Modeling the registration efficiency of thermal neutrons by gadolinium foils

In the paper we present the results of mathematical modeling of the registration efficiency of thermal neutrons for the converters made of natural Gd and its 157 isotope plane-parallel foils. In the performed calculations four fixed energies of neutrons with the corresponding wavelengths of 1, 1.8, 3 and 4 $A^0$ are taken into account. We calculate the efficiencies of the converter for electron escapes to frontward and backward hemispheres and their sum, depending on thickness of converting foils. Results of comparison of our calculations with the experimental data are presented.Comment: 19 pages, 8 figure

FERMI SURFACE TOPOLOGY BY THE TWO DIMENSIONAL ANGULAR CORRELATION OF ANNIHILATION RADIATION : COPPER, A TEST CASE

La surface de Fermi du cuivre, qui est bien connue, est utilisée pour examiner les performances d'un système de détection bi-dimensionnel de corrélations angulaires de la radiation d'annihilation du positron. Les structures attendues apparaissent dans nos résultats qui soulignent l'intérêt de cette technique pour l'étude des propriétés électroniques des métaux et de leurs alliages.The well known Fermi surface of copper is used to test a newly conceived two dimensional angular correlation of positron annihilation radiation apparatus. The results reveal the expected structure and outline the potential interest of this technique to study the electronic properties of metals and alloys