Extended drift-kinetic full-f turbulent simulation of a linear plasma device using the gyro-moment approach

Turbulent full-f simulations in a linear plasma device are presented. Extending the work of Frei et al (2024 Phys. Plasmas 31 012301), the simulations are based on a drift-kinetic (DK) model that includes corrections associated with higher-order drifts and finite Larmor radius (FLR) effects, while avoiding the Boussinesq approximation. To solve the DK equation, the ion distribution function is expanded on a Hermite-Laguerre basis and the expansion coefficients, denoted as the gyro-moments (GMs), are evolved. Convergence is demonstrated with a small number of GMs and the ion distribution function is shown to be, approximately, a bi-Maxwellian distribution. The simulations reveal significantly reduced cross-field transport with respect to standard DK simulations. Turbulent structures are observed, predominantly elongated in the parallel direction, and largely unaffected by the number of GMs. Linear investigations of the unstable turbulent modes reveal the presence of a long-wavelength Kelvin-Helmholtz mode and a short-wavelength mode driven unstable by finite FLR corrections. The role of these modes in the nonlinear simulations is discussed.