Verification and Validation of Integrated Simulation of Energetic Particles in Toroidal Plasmas

Gyrokinetic simulations of energetic particles (EP) interactions with thermal plasmas focus on the DIII-D discharge #159243, which is a NBI-heated plasma with many small-amplitude reversed shear Alfven eigenmodes (RSAE) and toroidal Alfven eigenmodes (TAE), significant flattening of the EP profile, and large amplitude microturbulence. GTC linear simulations using EFIT equilibrium and experimental profiles find that the most unstable AE is RSAE with significant growth rate for toroidal mode number n=3-6. The most unstable RSAE is n=4 and has a radial domain of ⍴=0.3 - 0.6 (square-root of normalized toroidal flux function). These results are in good agreement with other gyrokinetic and gyrokinetic MHD-hybrid codes, as well as experimental data. Consistent with experimental observation, GTC simulations also find that weaker TAE exists at the outer radial domain of ⍴=0.6 - 0.9. Finally, GTC simulations find strong driftwave instability excited by thermal plasma pressure gradients in the core. The linear ITG-like mode amplitude peak at ⍴=0.3, but large fluctuations nonlinearly spread to the whole radial domain. These results indicate that RSAE and TAE in this DIII-D experiment could interact nonlinear with each other and with the microturbulence.