Speaker
Description
A few years ago, the nonlinear extended MHD code JOREK [2] has been extended with a dedicated kinetic neutral model [3], opening up the possibility to transiently model the interplay between edge-plasma and plasma-wall interactions and the plasma processes for which JOREK is well known such as ELMs, disruptions and RE beams, where previously these worlds could not be self-consistently combined in any code. Since then, the kinetic neutral model has been further developed and used as exhaust code by a growing part of the JOREK community and has attracted increasingly more attention from the exhaust physics field.
The MHD model in JOREK uses a flux surface aligned poloidal finite element grid up to the true first wall with the option to model variation in the toroidal direction using Fourier expansion. The kinetic neutral model is built on JOREK’s hybrid OMP-MPI particle-in-cell framework [4] and follows an array of variable weight particles through time, accumulating sources and sinks that are fed into the plasma equations. Both the MHD side and the kinetic side are inherently suited and optimized for time dependent modelling, making the model interesting for investigating dynamic physics and for control. Included in the neutral model physics are ionisation, charge exchange, wall – and volume recombination, line radiation and puffing, while molecular interactions are currently still missing.
As part of recent developments, various kinetic applications in JOREK (neutrals, impurities, runaway electrons and fast particles) have been combined into a single flexible kinetic framework, with object oriented control of the simulation setup, such that the included particle species, the particle pushers used for each species and the kinetic-MHD coupling scheme can be selected. Additionally, the neutral model is now compatible with a two temperature plasma description; direct binary neutral self-collisions have been added; and capability to resolve simulation actions (such as neutral collisions) on timescales in between the MHD timestep and
the kinetic particle timestep have been implemented. Furthermore, there is work underway for GPU acceleration and making the kinetic neutral model compatible with stellarator geometry.
This talk will discuss JOREK’s kinetic neutral model, how it is implemented and what is and is not currently included in the physics, along with details on the recent upgrades, encountered issues, and a selection of application and validation simulations of small ELM burn-through, XPR formation and transition into a MARFE, QCE access, and dynamic detachment studies.
[1] Hoelzl, Nucl. Fusion 66 (2026) 116006.
[2] Hoelzl, Nucl. Fusion 61 (2021) 065001.
[3] Korving, Phys. Plasmas 30 (2023) 042509.
[4] van Vugt, PhD Thesis, TU Eindhoven, 978-90-386-4811-8 (2019).