In plasmahyphen;source ion implantation a target is pulse biased to a high negative voltage, forming an expanding plasma sheath. A numerical simulation model for the evolution of the sheath has been developed and compared successfully with experimental results. The model is one dimensional (planar, cylindrical, or spherical). The timehyphen;dependent, selfhyphen;consistent potential profile is calculated from Poissonrsquo;s equation coupled with collisionless fluid equations for the ions and a Boltzmann assumption for the electrons. In addition to the density and potential profile, the simulation yields the ion current to the surface and the energy spectrum of the ions hitting the surface.
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