Design of moderator and collimator for compact neutron radiography systems

Neutron radiography (NR) has been successfully implemented on reactors and accelerators in the past few decades. However, the promotion of NR is severely hindered by the immovability of the reactor neutron source. In order to solve this problem, the advanced neutron tube is employed as the neutron source of the compact NR system. To maintain the thermal neutron flux and reduce the gamma dose rate at the image plane, we give a novel design of moderator and collimator for the compact NR systems by using SuperMC software. Simulation results show that, under the neutron source yield of 1 × 10⁹ n ∕ s , we can obtain a uniform thermal neutron flux of 1 . 03 × 10^-5cm^-2 per source particle with n/ γ ratio of 2 . 47 × 10¹¹ ncm^-2Sv^-1 at the sample position by using the proposed moderator and collimator device, thus demonstrating its application potential in the compact NR systems.