ECCOMAS 2024

An electromagnetic model for SOLEDGE3X

  • Düll, Raffael (CEA-IRFM)
  • Bufferand, Hugo (CEA-IRFM)
  • Serre, Eric (AMU, CNRS, Centrale Marseille, M2P2)
  • Ciraolo, Guido (CEA-IRFM)
  • Quadri, Virginia (CEA-IRFM)
  • Rivals, Nicolas (CEA-IRFM)
  • Tamain, Patrick (CEA-IRFM)

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The SOLEDGE3X transport code, a collaborative development by CEA/IRFM and Aix-Marseille University, is a robust tool for simulating plasma turbulence in the tokamak edge region [1]. The primary driver of turbulent structures, the "ExB" drift, relies on an electrostatic assumption with a fixed equilibrium magnetic field. Recent studies suggest the significant role of electromagnetic effects in radial transport [2], filament shaping [3], and divertor heat fluxes [4]. Recent advancements [5] have incorporated an electromagnetic model into SOLEDGE3X, coupling the electric potential Φ with the parallel component of the electromagnetic vector potential A in one implicit system. The new field A is computed from the parallel current density J through Ampère's law. The introduction of a finite electron mass prevents unrealistic speeds but requires addressing the time evolution of J in the generalized Ohm's law. This term can be analytically included with minimal computational impact in the system with Φ and A, enhancing its numerical stability and smoothing the iterative solving process. Electromagnetic effects manifest in two forms: electromagnetic induction and flutter. The former results from temporal variations of A in Ohm's law, yielding basic electromagnetic behaviour in the form of shear Alfvén waves. On the other hand, electromagnetic flutter refers to perturbations of the equilibrium magnetic field caused by the local value of A. Simulations on a periodic slab case allow us to observe the predicted bifurcation of the wave propagation speed between the Alfvén wave and the electron thermal wave speeds for varying perpendicular wavenumbers. Initial results on a diverted geometry with an X-point configuration validate the feasibility of realistic turbulent electromagnetic scenarios. [1] Bufferand et al 2021 Nucl. Fusion 61 116052 [2] Furno et al 2008 Phys. Rev. Lett. 100, 055004 [3] Lee et al 2015 Journal of Nuclear Materials, 463, 765-768 [4] Xu et al 2019 Nucl. Fusion, vol. 59, 126039 [5] Düll et al expected 2024. submitted to: Contribution to Plasma Physics