The temporal evolution of the plasma sheath during plasma source ion implantation(PSII) is crucial because it affects the resultant surface properties and structures. In this paper two dimensional fluid model is applied to the problem in computing ion dynamics in the sheath of the end of a cylindrical bore using an auxiliary electrode for finite rise time voltage pulses. The ion density, flux, dose distributions are calculated by solving Poisson's equation and the equations of ion motion and continuity using finite difference methods. Our results indicate that there exist the differences of ion flux and dose among the inner, outer surfaces and the end surface of the bore.