The crystalline quality of these diamond plates was qualitatively evaluated by synchrotron X-ray RC measurement and topography as described next. At the 1-km beamline of SPring-8 (BL29XUL) [13], the topographs were acquired under quasi-plane wave incidence using a Si collimator [14]. Table 1 shows the experimental conditions (reflection plane, collimator, photon energy). A CCD-based X-ray camera with a pixel size of 12 μm was used to capture the topographs. The topographs were acquired at the peak and low-angle side tail region of the RC. The RCs were measured with footprints over the entire surface of the crystals and in a narrow area (250 × 250 μm) selected by a slit.