A comprehensive molecular dynamics study of deuterium trapping and bubble formation on tungsten

Understanding the trapping and de-trapping mechanisms of hydrogen isotopes on plasma facing materials (PFMs) of fusion devices is critical due to concerns of safety, fuel economy, and device efficiency. Recent computational and experimental studies focusing on deuterium bombardment on tungsten, current candidate of PFMs of tokamak design fusion reactors, show that nano-sized bubbles are formed in subsurface region of tungsten due to high concentration of deuterium. In this study, the deuterium bombardment with various energies on tungsten structures including monocrystalline and polycrystalline with grain boundary at various temperatures was simulated by molecular dynamics methods employing Large-scale Atomic/Molecular Parallel Simulator (LAMMPS) code. The Tersoff interatomic potential is employed to determine interaction between particles. The parameters of deuterium trapping such as trapping rate, implantation depth, and the mechanism of bubble formation are analyzed. Additionally, the D bubble formation is observed during high temperature (600K or higher) tungsten simulations. The bubble formation is being analyzed to study the effect of other parameters, e.g., crystalline structure, deuterium energy, etc. The goal is to identify reasonable operating windows for candidate PFMs to enhance lifetime.