinetic codes in the core. To our knowledge, all current codes are either prohibitively expensive for routine physics studies, use a simplified fluid treatment (possibly with a reduction in the number of dimensions considered) or use an inconsistent kinetic treatment. The moment-kinetic approach that we are pursuing should allow for a self-consistent kinetic treatment where required without undue numerical expense. At the moment the code solves only for either parallel dynamics (with or without the moment kinetic approach) or for a homogeneous, helical magnetic field (with only standard drift kinetics). Both versions of the code assume a simplified response for electrons that corresponds to a Boltzmann statistical equilibrium.Our proposal is for a PhD student based at Oxford to carry forward the code development; to continue with more advanced verification, validation and performance benchmarks; and to ultimately use the code to do fundamental physics studies. Key aspects of code development that could be explored include an extension to treat kinetic electrons, addition of collisions amongst charged particles, extension to 3D (non-helical) geometry, treatment of the separatrix region that ties together open and closed field line regions, addition of more sophisticated wall boundary conditions and a scheme for transitioning from drift kinetic to gyrokinetic or fluid models within a single simulation. There are a lot of avenues to explore, and which ones are addressed by the student will depend on the state of the code once the student gets up to speed, what will be seen as the most novel and timely contribution, which provides the most direct path to physics results and the relevance of the targeted physics to reactor design studies.This project falls within the EPSRC "Plasma and Lasers" and "UK Magnetic Fusion Research Programme" research areas.

托卡马克边缘和刮除层（SOL）中的输运在决定磁约束聚变反应堆的性能方面起着至关重要的作用。边缘的湍流可能决定了在高约束模式放电中形成的基座的高度，并且相关的传输决定了容器壁的热负荷。由于开放场线、中性粒子、磁几何形状的极端变化和大幅波动等因素的存在，边缘和 SOL 中的等离子体动力学建模和模拟特别具有挑战性。作为正在进行的 ExCALIBUR/Neptune 项目的一部分，牛津大学的一组研究人员与 UKAEA 同事合作，创建了一种新颖的基于力矩的漂移动力学代码来研究边缘和 SOL 的动力学。该代码的基本目标是有效求解漂移和/或陀螺运动方程的自洽版本，同时能够直接连接到核心中的远 SOL 中的流体代码和 delta-f 陀螺运动代码。据我们所知，所有当前的代码对于常规物理研究来说要么过于昂贵，要么使用简化的流体处理（可能会减少考虑的维数）或使用不一致的动力学处理。我们正在追求的矩动力学方法应该允许在需要时进行自洽的动力学处理，而无需过多的数值费用。目前，该代码仅求解并行动力学（有或没有矩动力学方法）或均匀螺旋磁场（仅具有标准漂移动力学）。两个版本的代码都假设电子的简化响应与玻尔兹曼统计平衡相对应。我们的建议是由牛津大学的一名博士生来推进代码开发；继续进行更高级的验证、确认和性能基准；并最终使用代码进行基础物理研究。可以探索的代码开发的关键方面包括处理运动电子的扩展、带电粒子之间碰撞的添加、3D（非螺旋）几何形状的扩展、将开放和闭合场线区域连接在一起的分界线区域的处理、附加更复杂的壁边界条件以及在单次模拟中从漂移动力学模型过渡到回旋动力学模型或流体模型的方案。有很多途径可以探索，学生解决哪些途径将取决于代码的状态，一旦学生加快速度，什么将被视为最新颖和最及时的贡献，这提供了最直接的贡献物理结果的路径以及目标物理与反应堆设计研究的相关性。该项目属于 EPSRC“等离子体和激光”和“英国磁聚变研究计划”的研究领域。