Monte Carlo Simulation Model of the Dingo Thermal Neutron Imaging Beamline at ANSTO

This work presents an experimentally validated Monte Carlo simulation model of the Dingo thermal neutorn beamline at the Austrlian Centre for Neutron Scattering (ACNS). The model was constructed using CAD drawings of the entire beam transport system and its material composition. The neutron spectrum was refined using in-beam nuetron activation analysis and outof-beam Bonner sphere spectroscopy. A sapphire filter was implemented and evaluated against experimental results. The model achieved good agreement with experimental data, with simulated neutron beam profiles within 2.3% and 1.6% of gold wire measurements at the tertiary sutter and sample stage, respectively. The refined neutron spectrum consists of 63.5% thermal, 16.2% epithermal and 20.2% fast neutrons, while the beam filtered by the sapphire filter constitutes 981% thermal neutron, and a decreased the thermal neutron flux by approximately 45%. Out-of-beam neutron spectra and counts root mean square errors (RMSE) were within $5.0+/-1.4 \%$ and $9.1+/-0.5 \%$, respectively. The model’s accuracy and flexibility offer advantages to Dingo users and the neutronics community.