The XeCl laser facility Hercules, delivering a maximum energy of 8 J in 160 ns FWHM, has been used to irradiate amorphous silicon (a-Si) films on glass substrate. We designed an optical homogeneizer to reshape the large cross-section of the laser beam (10×5) cm2, in order to reach a fluence up to 0.5 J/cm2 over a (13×1) cm2 area. The beam resulted spatially homogenous within 10% (referred to peak-to-peak fluctuations). We obtained poly-silicon films with grain size ranging from 0.1 to 2 μm, depending on the laser energy density. These preliminary results show that the grain size is critically fluence-dependent when the so-called super-lateral-growth regime is approached (approximately at 0.42 J/cm2 for a 50 nm-thick a-Si film), with a maximum slope of the grain size vs. energy density greater than 0.5 μm/(mJ/cm2).