Implementation of Ion Temperature Gradients withing the gyrofluid code FAR3D.

Recent experiments and simulations suggest the generation of shear flows during the saturation of Alfven Eigenmodes (AE) improves the thermal plasma confinement. This is explained by a reduction of the plasma turbulence linked to the stabilization of Ion Temperature Gradient (ITG) modes. The aim of this project is extending the gyro-fluid FAR3D code [1] to introduce ITG modes in the numerical model to study the connection between AEs and ITGs. These phenomena have been observed in tokamaks such as DIII-D and JET [2,3] and analyzed using gyrokinetic codes [4,5]. Given the numerical efficiency of the FAR3d code, the interaction between shear flows and ITG in the late saturate phase of the AEs can be explored, as well as providing a more general characterization of the phenomena by performing studies in a wider range of parameters. In this contribution we present the status of the project, which consist in the implementation of the ITG's in the linear version of FAR3d. First, the new and modified equations of the previous numerical model will be explained. Next, a showcase of simulations under the baseline of the LHD stellarator and the DIII-D tokamak will be shown. The implementation of the nonlinear model, currently in progress, is also discussed.

[1] J. Varela, et al, Front. Phys. 12:1422411 (2024).

[2] J. Garcia, et al, Nature communications, 15, 7846 (2024).

[3] W. Heidbrink, et al, APS DDP 2024, poster BP12.00012, October 7-11, Atlanta, USA (2024).

[4] Di Siena, et al "Understanding Turbulence Suppression in JET D-T Plasma with MeV Fast Ions via Global Gyrokinetic GENE Simulations", Nucl. Fusion, accepted.

[5] S. Mazzi, et al “Fast Ion Interaction with Turbulence in Tokamak Plasmas: Overview of the Recent Results”, Modern Plasma Physics journal, under review.