ORB5: a global electromagnetic gyrokinetic code using the PIC approach in toroidal geometry

• Published in: arXiv.org 2019-05
• Main Authors: Lanti, E, Ohana, N, Tronko, N, Hayward-Schneider, T, Bottino, A, McMillan, B F, Mishchenko, A, Scheinberg, A, Biancalani, A, Angelino, P, Brunner, S, Dominski, J, Donnel, P, Gheller, C, Hatzky, R, Jocksch, A, Jolliet, S, Lu, Z X, Martin Collar, J P, Novikau, I, Sonnendrücker, E, Vernay, T, Villard, L
• Format: Article
• Language: English
• Subjects: Adiabatic flow; Computer simulation; Drift; Electrons; Heat sources; Mathematical models; Noise control; Noise reduction; Zonal flow (meteorology)
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1905.01906

This paper presents the current state of the global gyrokinetic code ORB5 as an update of the previous reference [Jolliet et al., Comp. Phys. Commun. 177 409 (2007)]. The ORB5 code solves the electromagnetic Vlasov-Maxwell system of equations using a PIC scheme and also includes collisions and strong flows. The code assumes multiple gyrokinetic ion species at all wavelengths for the polarization density and drift-kinetic electrons. Variants of the physical model can be selected for electrons such as assuming an adiabatic response or a ``hybrid'' model in which passing electrons are assumed adiabatic and trapped electrons are drift-kinetic. A Fourier filter as well as various control variates and noise reduction techniques enable simulations with good signal-to-noise ratios at a limited numerical cost. They are completed with different momentum and zonal flow-conserving heat sources allowing for temperature-gradient and flux-driven simulations. The code, which runs on both CPUs and GPUs, is well benchmarked against other similar codes and analytical predictions, and shows good scalability up to thousands of nodes.