This paper deals with the diffusion limit of a kinetic equation where thecollisions are modeled by a Lorentz type operator. The main aim is to construct adiscrete scheme to approximate this equation which gives for any value of theKnudsen number, and in particular at the diffusive limit, the right discretediffusion equation with the same value of the diffusion coefficient as in thecontinuous case. We are also naturally interested with a discretization whichcan be used with few velocity discretization points, in order to reduce the cost ofcomputation.
