Monte Carlo Simulation on Impact Factor of Scatter-photon in γ-ray Distance Detection

The gamma ray ranging technology based on scattered photons has the characteristics of high ranging accuracy, fast response speed, high reliability, small volume, light weight, etc., and is suitable for the height measurement with high precision in close range in harsh space environment. In this paper, the variation law of scattering photon energy and intensity under different conditions was simulated by MCNP program, and the relations between detection height, sourcedetector distance, γray energy, target thickness, target material, backscattering peak photon energy and intensity were analyzed for the specified principle model. The backscattering peak photon energy is independent of target thickness (>10 cm) and target material, positively correlated with ray energy and sourcedetector distance, and negatively correlated with the detection height. The photon intensity of the backscattering peak is independent of the target thickness (>10 cm), positively correlated with the detection height, and negatively correlated with ray energy, source-detector distance and target material. And for different target materials, the energy distribution interval of the simulated backscattering peak photon is consistent with that of the theoretical calculation, implying that the Monte Carlo simulation for gamma ray ranging technology is feasible and credible.