(a) Sketch of the diamond lenses, with the red arrows showing the approximate crystallographic directions. W, d and R correspond to the width, web size and radius at the parabola apex of the lens, respectively. All dimensions are in millimetres. (b) Scanning electron micrograph of the diamond plate with refractive lenses. (c) Impingement of the X-rays with the (1) center, (2) edge and (3) bulk material of the diamond lenses (from top to bottom). The notion of `bulk material' refers to the part with no profiling between CRL5 and CRL2.