GYROKINETIC SIMULATION OF ENERGETIC PARTICLE TURBULENCE AND TRANSPORT

The confinement of energetic particles (EP) is a critical issue for burning plasma experiments such as ITER, which will rely on the self-heating by energetic fusion products (a-particles) to sustain ignition. The fusion SciDAC GSEP Center (Gyrokinetic Simulation of Energetic Particle Turbulence and Transport) has successfully established gyrokinetic turbulence simulation as a necessary paradigm shift for studying the energetic particle confinement in burning plasmas. In this GSEP 1-year renewal we will perform new collaborative research on:

1. Validation of critical gradient model for time-averaged EP transport by using DIII-D EP experiments and large scale nonlinear simulations, and prediction of self-consistent EP profiles in DIII-D and ITER experiments; and

2. Dynamics of transient behaviors of EP turbulence by using large scale nonlinear simulations, and validation of nonlinear gyrokinetic simulations for DIII-D chirping modes.

The time-averaged EP transport measures the overall EP confinement level required to sustain ignition in ITER. Meanwhile, severe damage to the ITER wall could be caused by the high peak to average transient behaviors of EP turbulence such as the bursting characteristics of chirping modes and avalanche phenomena. This research would bridge the gap in modeling capability and nonlinear validation for predicting both time-averaged EP profiles and transient behaviors of EP turbulence. The validation and prediction requires nonlinear gyrokinetic simulation covering multiple spatial-temporal scales and incorporating multiple physical processes (e.g., EP instability, microturbulence, and MHD modes). The proposed research therefore represents a significant step in the validation of the first-principles, integrated simulation toward building predictive capability for long pulse, burning plasmas.