  Dynamical focusing of ensembles of neutral particles in energy and
configuration space has been demonstrated recently [C. Petri et al. 2010, Phys.
Rev. E (R) {\bf 82}, 035204] using time-dependent elliptical billiards. The
interplay of nonlinearity, dissipation and driving yields the occurrence of
attractors in the phase space of the billiard. Here we show that dissipative
oval billiards with slowly oscillating elliptical scatterers in the interior
allow for a dynamical focusing on simple periodic trajectories with close to
perfect efficiency. This setup should be more amenable to corresponding
experiments which are briefly discussed.
