Analytical Method to Generate the Response Matrix Cross Correlations Used in the Passive Coincidence Shape Unfolding Technique for Plutonium Objects

A measurement technique was developed to extract the general shape of a plutonium object containing 240Pu using second order cross correlations and the nonnegative least squares (NNLS) algorithm. This technique relies on the use of a response matrix composed of the detector-detector cross correlations for four detectors arranged in a tetrahedron about the object being measured. For this work, the response matrix was empirically measured but work towards analytically generating this matrix was begun. This paper will show a method of generating the detector-detector cross correlations.