Varied Groove Depth Gratings (VGD) The gratings of the CASSIOPEE beamline are quite special. They focus the beam thanks to their varied line spacing (VLS). The groove depth also varies along the direction perpendicular to the beam. Hence, by choosing the position of the grating with respect to the beam, one can choose the groove depth experienced by the beam to optimize the grating reflectivity at each photon energy. They were made by the Jobin-Yvon company (Lonjumeau, France).
