Monte Carlo Calculations of γ-Rays Angular Distribution Scattering from 11B in (γ, γ) Interaction

Abstract

An investigation of angular distribution of scattered gamma-rays is important to get information about an efficient arrangement of γ-ray detectors and it is necessary to design a real detection system of the inspection system by using a (γ, γ) interaction. Angular distribution of scattered gamma radiation from 11B at 4,440 keV from transition J π (5/2− → 3/2−) has been simulated by extended GEANT4. In the simulation, seven LaBr3:Ce detectors were recording the scattered photons from nuclear resonance fluorescence (NRF) process in a plane perpendicular to the incident polarized γ-ray beam. The γ-ray beam was assumed to be monoenergetic and linearly polarized with energy spread of 5%. All the LaBr3:Ce detectors were similar in the diameter of 1.5 in. and length of 3 in., positioned at seven different directions. Angular distribution of the scattered γ-rays is discussed in terms of the detectors’ positions with respect to the target and incident γ-ray beam. The result, which indicates the largest count rate from NRF signals is backward (135° and 225°) and forward (45° and 315°) directions with respect to the incident gamma-ray, is useful when using the NRF process in inspection of the special nuclear materials (SNM) like 235U and 239Pu.