Modeling and Design of a Gadolinium Based Neutron Detector

The goal is to measure the partial cross sections for ($\gamma $, xn) and ($\gamma $, f) on the actinides with the ultimate objective of developing and refining a method for the $\gamma $-ray interrogation of fissionable material. These measurements require the construction of a highly segmented neutron detector to record multiple neutrons emitted following photodisintegration and fission. Each detector segment will use a gadolinium-loaded liquid organic scintillator optically coupled to a photomultiplier tube. Gadolinium has one of the highest thermal neutron capture cross sections (49 kb), therefore its presence in the detector will greatly enhance neutron detection efficiency. A prototype detector of 3 L volume has been constructed and modeled using Geant4, a Monte Carlo based program.\footnote{S.Agostinelli et al., \textit{Nucl. Instr. and Meth}. \textbf{A}506, 250, (2003).} The detector model and conclusions developed from it along with the results from testing the prototype detector will be presented.