Speaker
Description
Heat exhaust remains a critical challenge for stellarator-based fusion reactors, from experimental machines like W7‑X to reactor candidates such as SQuID. Although significant progress has been made in tokamak divertor physics, including promising regimes such as detachment and X-point radiators (XPR), the extension of these solutions to the inherently three-dimensional stellarator geometry involve substantial challenges, both for the computational stellarator modelling and obtaining experimental detachment.
This contribution presents recent advances in terms of improvements to divertor and heat-exhaust modelling capabilities for quasi-isodynamic (QI) stellarators using the non-linear extended-MHD code JOREK, which only recently started being used to study detachment and similar phenomena. The primary technical challenge lies in implementing sheath boundary conditions (SBC) that accurately capture plasma-wall interactions in the complex non-axisymmetric 3D stellarator geometry. Unlike tokamaks, where 2D axisymmetric approximations are sufficient, stellarators require a full 3D treatment of the magnetic field structure and its intersection with divertor surfaces.
Our approach involves developing and validating a projection matrix that maps the fluid plasma onto the 3D divertor wall grid. To ensure code validation, we first benchmark against known tokamak solutions by simulating 2D axisymmetric cases within the 3D stellarator framework. Once validated, the 3D SBC implementation will be one of the key enablers of systematic studies of plasma detachment physics in stellarator divertors.
This work directly addresses power-exhaust requirements for future stellarator reactors and creates synergies with ongoing research on island divertors. By extending JOREK's proven capabilities to stellarator geometry, we aim to provide a validated tool for investigating detachment scenarios and radiative divertor solutions that are essential for stellarator-based power plants. Initial results from validation studies and preliminary 3D simulations will be presented, along with planned investigations of detachment physics in QI stellarator configurations.