The frontier of magnetized plasma microturbulence lies in understanding the dynamics of multiscale driftwave turbulence in fusion reactor-relevant regimes. In a reactor, the plasma will be unstable to nonlinearly coupled instabilities at both the ion and electron gyroradius scales.
The research team proposes leveraging validation-quality datasets from reactor-relevant DIII-D H mode (high confinement) tokamak discharges, for which standard ion-scale simulations were unable to reproduce experimental electron heat fluxes, to begin a more rigorous validation of the multiscale gyrokinetic model and pushing into unexplored regimes. These studies will use multiscale gyrokinetic simulations with realistic ion-to-electron mass ratio, experimentally derived inputs, and electromagnetic effects to compare predicted transport in multiple channels directly against experiment. The results of this work will begin to shed light on whether cross-scale coupling will play an important role in reactor-relevant regimes, helping to define the requirements for reliable prediction of ITER and beyond.
To further investigate this issue, the team also proposes to attempt the first multiscale simulations of ITER plasmas. ITER is predicted (by state of-the-art reduced turbulence models) to have significant levels of electromagnetic, multiscale electron transport. They will assess the accuracy of these reduced model predictions against first-principles electromagnetic multiscale gyrokinetic simulation.
To investigate the importance of multiscale turbulence in reactor-relevant conditions, the team plans to utilize the newly developed gyrokinetic code, CGYRO. This successor to the well established code, GYRO, has been optimized for Titan and for performing multi scale simulations utilizing large numbers of ion species. The team seeks to take advantage of these optimizations to enable first-of-a-kind simulations of ITER and the first comparisons of multi scale predictions of thermal and particle transport to measurements from the DIII-D tokamak.
Ultimately, the completion of this work will begin to shed light on the multiscale nature of turbulence in ITER and the multiscale nature of particle transport in tokamaks, both of which must be accurately
predicted to realize the success of fusion as a viable commercial energy source.
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