Development of Advanced Linearized Gyrokinetic Collision Operators Using a Moment Approach

Abstract

The derivation and numerical implementation of a linearized version of the gyrokinetic (GK) Coulomb collision operator (Jorge R. et al., J. Plasma Phys. 85, 905850604 (2019)) and of the widely-used linearized GK Sugama collision operator (Sugama H. et al., Phys. Plasmas 16, 112503 (2009)) is reported. An approach based on a Hermite-Laguerre moment expansion of the perturbed gyrocenter distribution function is used, referred to as gyro-moment expansion. This approach allows considering arbitrary perpendicular wavenumber and expressing the two linearized GK operators as a linear combination of gyro-moments where the expansion coefficients are given by closed analytical expressions that depend on the perpendicular wavenumber and on the temperature and mass ratios of the colliding species. The drift-kinetic (DK) limits of the GK linearized Coulomb and Sugama operators are also obtained. Comparisons between the gyro-moment approach with the GK continuum code GENE are reported focusing on the ion-temperature-gradient (ITG) instability and zonal flow (ZF) damping, finding an excellent agreement. In particular, we demonstrate that the GK linearized Sugama yields a stronger collisional damping of the ZF residual compared to the GK linearized Coulomb. Finally, we show that the numerical efficiency of the gyro-moment approach increases with collisionality, a desired property for boundary plasma applications.

published version

References in corpus (5)

• Linearized model Fokker-Planck collision operators for gyrokinetic simulations. I. Theory
• Global turbulence simulations of the tokamak edge region with GRILLIX
• Local and global Fokker-Planck neoclassical calculations showing flow and bootstrap current modification in a pedestal
• New velocity-space discretization for continuum kinetic calculations and Fokker-Planck collisions
• Conservative discontinuous Galerkin scheme of a gyro-averaged Dougherty collision operator

Cited by in corpus (6)

• Improved multispecies Dougherty collisions
• Local Gyrokinetic Collisional Theory of the Ion-Temperature Gradient Mode
• Gyrokinetic simulations of plasma turbulence in a Z-pinch using a moment based approach and advanced collision operators
• Full-F Turbulent Simulation in a Linear Device using a Gyro-Moment Approach
• Numerical Implementation of the Improved Sugama Collision Operator Using a Moment Approach
• Metriplectic foundations of gyrokinetic Vlasov-Maxwell-Landau theory