The JOREK non-linear extended MHD code and applications to large-scale instabilities and their control in magnetically confined fusion plasmas

JOREK is a massively parallel fully implicit non-linear extended magneto-hydrodynamic (MHD) code for realistic tokamak X-point plasmas. It has become a widely used versatile simulation code for studying large-scale plasma instabilities and their control and is continuously developed in an international community with strong involvements in the European fusion research programme and ITER organization. This article gives a comprehensive overview of the physics models implemented, numerical methods applied for solving the equations and physics studies performed with the code. A dedicated section highlights some of the verification work done for the code. A hierarchy of different physics models is available including a free boundary and resistive wall extension and hybrid kinetic-fluid models. The code allows for flux-surface aligned iso-parametric finite element grids in single and double X-point plasmas which can be extended to the true physical walls and uses a robust fully implicit time stepping. Particular focus is laid on plasma edge and scrape-off layer (SOL) physics as well as disruption related phenomena. Among the key results obtained with JOREK regarding plasma edge and SOL, are deep insights into the dynamics of edge localized modes (ELMs), ELM cycles, and ELM control by resonant magnetic perturbations, pellet injection, as well as by vertical magnetic kicks. Also ELM free regimes, detachment physics, the generation and transport of impurities during an ELM, and electrostatic turbulence in the pedestal region are investigated. Regarding disruptions, the focus is on the dynamics of the thermal quench (TQ) and current quench triggered by massive gas injection and shattered pellet injection, runaway electron (RE) dynamics as well as the RE interaction with MHD modes, and vertical displacement events. Also the seeding and suppression of tearing modes (TMs), the dynamics of naturally occurring TQs triggered by locked modes, and radiative collapses are being studied.Peer ReviewedPostprint (published version

Serendipity Shape Function for Hybrid Fluid/Kinetic-PIC Simulations

The Sun in our solar system and stars are capable of generating enormous amounts of energy. The process by which these gaseous, celestial bodies are able to produce such large amounts of energy is called thermonuclear fusion. Fusion happens when particles collide with one another at energy levels high enough to overcome the Coulomb force and then release vast amounts of energy. Plasma, the fourth state of matter, is the natural state of stars. Plasma is an ionized gas that consists of negatively and positively charged particles. Stars, which have immense mass, can confine the plasma through their gravity to sustain the fusion process. Laboratory plasma cannot be confined by gravity. Magnetic fields can be used instead. For the past 70 years, scientists and engineers have been working on harnessing energy from magnetized thermonuclear fusion. Current research contributes to creating a device capable of supporting fusion reactions and producing a clean sustainable energy source. Sustaining a burning or ignited plasma through fusion reactions is not an easy task. These complex systems can result in many instabilities that limit plasma temperatures and densities and prevent significant thermonuclear fusion from taking place. An important piece of the physics puzzle that either stabilizes or destabilizes the plasma is the interaction of energetic particles with the bulk plasma. This is called the wave-particle interaction or energetic particle interaction with magnetohydrodynamic (MHD) modes. Another example of this would be the solar wind from the sun (energetic particles) interacting with Earth’s magnetosphere (bulk plasma). This thesis focuses on an approach to more accurately and efficiently resolve the energetic particle motions using a computer code. This thesis will also compare two very different approaches to wave-plasma interaction problem by looking at the grow-rate of an instability that has been used to benchmark several computer codes used by the magnetic fusion energy community