Validated scattering kernels for triphenylmethane at cryogenic temperatures

Florencia Cantargi,José Ignacio Márquez Damian,Goran Skoro,Javier Dawidowski,Julio Gabriel Cuello,Giovanni Romanelli,Matthew Krzystyniak,Christian Helman,Rolando Jose Granada

doi:10.1051/epjconf/202023914002

Abstract

Cold neutrons are widely used in different fields of research such as the study of the structure and dynamics of solids and liquids, the investigation of magnetic materials, biological systems, polymer science, and a rapidly growing area of industrial applications. In a pulsed neutron source where the pulse width is an important parameter to be considered, hydrogenated materials are often used because of their high energy transfer in each collision. The preliminary scattering kernel for triphenylmethane, a material of great potential interest for cold neutron production, had been presented at the ND2016 conference. Here, a new model for the generation of the scattering kernels for this material, together with experimental results on its total cross section measured at the VESUVIO instrument (ISIS Neutron and Muon Source, United Kingdom) is presented. The thermal scattering kernel was generated by means of the NJOY Nuclear Data Processing system, using as input the vibrational modes obtained by density functional theory techniques (DFT). The agreement between measurements and our model validates the scattering kernel construction and the cross section library generated in ENDF and ACE formats.

Highlights

The development and optimization of advanced cold neutron sources requires neutronic calculations involving thermal and sub-thermal neutron energies, which in turn demand the knowledge of reliable cross section data relative to the materials which form the system under consideration
In the frame of the Gaussian approximation the dynamics of the material is enclosed in its generalized frequency spectrum ρ, and this is the important piece of information we need to predict scattering probabilities in the case of hydrogenous materials, where interference effects are negligible
The main goal of this work is the generation of a thermal cross section library for triphenylmethane at a low temperature, and its validation with experimental data obtained at the VESUVIO instrument (ISIS Neutron and Muon Source, Rutherford Appleton Laboratory)

Summary

Introduction

The development and optimization of advanced cold neutron sources requires neutronic calculations involving thermal and sub-thermal neutron energies, which in turn demand the knowledge of reliable cross section data relative to the materials which form the system under consideration. In the frame of the Gaussian approximation the dynamics of the material is enclosed in its generalized frequency spectrum ρ, and this is the important piece of information we need to predict scattering probabilities in the case of hydrogenous materials, where interference effects are negligible. Another group of potential moderator materials is being studied. Thiphenylmethane (C19H16) had been proposed as a potentially good cold moderator due to its high protonic density and good radiation resistance [3] This molecular compound is formed by three phenyl groups connected through a central carbon atom, being a colorless solid at room temperature. The main goal of this work is the generation of a thermal cross section library for triphenylmethane at a low temperature, and its validation with experimental data obtained at the VESUVIO instrument (ISIS Neutron and Muon Source, Rutherford Appleton Laboratory)

Thermal scattering law libraries generation

Experimental results on triphenylmethane cross-section

Conclusions