Simulation of a collimator and sapphire filter for PGAA facility of the Moroccan TRIGA MARK II research reactor

Highlights: • Impact Sapphir (Al2O3) filter in components of the neutron beam. • Design of the collimator for PGAA. • Simulation of the collimator with Monte Carlo N-Particle code MCNP6.2 • Generate thermal neutron treatment file $S(\alpha ,\beta )$ for Sapphir (Al2O3) using LEAPR/NJOY2016 - Abstract: The Prompt Gamma Neutron Activation Analysis (PGAA) facility will be commissioned at the NB1 beam tube of the Moroccan TRIGA MARK II research reactor. PGAA is a non-destructive analytical technique used for multi-elemental analysis and especially for light element analysis. For better performances, PGAA requires small and focused beam, and high Φ_th/Φ_ep and Φ_th/Φ_fast ratios, and low background gamma radiation. For this purpose, fast neutron filters are commonly used to reduce fast and epithermal components of neutron flux. In this paper, the impact of sapphire filter, introduced, within the collimator hole, at the beam port on neutron spectra was evaluated. Monte Carlo, MCNP6.2, code has been used with ENDF VII.1 neutron cross section library to perform this study. An approximate TRIGA MARK II reactor MCNP model has been used to generate neutron spectra at the entrance of the collimator. Then an independent model for both collimator and sapphire filter has been brought into calculation to fulfil our purpose. Results showed an increase of about 8 times for both Φ_th/Φ_ep and Φ_th/Φ_fast ratios using a 10 cm length of sapphire.