Bandaru V, Hoelzl M, Artola F J, Papp G, Huijsmans G T A
Max Planck Institute for Plasma Physics, Boltzmannstaße 2, 85748 Garching, Germany.
ITER Organization, Saint Paul Lez Durance CS90046 13067, France.
Phys Rev E. 2019 Jun;99(6-1):063317. doi: 10.1103/PhysRevE.99.063317.
For the simulation of disruptions in tokamak fusion plasmas, a fluid model describing the evolution of relativistic runaway electrons and their interaction with the background plasma is presented. The overall aim of the model is to self-consistently describe the nonlinear coupled evolution of runaway electrons (REs) and plasma instabilities during disruptions. In this model, the runaway electrons are considered as a separate fluid species in which the initial seed is generated through the Dreicer source, which eventually grows by the avalanche mechanism (further relevant source mechanisms can easily be added). Advection of the runaway electrons is considered primarily along field lines, but also taking into account the E×B drift. The model is implemented in the nonlinear magnetohydrodynamic (MHD) code jorek based on Bezier finite elements, with current coupling to the thermal plasma. Benchmarking of the code with the one-dimensional runaway electron code go is done using an artificial thermal quench on a circular plasma. As a first demonstration, the code is applied to the problem of an axisymmetric cold vertical displacement event in an ITER plasma, revealing significantly different dynamics between cases computed with and without runaway electrons. Though it is not yet feasible to achieve fully realistic runaway electron velocities close to the speed of light in complete simulations of slowly evolving plasma instabilities, the code is demonstrated to be suitable to study various kinds of MHD-RE interactions in MHD-active and disruption relevant plasmas.
为了模拟托卡马克聚变等离子体中的破裂情况，提出了一种描述相对论性逃逸电子的演化及其与背景等离子体相互作用的流体模型。该模型的总体目标是自洽地描述破裂期间逃逸电子（REs）和等离子体不稳定性的非线性耦合演化。在这个模型中，逃逸电子被视为一种单独的流体种类，其中初始种子通过德赖塞尔源产生，最终通过雪崩机制增长（可以很容易地添加进一步的相关源机制）。逃逸电子的平流主要沿磁力线考虑，但也考虑了E×B漂移。该模型在基于贝塞尔有限元的非线性磁流体动力学（MHD）代码jorek中实现，电流与热等离子体耦合。使用圆形等离子体上的人工热猝灭，用一维逃逸电子代码go对该代码进行基准测试。作为第一个演示，该代码应用于ITER等离子体中轴对称冷垂直位移事件的问题，揭示了在有和没有逃逸电子的情况下计算的情况之间显著不同的动力学。尽管在缓慢演化的等离子体不稳定性的完整模拟中，实现接近光速的完全现实的逃逸电子速度尚不可行，但该代码被证明适用于研究MHD活跃和与破裂相关的等离子体中的各种MHD-RE相互作用。
