Effect of ⁹Be Target Thickness on Neutron Production Using Reactor-Based Gamma Sources: A Monte Carlo Study with PHITS

This study uses Monte Carlo simulations with PHITS version 3.34 to examine the impact of beryllium (9Be) target thickness on photoneutron production. Continuous photon and neutron energy distributions were taken from the base of a radial piercing beam port to model the gamma source spectrum using a research nuclear reactor as a basis. Because of its high photonuclear cross-section, pure beryllium was chosen, and different target thicknesses were simulated in order to assess surface fluence and neutron yield. The findings demonstrate that neutron production within the material increases with beryllium thickness, with a significant peak seen at about 5 cm thickness. After this, internal neutron absorption and increased photon attenuation cause neutron production to decline. Thinner targets (less than 5 cm) had the highest neutron flux emitted from the surface, indicating how sensitive the neutron escape probability is to target geometry. These results support earlier research and emphasize how crucial it is to optimize target dimensions for applications requiring particular neutron energy ranges, like Boron Neutron Capture Therapy (BNCT). In order to optimize photoneutron sources for industrial and medical applications, the study recommends additional experimental validation and concludes that there is a trade-off between maintaining efficient neutron escape and optimizing neutron yield. Keywords: Photoneutron, gamma ray, reactor, beryllium, monte carlo, PHITS, BNCT