Gamma-ray attenuation and spectral-angular transport in transparent graded-Z multilayer shields

Area of Science:

• Materials Science
• Nuclear Engineering
• Medical Physics

Background:

• Transparent radiation shields are crucial for medical imaging, nuclear medicine, and radiation monitoring.
• Existing shields face limitations in balancing photon attenuation and secondary emission, especially in the 0.06-1.33 MeV range.

Purpose of the Study:

• To evaluate a novel graded-Z multilayer transparent radiation shield composed of bismuth-rich borosilicate (BBS), lutetium aluminum garnet (LuAG), and silica (SiO2).
• To compare its performance against commercial RS-253 glass and literature-based Bi2O3 systems using Monte Carlo simulations.

Main Methods:

• GEANT4 Monte Carlo simulations were employed to model photon transport through the graded-Z multilayer and RS-253 glass.
• Mass attenuation coefficients, half-value layers, spectral fluorescence, and angular transmission were analyzed.
• Performance was benchmarked against commercial materials at matched areal density.

Main Results:

• The graded-Z multilayer demonstrated higher mass attenuation coefficients and reduced half-value layers across the studied energy range.
• Spectral analysis revealed energy-dependent fluorescence due to Bi and Lu K-edges.
• Enhanced forward-directed transmission was observed at higher energies compared to RS-253 glass.

Conclusions:

• The graded-Z shielding design offers enhanced attenuation beyond compositional optimization.
• It modifies photon transport spectrally and directionally, presenting a tradeoff between attenuation and energy leakage.
• The study provides a framework for evaluating transparent graded-Z shielding, with experimental validation recommended.