Author: Lee F Ricketson
Requested Type: Consider for Invited
Submitted: 2022-03-04 13:02:33
Co-authors: L. Chacón, G. Chen, O. Koshkarov
Lawrence Livermore National Laboratory
7000 East Ave
The gyrokinetic approximation has been tremendously successful in modeling fusion plasmas, but is not without obstacles – boundary conditions for gyrokinetic equations are difficult to formulate, and there is increasing interest in applications where the approximation may break down in portions of the domain. One is thus motivated to return to full-orbit kinetic simulation, while retaining the ability to step over the fast gyration time-scale when justifiable. With this in mind, we present several improvements to our previously reported asymptotic-preserving time integrator for implicit particle-in-cell (PIC) schemes. While retaining the scheme’s desirable properties – energy conservation, capturing of all first-order drift motions – we extend it to also accurately reproduce finite Larmor radius effects even when stepping over the gyration time-scale. We also report on an efficient Picard iteration that allows the implicit solve of particle motion for very large timestpes to converge quickly and robustly, as well as proof-of-principle simulations in self-consistent electrostatic PIC simulations of uniformly magnetized plasmas, where we see great computational gains.
*Prepared by LLNL under Contract DE-AC52-07NA27344.