Speaker
Description
One the greatest uncertainties in the success of magnetically confinement fusion is related to turbulent transport in the boundary region of fusion devices, which controls the heat flux to the wall and the access to high confinement regimes. Because of the wide range of spatial and time scales that characterize turbulence in magnetic confinement plasma devices and the complex magnetic geometries, a deep understanding of turbulent transport in this region can only be attained by combining highly-resolved measurements with the results of complex three-dimensional turbulence simulations.
RFX-mod (Consorzio RFX, Padua, Italy) is a flexible machine that can operate both as high-confinement (H-mode) tokamak and as high-current Reversed Field Pinch (RFP). This unique feature allows for a direct comparison of boundary turbulence in the two very different magnetic configurations. The RFX-mod turbulence simulations presented here are carried out with the state-of-the-art GBS code [1].
The first part of the talk is devoted to turbulence simulations of a RFX-mod diverted plasma in the presence of a biasing electrode, which has been recently implemented in GBS. The simulations show a strong suppression of turbulent transport caused by the flow shear generated by the biasing electrode, leading to the formation of an edge transport barrier with a pedestal-like structure, which agrees qualitatively and quantitatively with RFX-mod experiments [2].
The results of pioneering global flux-driven turbulence simulations in RFP plasmas are presented and discussed in the second part of the talk. These simulations are performed considering (i) a self-organized magnetic field that features multiple magnetic islands and significant magnetic chaos, and (ii) a simplified magnetic field where only the dominant magnetohydrodynamics modes are retained. A comparison between these two cases reveals a relatively weak effect of magnetic chaos on turbulence, while the electrostatic radial electric field is found to be deeply influenced by stochastic transport.
References
[1] M. Giacomin et al. J. Comput. Phys. 463 (2022) 111294.
[2] M. Giacomin et al. Nucl. Fusion 65 (2025) 036013.
This work has been funded by the European Union - NextGenerationEU (“NEFERTARI – New Equipment for Fusion Experimental Research and Technological Advancements with Rfx Infrastructure”). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. We acknowledge EuroHPC JU for awarding the project ID EHPC-REG-2024R02-031 access to Discoverer HPC (Sofia Tech Park, Bulgaria) and CINECA (Italy) for awarding access to Leonardo HPC under the ISCRA initiative (project ID IscrB_GBSRFP).