Lorentz process with shrinking holes in a wall

We ascertain the diffusively scaled limit of a periodic Lorentz process in a strip with an almost reflecting wall at the origin. Here, almost reflecting means that the wall contains a small hole waning in time. The limiting process is a quasi-reflected Brownian motion, which is Markovian, but not strong Markovian. Local time results for the periodic Lorentz process, having independent interest, are also found and used. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.063/1.4717521]