A matrix to correct for K-edge escape and Compton scatter in X- and gamma -ray detectors

Abstract

The fraction of X- and gamma -ray photons that give rise to a K-edge escape photon of iodine as a function of photon energy is derived for a NaI(Tl) detector from published values in the literature and confirmed by experimental measurement for a 2*2 inch detector. These values are used to derive a matrix describing the K-edge escape of iodine for NaI(Tl) photon detectors. The fraction of Compton photons scattered into each lower energy channel as a function of incident photon energy is measured utilizing monoenergetic photon sources. From these measured values, a matrix is derived that described the effects of Compton scatter in the crystal as a function of incident photon energy. The matrix Ekj(E), describing K-edge escape photons, and the matrix, Skj(E), describing Compton scatter, are combined to form the matrix Ckj(E), describing both escape and Compton scattered photons.