Speaker
Description
The nonlinear stability characteristics and Alfvén instability driven transport are anticipated to have dominant effects in both tokamak and stellarator reactors. Based upon simulations with the 3D gyrofluid FAR3d model, we predict that EP populations will: drive significant levels of non classical EP transport; generate zonal flow shearing and zonal currents that impact thermal plasma microturbulence; and drive systemic intermittencies in the alpha heating and fusion power levels and EP particle losses that can decrease lifetimes of plasma-facing components. For these reasons, and the fact that EP populations in reactors exist in a multi-component, low $\rho_*$ regime (compared to current devices), a global multi-mode, multi-EP species model is required. Gyrofluid models provide an efficient, extensible platform for such studies. Two recent applications of this model to ITER and to optimized stellarator reactors will be described. For nonlinear simulations of ITER, energetic particle collective transport driven by phase relations between the fluctuating fast ion density and the fluctuating E x B and magnetic perturbations result in local profile flattening and zonal flow generation. This transport is nonlocal, with finite particle fluxes persisting in regions where the EP density gradients are zero. For stellarator reactors, the stabilizing effects of high-density operation have been assessed over a range of toroidal mode number families, resulting in burning plasma regimes with predicted very weak EP instability drive. Understanding and controlling alpha particle transport effects in burning plasma regimes in both tokamaks and stellarators is an important foundational element toward the success of these devices.
Acknowledgements - This research is sponsored by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under award: DE-AC05-00OR22725, and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.
| Presentation type | Oral |
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