Speaker
Description
Substantial progress towards fusion reactors is expected in the coming years for both tokamaks and stellarators. Achieving this progress requires accurate predictions of plasma evolution. Integrated modelling frameworks such as JINTRAC and TOPICS enable detailed, time-dependent multi-physics simulations but typically involve long computation times. Fenix complements such suites as a 'flight simulator' by reaching run times of only a few minutes using computationally efficient reduced models. It combines the FEQIS equilibrium solver with the ASTRA transport solver to compute plasma equilibrium and transport, and it incorporates a simulated control system built on the Plasma Control System Simulation Platform (PCSSP) framework, enabling end-to-end scenario simulations with self-consistent plasma–control interaction.
Currently, however, ASTRA and FEQIS are limited to tokamak geometries, as parts of ASTRA’s transport model assume axisymmetry. Although stellarator-specific solvers such as NTSS exist, a unified transport solver applicable to both tokamaks and stellarators is still lacking. Developing such a solver would facilitate direct comparisons between device concepts and support a unified flight-simulator framework.
Here, we report recent extensions of the 1D transport code ASTRA that make it suitable for modelling plasma evolution in tokamaks as well as stellarators. Central to this effort is the derivation and implementation of a generic current diffusion equation formulated for the poloidal magnetic flux. In addition, ASTRA is coupled to the 3D equilibrium code VMEC, allowing the transport evolution to be advanced consistently with stellarator equilibria and enabling self-consistent updates of key magnetic-geometry quantities. The upgraded model is benchmarked against theoretical expectations and further compared with experimental observations from Wendelstein 7-X, evolving the bootstrap current and electrical conductivity self-consistently. The simulation reproduces the measured time evolution of the toroidal current with good accuracy. These developments turn ASTRA into a unified transport tool that supports transport studies and scenario comparisons across multiple magnetic-confinement approaches.