Kinetic analysis of ion incident angle distribution on a plasma-facing wall

A one-dimensional particle simulation model of a magnetic presheath was presented and a simulation study was made to reveal the effect of the magnetic field on the ion incident angle distribution on a plasma-facing surface of a fusion device. Two kinds of plasma source due to the cross-field diffusion in the scrape-off layer and the ionization in the collisional presheath are considered to model the velocity distribution function at the entrance of the magnetic presheath. The dependence of the ion incident angle distribution was examined and a fitting form of the energy flux to the surface was obtained as a function of the incident angle and the magnetic field. A transition of the incident angle distribution was found. Dependences of the incident angle on the magnetic field strength vanishes when the magnetic field becomes weaker or stronger than threshold values. In the transition, when the magnetic field approaches parallel to the surface, incident angles become large.