A diffraction grating, as could be used in a soft X-ray monochromator Blaze or trapezoidal angles, with the angle of the upstream facing edge listed first. Blazed gratings can be identified by the low value of the first-listed angle. List of polynomial coefficients describing the spatial separation of lines/grooves as a function of position along the grating, in increasing powers of position. Gratings which do not have variable line spacing will only have a single coefficient (constant). Angle between the incident beam and the utilised outgoing beam. An array describing the thickness of each layer A NXshape group describing the shape of the mirror Numerical description of the surface figure of the mirror. "Engineering" position of the grating