Abstract
A newly developed Lagrangian Gyrocenter Tracking code (LGT1) is used to analyze the turbulent transport by launching and tracking test-particles into the time-varying saturated turbulence, which is pre-calculated by the CGYRO Eulerian gyrokinetic code. In the edge of an L-mode tokamak plasma, particle transport and ion energy transport are shown to follow a strong microturbulence (SMT) scaling, which has a linear dependence of diffusivity on potential fluctuation amplitude [A. Ashourvan and J. Candy PRL 132, 205101 (2024)]. Conversely, in the plasma core, the transport is shown to follow quasilinear turbulence scaling, which has a quadratic dependence on potential amplitude. The transition to strong microturbulence results from larger E×B drift velocities in the edge compared to the plasma core. At these larger velocities, ions traverse the spatially correlated range faster than the stochastic evolution of the electric potential. Hence, these particles do not experience a time-stochastic field as required by the quasilinear approximation. Instead, scattering of particles in the SMT regime is caused by spatial stochasticity. In contrast, electron energy transport remains quasilinear due to decorrelations caused by collisions and fast parallel motion. Improved understanding of transport beyond quasilinear theory opens the path to more accurate modeling of transport in the tokamak plasma edge.
*This work was supported by US DOE under DE-FC02-06ER54873, DE-SC0024425 and DE-FG02-95ER54309.Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
