Hamiltonian model for simplified island divertor grids and magnetic field chaos studies

We present HaGrids, a Hamiltonian model developed to generate computational grids and analyze magnetic field chaos in island divertor configurations. In real space, the configuration represents island chains formed on top of circular flux surfaces. This model is employed to construct field-aligned grids for EMC3-EIRENE simulations by generating a 2D base mesh and performing field-line tracing. Initial simulations compare cases with and without magnetic field chaos. In the chaotic case, strong secondary perturbations create extended chaotic regions at the edge, enabling efficient heat transport from the confined plasma through the chaotic zone to the divertor targets. This leads to flattened radial profiles across the chaotic region and a noticeable reduction in core confinement. In the case studied here, the formation of secondary strike lines, due to turnstile-lobe dynamics, broadens the target heat deposition and reduces the peak heat flux by ∼20%; the precise reduction depends on the perturbation spectrum, target geometry, and transport coefficients. The flexibility of the model allows for the exploration of a wide range of perturbation spectra and target geometries, offering a powerful tool for divertor studies and optimization beyond fixed-coil configurations.