Verification/validation and physics model extension in high fidelity 3D RF full wave simulations on Petra-M

This paper reports the recent progress towards a whole-device scale RF actuator simulation. Our approach is to combine progresses made by open source scientific and math software communities for meshing, FEM assembly, and linear solvers to construct an integrated FEM fullwave simulation framework (the Petra-M FEM framework). The goal is to bring in engineering CAD level geometrical detail to our wave simulation capability, and advanced RF wave physics models, such as RF rectified sheath models and non-local hot plasma effects. In Petra-M, the high harmonic fast wave (HHFW) propagation was fully resolved in a 3D NSTX-U torus. In the NSTX-U simulation, the ratio between wavelength to the device size reaches 15, which is in the range required for resolving the ICRF wave fields in ITER. Verification and validation of the RF wave field computed by Petra-M through the international/multi-institutional efforts has been a major research focus, which yields an excellent code benchmark agreement between Petra-M, TOPICA and RAPLCIASOL. The spectral analysis of 3D wave field has been performed to interrogate the wave field behavior, which shows the consistency with the wave theory. RF rectified potential model was incorporated in our wave field solver. We developed a new non-linear iteration algorithm, which allows for using both the thick sheath (asymptotic) model and non-linear sheath impedance models seamlessly. The 3D RF sheath simulation on the WEST ICRF antenna indicates that the sheath potential tends to concentrate near the corner of antenna box, which is consistent with experimental observation of RF induced heat load pattern.