Multiscale simulation of neutral particle flows in the plasma edge

Abstract: The plasma edge flow, situated at the intricate boundary between plasma and neutral particles, plays a pivotal role in the design of nuclear fusion devices such as divertors and pumps. Traditional numerical simulation methods, such as the direct simulation Monte Carlo approach and the discrete velocity method, are hindered by extensive computation times when dealing with near-continuum flow conditions. This paper presents a general synthetic iterative scheme to deterministically simulate the plasma edge flows. By alternately solving the kinetic equations and macroscopic synthetic equations, our method substantially decreases the number of iterations, while maintains asymptotic-preserving properties even when the spatial cell size is much larger than the mean free path. Consequently, our approach achieves rapid convergence and high accuracy in plasma edge flow simulations, particularly in near-continuum flow regimes. This advancement provides a robust and efficient computational tool, essential for the advancement of next-generation nuclear fusion reactors.