Recent diamond single crystal x-ray optics developments at the European Synchrotron Radiation Facility

In an effort to provide synchrotron x-ray beamlines with improved monochromators, a new series of 111-oriented diamond crystals up to 50 mm(2) large with thicknesses ranging from 67 mu m to 175 mu m was prepared, tested and found to be of very high quality. One sample appeared to be without any defects. Some linear defects were observed by topography on the other samples but without any consequences for the rocking curve width, except for one sample that revealed some mosaicity in part of its volume and could serve as variable flux/resolution monochromator. The rocking curve width exceeded sometimes the theoretical perfect crystal value by a couple of arcsec. Peak and integrated reflectivities were observed to be very dose to the theoretical values for a perfect diamond crystal. For the first time, a diamond crystal was elastically bent to achieve sagittal focusing. Although the bending was not absolutely uniform, a spot size of 21 mu m and gain factors exceeding one order of magnitude were obtained. These results showed that dispersion-free diamond double crystal monochromators of the classical type can be made.