EMC3-EIRENE

EMC3-EIRENE is a state-of-the-art computational tool that combines the EMC3 (Edge Monte Carlo 3D) code with the EIRENE code to simulate plasma fluid and kinetic neutral edge transport in non-axisymmetric configurations. Developed for the study of stellarator and tokamak configurations, the code can model the full torus plasma and impurity transport, including the effects of 3D fields, such as resonant magnetic perturbations (RMPs). EMC3 is a 3D plasma fluid code that solves a set of reduced Braginskii fluid equations for particles, parallel momentum, and energies for electrons and ions. The code models parallel electron and ion heat conductivity using classical assumptions. Perpendicular transport is determined by coefficients for anomalous particle transport ($D_{\bot }$) and anomalous electron and ion heat transport ($\chi _{\bot }$), which are free model parameters. EIRENE is a kinetic edge transport code that solves the transport equations for neutral atoms and molecules, accounting for collisional processes. The code calculates ionization sources, momentum sources/losses, and energy sources/losses due to atomic/molecular processes, such as charge exchange and ionization. EMC3-EIRENE models impurity transport using a fluid approach, causing energy losses to the main plasma through excitation and ionization. The trace fluid approach assumes that impurities only cause small density perturbations and impacts the main plasma species through ionization and excitation via an energy loss term in the energy balance equation.

Several improvements have been made to the EMC3-EIRENE code to enhance its performance and capabilities:

• Implicit coupling to a 1D core model, eliminating ad hoc boundary conditions for intrinsic impurities at the SOL-core interface.
• Allowing non-uniform cross-field transport coefficients.
• Implementing a particle splitting technique to improve Monte Carlo statistics in low-temperature ranges.
• Enabling domain splitting in all three directions for mesh optimization in various divertor configurations.
• Relaxing stellarator-specific constraints on mesh construction.
• Moving axisymmetric neutral-facing components to cylindrical coordinates.

EMC3-EIRENE has been widely used to analyze 3D effects in stellarator and tokamak configurations. The code's ability to model plasma and neutral transport in inherently non-axisymmetric magnetic field configurations and its compatibility with various limiter designs make it a suitable tool for self-consistent 3D modeling of plasma and neutral transport in fusion devices.

The current version of EMC3-EIRENE does not include self-consistent treatment of magnetic or electric drift effects and volumetric recombination. Future developments may address these limitations and expand the code's capabilities.

References

• Y. Feng et al, Recent Improvements in the EMC3-Eirene Code, Contributions to Plasma Physics 54 (2014) 426-431
• T. Lunt et al, EMC3-Eirene simulations of particle- and energy fluxes to main chamber- and divertor plasma facing components in ASDEX Upgrade compared to experiments, Journal of Nuclear Materials 463 (2015) 744-747
• H. Frerichs et al, Synthetic plasma edge diagnostics for EMC3-EIRENE, highlighted for Wendelstein 7-X, Review of Scientific Instruments 87 (2016) 11D441
• A. Bader et al, Modeling of helium transport and exhaust in the LHD edge, Plasma Phys. Control. Fusion 58 (2016) 124006
• F. Effenberg et al, Investigation of 3D effects on heat fluxes in performance-optimized island divertor configurations at Wendelstein 7-X, Nuclear Materials and Energy 18 (2019) 262-267
• J.D. Lore et al, Measurement and modeling of magnetic configurations to mimic overload scenarios in the W7-X stellarator, Nucl. Fusion 59 (2019) 066041
• K. Schmid et al, Integrated modelling: Coupling of surface evolution and plasma-impurity transport, Nuclear Materials and Energy 25 (2020) 100821