(a) Simulated image of the collimated beam. The integrated number of rays along each axis is indicated on the side panels. (b) Horizontal (red) and vertical (blue) simulated divergences of the collimated beam when χ = 90.011°; (green) vertical divergence of the collimated beam experimentally measured (intensities have been normalized). (c) Vertical divergences of the collimated beam along pathways S1S2 and S2S1 when χ = 90.115°. An additional divergence of about 87 µrad is introduced due to the shift between the two beams. The same gap is observed in the horizontal divergences (not shown).