Abstract of ERO2-2 Project

ERO2.0 is an established code for modelling plasma-wall interaction and global material migration in fusion devices. The migration is simulated by following the 3D trajectories of Monte-Carlo test particles, which are representative of the eroded material, in the plasma edge. Acceleration by electromagnetic fields is taken into account, as well as atomic and molecular processes (ionisation, recombination, dissociation) and collisions (drift, diffusion). To obtain accurate trajectories in the sheath and impact velocities of the test particles, the 3D gyro-orbits are resolved (instead of applying the guiding-centre approximation).

Since large numbers (10⁶) of test particles are required to reduce Monte-Carlo noise, ERO2.0 is parallelised using a hybrid MPI/OpenMP scheme and routinely executed on the supercomputers like MARCONI-Fusion or JURECA. Due to the trace impurity approximation underlying the model, trajectories can be calculated independently of each other in parallel by individual OpenMP threads. Since trajectory lengths (proportional to the associated work load) can vary by orders of magnitude, a dynamic load-balancing algorithm is used. This minimises the idle run time of CPU cores, but requires extra communication between them.

In a previous HLST project in 2019, ERO2.0 was successfully ported to MARCONI-Fusion. Profiling tools were applied to identify potential performance issues and possible improvements. For the current project, we would like to build upon the obtained HLST experience and optimize ERO2.0. The aim of the optimizations is to prepare ERO2.0 for heavier simulations like for the DEMO reactor, which is larger than e.g. ITER and therefore requires more computing resources.