Suren Kandasamy Dissertation.pdf - University of Surrey

M.Sc Dissertation(A)(B)Figure 2.1 Scintillation emission spectrum of the (A) LaCl 3 :Ce and (B)LaBr 3 :Ce crystal [16]2.3 Gamma-Ray InteractionsA gamma-ray will interact with its medium in one of three different ways:photoelectric absorption, Compton scattering, and pair production. All these processlead to the partial or complete transfer of the gamma-ray photon energy to electronenergy [1]. These different interactions change their probability of occurring dependingon the energy of the gamma-ray and the atomic number of the material.As can be seen from Fig. 2.2, the line at the left represents the energy at whichphotoelectric absorption and Compton scattering are equally probable as a function ofthe absorber atomic number. The line at right represents the energy at which Comptonscattering and pair production are equally probable. The photoelectric effect isdominant for low energy photons and high Z materials. Pair production is dominant forhigh energy photons and high Z materials. The Compton scattering interaction isdominant for moderate energies. Compton continuum will be observed at the lowerenergy end of the spectrum.K. Suren 6