Determination of the scattering cross section of calcium using the VESUVIO spectrometer

Abstract

With the aim to study the bound-atom neutron scattering cross section of natural calcium we measured the total cross sections of calcium carbonate and calcium oxide for the energy range between 10 −3 and 100 eV, at the VESUVIO spectrometer (Rutherford Appleton Laboratory, UK), where we carried out simultaneous transmission and Deep Inelastic Neutron Scattering measurements. We present a method that allows us to determine in situ the amount of water present in the samples, which are both of hygroscopic nature. By employing it, we were able to subtract the contribution of hydrogen from the total cross section, as well as that of the other atoms present in the sample whose amount was known by their stoichiometry, what allowed us to determine the calcium contribution. The process of quantifying the amount of water involves the analysis of the scattered neutrons and multiple scattering corrections. In order to perform this last correction, we made a prior study of the dynamics of the system by means of the Density Functional Theory technique, along with measurements of the vibrational spectra at the TOSCA spectrometer (Rutherford Appleton Laboratory, UK). The value determined for the bound-atom scattering cross section of calcium was 4.27 ± 0.04 barns.