Description
Accurate heat-load maps are needed to design tokamak divertor and first-wall (FW) components. Toroidal-field ripple and FW geometric features define heat fluxes on plasma-facing components (PFCs), while finite ion gyroradius effect enables particles to access shadowed regions such as divertor tile gaps and leading edges, producing local hot spots with high heat fluxes. State-of-the-art tools typically simulate either global ripple effects with field-line tracing or local gap physics with finite-gyroradius particle tracing, but applying finite-gyroradius methods to full-machine CAD models is computationally expensive.
In this work, a two-stage workflow is presented that combines a parallel 3D field-line tracer with the GYROHIT finite-gyroradius back-tracing solver [1]. In stage 1, magnetic field lines are traced in the full 3D magnetic field (including ripple effects) from the PFC surface to calculate an initial power-deposition map, resulting in the wetted area on a CAD-derived triangular mesh. The field-line stage uses adaptive Runge-Kutta integration and surface-intersection tests to process complex geometries. In stage 2, GYROHIT code is executed only on the wetted part of the geometry, where it samples gyro-orbits with realistic pitch and computes heat and particle fluxes with high spatial resolution.
By concentrating costly gyro-orbit sampling on the areas where particles from SOL regions arrive, the workflow increases resolution and accuracy of the heat flux mapping at diminished computational times. In this way, it allows multiple systematic runs over different magnetic configurations and edge-plasma parameters. The resulting heat-flux maps provide an insight into global 3D plasma loading distribution with detailed local hotspot, useful for PFC design verification.
[1] M. Radež et al., A novel approach to studying divertor gap heat loads, 20th International Conference on Plasma-Facing Materials and Components, Ljubljana 2025