ORB5X is the modern C++17 refactoring of ORB5: a global, electromagnetic, multi-species gyrokinetic code for studying turbulence, energetic-particle physics, Alfvén eigenmodes, and transport in toroidal magnetically confined plasmas. It uses a low-noise \(\delta f\) particle-in-cell (PIC) method for the distribution functions and a finite-element representation of the fields.

The C++ implementation retains the physical model and numerical organization of the adjacent Fortran sources while replacing architecture-specific kernels with Kokkos execution and memory spaces. MPI decomposes the simulation across processes; Kokkos provides performance portability across multicore CPUs and supported GPU backends.