A non-twisting flux tube for local gyrokinetic simulations

Abstract Local gyrokinetic simulations use a field-aligned domain that twists due to the magnetic shear of background equilibrium. However, if is strong and/or long, twist can become so extreme it fails properly resolve turbulence. In this work, we derive and implement ‘non-twisting flux tube,’ local simulation remains rectangular at all parallel locations. Convergence runtime tests indicate calculate heat more efficiently than conventional tube. For one test case, was 30 times less computationally expensive found no case for which expensive. It most advantageous when high includes least two regions turbulent drive (e.g. stellarator simulations, pedestal tokamak with several poloidal turns). Additionally, accurately models inboard midplane large. Lastly, show how non-twisting tube be generalized allow further optimization control domain.