大野 暢亮

Abstract At the National Institute for Fusion Science (NIFS), advanced visualization and analysis techniques using large-scale virtual reality (VR) systems and head-mounted displays (HMDs) are being developed to interpret various fusion plasma datasets. In particular, by projecting three-dimensional (3D) time-series trajectories of Li ion particle calculated for impurity powder dropper experiments in the Large Helical Device (LHD) into an immersive VR environment together with magnetic field line data, detailed analyses of Li ion transport phenomena have become possible. In deuterium plasma experiments in the LHD, trajectories of tritons generated by D-D fusion reactions and their collisions with plasma-facing components were computed. As a new visualization method, the collision points and the velocity vectors at the moments of impact were displayed in VR space. Visualizing the computed triton orbits in VR revealed collision events taking place behind the divertor plates, which had remained unnoticed using earlier analytical methods. In addition to these visualization capabilities, the present study provides a quantitative three-dimensional evaluation of particle transport and deposition. The analysis shows that Li ions generated from impurity powder injection are predominantly transported along open magnetic field lines in the peripheral plasma, with only limited penetration into closed flux surfaces. For energetic particles, the evaluation of prompt-loss triton impact density reveals that tritons are strongly localized on closed divertor plates, where the maximum impact density reaches approximately 0.08 m⁻², while smaller but finite fluxes are observed on first-wall components. These results highlight the critical role of three-dimensional magnetic topology and realistic device geometry in determining impurity transport and energetic particle deposition in helical fusion devices. In this context, immersive VR complements conventional visualization techniques by providing an interactive environment in which particle trajectories, magnetic field topology, collision points, velocity vectors, and realistic CAD geometry can be explored simultaneously, thereby facilitating the interpretation of complex 3D plasma transport and plasma–wall interactions. Although the physical conclusions are ultimately derived from the simulation data themselves, immersive VR provides a more effective environment for exploring and interpreting these data than conventional desktop-based visualization.