Abstract
The turbulence and transport expected in the SPARC tokamak Primary Reference Discharge (PRD) [P. Rodriguez-Fernandez et al., J. Plasma Phys. 86, 865860503 (2020)] have been investigated with the gyrokinetic code CGYRO [J. Candy et al., J. Comput. Phys. 324, 73–93 (2016)]. Linear and nonlinear simulations that focus on ion (kθρs<1.0) and electron-scale (kθρs>1.0) turbulence were used to probe the nature of the turbulence and the resulting transport in the fusion core. It is found that in the SPARC PRD, ion temperature gradient (ITG) turbulence is expected to dominate transport over most of the profile with some potential trapped electron mode impact in the near edge. Stiff turbulence is observed over a part of the plasma core such that SPARC's ion temperature profile will likely be pinned to just above the critical gradient for ITG. The role of electromagnetic turbulence, rotation, and electron-scale turbulence was investigated to provide some insight into the physics required to accurately predict SPARC performance via gyrokinetics. Additionally, predictions of impurity peaking for potential low- and high-Z SPARC first-wall materials are probed using ion-scale simulation. The dominance of low-k turbulence in SPARC provides a potential opportunity for more tractable prediction of plasma profiles using nonlinear gyrokinetics. This work is the first step toward full gyrokinetic profile prediction of SPARC kinetic profiles and the resulting fusion power and plasma gain.
Highlights
The world fusion program is poised to enter a new era
In order to probe the nature of the turbulence and transport in SPARC and provide some insight into the accuracy of the 1.5D modeling, we present the analysis of linear and nonlinear gyrokinetic simulations for the SPARC Primary Reference Discharge (PRD) using the CGYRO code.[13,14]
Scitation.org/journal/php not predict the performance of SPARC directly, as self-consistent profile prediction using gyrokinetics will require extreme computational resources. It represents an investigation of SPARC conditions with gyrokinetics and helps to answer two questions: (1) Does the turbulence and transport in SPARC look similar or dissimilar to current day fusion devices and (2) What physics needs to be captured by gyrokinetic simulation to enable accurate prediction of plasma profiles and performance
Summary
The world fusion program is poised to enter a new era. With ITER on the horizon and a host of new fusion experiments proposed to reach burning plasma conditions, there is an increased need to apply our most advanced computational models to predict device performance and even influence their design and operation. In order to probe the nature of the turbulence and transport in SPARC and provide some insight into the accuracy of the 1.5D modeling, we present the analysis of linear and nonlinear gyrokinetic simulations for the SPARC PRD using the CGYRO code.[13,14] This work builds off of recent results by utilizing the kinetic profiles obtained from TRANSP modeling[11] as the starting point for the gyrokinetic analysis Scitation.org/journal/php not predict the performance of SPARC directly, as self-consistent profile prediction using gyrokinetics will require extreme computational resources Instead, it represents an investigation of SPARC conditions with gyrokinetics and helps to answer two questions: (1) Does the turbulence and transport in SPARC look similar or dissimilar to current day fusion devices and (2) What physics needs to be captured by gyrokinetic simulation to enable accurate prediction of plasma profiles and performance.
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