Abstract Details
Abstracts
Author: Arash Ashourvan
Requested Type: Consider for Invited
Submitted: 2024-03-29 14:18:15
Co-authors:
Contact Info:
General Atomics
3550 General Atomics Court
San Diego, CA 92121-1
United States
Abstract Text:
In the edge of an L-mode tokamak plasma, particle transport and ion energy transport are shown to follow a strong microturbulence (SMT) scaling, whereas in the plasma core the transport is shown to follow quasilinear turbulence (QLT) scaling. The dependence of diffusivity on potential fluctuation amplitude is linear in the quasilinear regime, and quadratic in the SMT regime. These distinct scaling regimes are determined from the direct calculation of Lagrangian diffusivity with a newly developed Lagrangian Gyrocenter Tracking code (LGT1). LGT1 launches and tracks test-particles into the time-varying saturated turbulence, which is pre-calculated by CGYRO. 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 and DE-FG02-95ER54309.
Comments:
1. Plasma equilibrium, stability, and transport
2. Physics of the plasma edge and divertor region, including plasma surface interactions
3. Analytic and computational methods for modeling plasmas