Second-order neutron optics of three-axis spectrometers. I. Quasielastic scattering

The basics of second-order neutron optics for bent-crystal three-axis spectrometers are presented. Energy-transfer resolution for quasielastic scattering is examined in detail. Experimental data illustrating the effect of second-order aberrations are presented. The resolution of energy transfer at 5 meV neutron energy with bent monochromators made from commercial thin silicon wafers was improved to 8 µeV from a previous record of 16 µeV.