Determination of effective temperatures through affordable concurrent techniques in CANS

Abstract

Experimental techniques involving epithermal neutrons can be used to study the kinetic energies of the atoms that make up the sample material. From the point of view of Nuclear Engineering, this is the range of energies that is necessarily traversed in the moderation process. From the point of view of applied physics, it is an essential range for the design of neutron sources associated with compact accelerators. It is also worth mentioning that experimental access to this energy range is a distinctive feature of accelerator-based sources as opposed to reactor-based sources. The atoms that compose the matter perform motions characterised by a kinetic energy, determined not only by the temperature of the medium, but also by interactions resulting in vibrational modes. We can thus define a parameter that we call effective temperature, linked to this effect. The knowledge of the densities of the vibrational states allows its evaluation, so that spectroscopic techniques aimed at its measurement allow an indirect assessment of it. Yet, there are techniques that allow direct experimental access to these quantities which are Deep Inelastic Neutron Scattering (DINS) and Neutron Transmission (NT). The VESUVIO spectrometer (ISIS, UK) allows both techniques to be performed simultaneously in the same experiment. Although ISIS is a large neutron source, such experiments were previously carried out at the defunct LINAC in Bariloche (Argentina), making these techniques affordable for small sources. In this work we show this capability through combined DINS and transmission experiments in a molecular liquid. We also discuss different prospects for future use, extending the possibilities to other techniques.