Optimization of the bent perfect Si(3Â 1Â 1)-crystal monochromator for a residual strain/stress instrument at the HANARO reactor-Part I

Reflectivity and resolution properties of a variety of optimized focusing monochromator performances based on cylindrically bent perfect Si-crystals were tested with the aim of evaluating their possible use in a strain/stress diffractometer. It has been found that the optimized monochromator performances of the curved Si(3 1 1) crystals (for the take-off angle 2θM=60°) provide a good luminosity and a sufficiently high resolution (full width at half maximum (FWHM) of the instrumental Δd/d-profile can be about 2×10−3 in the vicinity of the lattice spacing d=0.117nm for 2θS≈90°) of the strain/stress diffractometer with the figure of merit more than one order of magnitude larger than that related to the conventional flat mosaic Ge(2 2 0) monochromator of η=15′.