Neutron absorption correction and mean path length calculations for multiple samples with arbitrary shapes: application to highly absorbing samples on the Multi-Axis Crystal Spectrometer at NIST

Recent advancements in cold neutron instrumentation, designed to achieve the energy resolution necessary for studying strongly correlated materials, have driven the need for sophisticated modeling of neutron spectroscopy data from highly neutron-absorbing materials. These absorption effects are often highly dependent on both angular orientation and wavelength. To address this, the finite-volume algorithm for absorption correction developed by Wuensch & Prewitt [ Z. Kristallogr. (1965), 122 , 24–59] is examined in this paper in the context of cold neutron spectroscopy. This algorithm is based on the numerical integration of the transmission function, where three-dimensional quadratic surfaces define the sample boundaries. The algorithm can also determine the mean path length required for second-extinction calculations. We apply this method to neutron inelastic scattering measurements of an irregularly shaped CeRhIn 5 single crystal using the Multi-Axis Crystal Spectrometer at NIST. The algorithm has been expanded to correct for the absorption of multiple coaligned samples. We show that this procedure can account for the angle-dependent absorption, and the technique can be used to correct the data and plan experiments.