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Gyrokinetic simulations of turbulence are fundamental to understanding and predicting particle and energy loss in magnetic fusion devices. Previous works have used model collision operators with approximate field-particle terms of unknown accuracy and/or have neglected collisional finite Larmor radius effects. This research moves beyond models to demonstrate important corrections using a gyrokinetic Fokker-Planck collision operator with the exact field-particle terms, in realistic simulations of turbulence in magnetically confined fusion plasmas. The exact operator shows significant corrections for temperature-gradient-driven trapped electron mode turbulence and zonal flow damping, and for microtearing modes in a Joint European Torus pedestal under ITER-like wall conditions.more » Analysis of the corrections using parameter scans motivates an accurate model which closely reproduces the exact results while reducing computational demands.« less

Edge plasmas present a few challenges for gyrokinetic simulations that are absent in tokamak cores. Among them are large fluctuation amplitudes and plasma-wall interactions in the open field line region. In this work, the widely used core turbulence code GENE, which employs a δf-splitting technique, is extended to simulate open systems with large electrostatic fluctuations. With inclusion and proper discretization of the parallel nonlinear term, it becomes equivalent to a full-f code and the δf-splitting causes no fundamental difficulty in handling large fluctuations. The loss of particles to the wall is accounted for by using a logical sheath boundary, whichmore » is implemented in the context of a finite-volume method. The extended GENE code is benchmarked for the well-established one-dimensional parallel transport problem in the scrape-off layer during edge-localized modes. The parallel heat flux deposited onto the divertor target is compared with previous simulation results and shows good agreement.« less