Modified Uniformly Redundant Array coded aperture design by MCNP simulation for neutron imaging with Timepix

Accurate identification of radioactive hotspots is essential to the nuclear industry, especially for decommissioning operations, waste management, radiation protection, nuclear research, and homeland security applications. In certain cases, the detection of fast neutron emissions is particularly important when gamma imaging techniques reach their limits. CEA List presented a highly compact, (19 × 14 × 15) cm 3 and 2.2 kg, fast neutron/gamma imager based on a Modified Uniformly Redundant Array coded aperture, a Timepix detector enhanced with of a paraffin layer and specific processing algorithms. A first prototype was designed and the feasibility of coded aperture fast neutron imaging was demonstrated with these technologies integrated in the GAMPIX gamma camera prototype. However, the fast neutron imaging capability has not yet been fully evaluated and optimized in terms of encoding capacity, field of view and angular resolution. This paper presents a comprehensive analysis of how coded aperture characteristics—such as material, rank, and thickness—affect the imaging performance of our fast-neutron imager using Monte Carlo simulations. The study highlights the significant impact these parameters have on sensitivity, spatial resolution, and field of view, thereby contributing to the optimization of neutron imaging systems and filling an important gap in existing research. • Tungsten was identified as the optimal material for encoding neutron flux • Rank 7 MURA aperture is the ideal balance between detection and resolution • Thickness aperture may have a significant impact on the field of view