SearcharxivSearch

arXiv subjects

J. R. Granada

Publications and source records attributed to J. R. Granada.

3 recordsLinked to original sources

Critique on the measurement of neutron cross-sections by the Deep Inelastic Neutron Scattering technique

We analyze a recent work of Mayers and Abdul-Redah,[J.Phys.: Condens. Matter {\bf 16}, 4811 (2004)] in which the autors report the existence of anomalous neutron cross sections in several systems. In the present work we show that the Deep Inelastic Neutron Scattering (DINS) results presented by the authors are affected by an inaccurate formalism employed for obtaining nuclear momentum distributions, and therefore definitive conclusions cannot be drawn on the subject of anomalous cross sections. We also show the reasons why the exact formalism for obtaining momentum distributions that we recently published must be employed for analysing the experimental data instead of the approximations performed in the mentioned work. We also point out serious inconsistencies between different results reported in the mentioned work, as well as incompatibilities with previous results published by the authors. These inconsistencies, as well as experimental evidence against the existence of anomalous cross sections not considered by the authors, reinforce the need to revise critically the procedures on which the usual DINS data analysis is based as well as the proper characterisation of the experimental set-up.

physics.data-an

Multiple scattering and attenuation corrections in Deep Inelastic Neutron Scattering experiments

Multiple scattering and attenuation corrections in Deep Inelastic Neutron Scattering experiments are analyzed. The theoretical basis is stated, and a Monte Carlo procedure to perform the calculation is presented. The results are compared with experimental data. The importance of the accuracy in the description of the experimental parameters is tested, and the implications of the present results on the data analysis procedures is examined.

physics.data-an

Formalism for obtaining nuclear momentum distributions by the Deep Inelastic Neutron Scattering technique

We present a new formalism to obtain momentum distributions in condensed matter from Neutron Compton Profiles measured by the Deep Inelastic Neutron Scattering technique. The formalism describes exactly the Neutron Compton Profiles as an integral in the momentum variable $y$. As a result we obtain a Volterra equation of the first kind that relates the experimentally measured magnitude with the momentum distributions of the nuclei in the sample. The integration kernel is related with the incident neutron spectrum, the total cross section of the filter analyzer and the detectors efficiency function. A comparison of the present formalism with the customarily employed approximation based on a convolution of the momentum distribution with a resolution function is presented. We describe the inaccuracies that the use of this approximation produces, and propose a new data treatment procedure based on the present formalism.

physics.data-an