Numerical modeling of Li, Sn and W sputtering and redeposition in plasma sheaths with oblique magnetic fields

Understanding impurity redeposition in plasma–wall transition regions is essential for predicting the lifetime and performance of plasma-facing components in fusion devices. In this work, the sheath-driven redeposition of sputtered lithium, tin, and tungsten is investigated using a Monte Carlo code coupled to electrostatic potential profiles obtained from Particle-in-Cell simulations. The study examines the influence of magnetic field inclination to the wall, plasma conditions, ionization processes, and incoming ion species on redeposition dynamics. In the context of an academic study, the sheath electric field is suppressed, and three redeposition regimes are identified depending on the relative magnitudes of the ionization mean free path, plasma–wall transition extent, and impurity gyroradii. A theoretical expression for long-range redeposition is derived and shown to accurately reproduce simulation results when gyromotion effects remain weak. The inclusion of self-consistent sheath electric fields significantly enhances redeposition and reduces its dependence on magnetic inclination. Heavy impurities such as Sn and W exhibit high redeposition fractions in compact-like scenarios because their shorter ionization mean free paths lead to ionization in regions of strong electric field, whereas Li is more easily ionized outside the sheath region. The influence of projectile mass and charge state is also analyzed through binary collision theory. These results highlight the dominant role of sheath electric fields and ionization physics in determining impurity redeposition near plasma-facing surfaces.