A γ-ray diffractometer: a tool for investigating mosaic structure

A single-crystal diffractometer has been constructed for use with γ-radiation of wavelengths down to λ = 0.03 Å. The relative line width at room temperature of the 412 keV line of radioactive gold is Δλ/λ = 10⁻⁶. The angular divergence of the primary beam in the scattering plane is equal to 10′′. The wavelength is so short that the Bragg scattering in imperfect single crystals with an effective thickness of 1 mm or more can be made extinction-free. Therefore the measured rocking curves represent mosaic distribution functions well and normally no deconvolution problems are involved in the interpretation of these curves. Because the absorption of the 412 keV γ-radiation is small (the mean free path for example being about 11 mm for copper), measurements with targets contained in ovens, cryostats, or high-pressure devices can be easily performed.