Monte Carlo-based correction of scattering effects in low-energy mass attenuation experimental measurements of...

Low-energy gamma-ray attenuation measurements are strongly influenced by coherent (Rayleigh) scattering and geometrical effects, particularly under non-ideal broad-beam experimental conditions. In this work, a Monte Carlo-based correction methodology using the MCNP6 code was developed to improve the accuracy of mass attenuation coefficient measurements in 3D-printed polymeric materials. Experimental measurements were performed for acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol (PETG), and polylactic acid (PLA) using ²⁴¹Am and ¹³⁷Cs gamma-ray sources in combination with a 2 × 2″ NaI(Tl) scintillation detector. Monte Carlo simulations were conducted to reproduce both the experimental measurement geometry and an idealized narrow-beam configuration, enabling the determination of correction factors for low-energy attenuation measurements affected by scattering effects. Additional simulations were performed within the 40-100 keV energy range to develop mathematical fitting functions capable of estimating scattering and geometrical corrections as a function of photon energy. Aluminum samples were also analyzed as a reference material to validate both the experimental methodology and the MCNP6 simulations. The obtained attenuation coefficients were compared with NIST XCOM reference data, showing maximum deviations of 4.94% for the ¹³⁷Cs measurements (aluminum) and 9.50% for the corrected ²⁴¹Am measurements (PLA). Results demonstrated that the proposed correction methodology significantly improved agreement between experimental and reference attenuation coefficients, particularly for low-energy photons strongly affected by Rayleigh scattering and geometrical effects. The proposed approach enables reliable attenuation measurements to be performed even under non-ideal experimental conditions, particularly in laboratories without access to highly collimated measurement systems or high-intensity radioactive sources. This methodology contributes to the assessment of 3D-printed polymers as alternative materials for radiation shielding and nuclear technology applications.