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Theoretical relations for optimum adjustments of two arrangements of a double‐bent‐crystal (DBC) small‐angle neutron scattering (SANS) diffractometer are discussed. Results of several experiments demonstrate the applicability of DBC SANS in the investigation of some technologically important materials in the range of scattering‐vector sizes 0.0002–0.02 Å−1. Formulas derived for data analysis, which describe the transformation of the SANS cross section to the measured intensity, indicate that water calibration is not required and that the indirect method of data evaluation is the most appropriate.

The optics of successive Bragg reflection by two bent crystals is considered in the lamellar approximation. The optimal curvatures ensuring minimal rockingcurve widths and good reflection efficiencies are determined. The conditions under which a rocking curve reproduces the reflectivity curve of a bent crystal are indicated. Analytical formulae for the rocking-curve width and peak intensity are derived for three simple limiting cases. The computations are supported by experimental results obtained with bent perfect silicon crystals.

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