On the resolution of neutron scattering instruments

Phase-space arguments are used to discuss the resolution of neutron scattering instruments. The usual practice in such studies is to assume that all beam elements have Gaussian profiles. Here, the assumption that all elements have rectangular profiles results in considerable clarification of the role of each instrument component. The discussion is limited to powder diffractometers and powder samples on three-axis spectrometers, but it is possible to use the results when considering more involved measurements. The choice of collimators and monochromator mosaic to optimize measurements is discussed. The assumption of rectangular elements is not entirely artificial, as it is now possible to build such components. Furthermore, the conclusions can be applied to instruments with Gaussian elements.