Measurements of mosaicity and perfection of crystallites in commercially available crystals using a 4-axis perfect-crystal x-ray diffractometer.

Measurements of mosaicity and the intrinsic scattering from individual crystallites of commercially available crystals are presented. The set of crystals investigated has been proposed to be used as the energy dispersive element in a high resolution Bragg spectrometer for x-ray astronomy. The measurements reveal a high degree of perfection of the crystallites, even in the presence of considerable mosaicity. This is encouraging with relation to an eventual use of the crystals in a high resolution Bragg spectrometer for x-ray astronomy. The measurements were performed using a novel four-crystal x-ray diffractometer. The resolution properties of this diffractometer are discussed in detail and compared with more conventional three-crystal and twocrystal x-ray diffractometers.