Molecular Dynamics Simulations in Plasma-wave-material Interaction for Nuclear Fusion Study

In a fusion plasma device, the high-temperature plasma must be confined in a vacuum vessel, where the plasma is designed to contact the divertor plate to minimize vessel depletion. We used molecular dynamics (MD) to study the damage to the divertor plates caused by plasma irradiation. Here, the plasma-matter interaction (PMI) is calculated by MD for elementary processes. Recently, starting from this PMI study, we have extended the range of its application beyond the divertor plate: MD allows us to obtain the trajectory of the motion of a lot of of particles by numerical integration of the classical equations of motion. We took advantage of this feature to quantitatively evaluate the effect of tritium on biomolecules (DNA). Tritium is the fuel of fusion reactors and a radioactive isotope of hydrogen. Only the internal exposure when tritium is taken into the body needs to be controlled. For fusion power generation to be accepted by society, it is necessary to accumulate scientific knowledge so that the risk of tritium can be rigorously evaluated. Therefore, DNA damage caused by tritium was evaluated using MD. The third topic is the electromagnetic (EM) field often used in the heating of fusion plasmas. We consider optical vortices, which are EM beams with orbital angular momentum. It is known that when a metal is irradiated by an optical vortex, the surface of the material becomes a helical nanostructure, which we have succeeded in creating on the computer using MD. As mentioned above, we introduce three examples of MD research used in fusion research.