Speaker
Description
This study presents the improved results of thermal neutron beams at horizontal channels No. 2 and No. 3 of the Dalat Nuclear Research Reactor (DNRR)- Viet Nam, by replacement of the original silicon crystal filters with sapphire C-plane (0001) crystal rods. The filter configurations were investigated through neutron spectrum calculations as a function of filter length using the FILTER-8 and MCNP codes, with thermal neutron cross-section data generated by NJOY2016. The phonon density of states (PDOS) of sapphire was calculated using the PHONOPY program. Calculation results indicated that a sapphire crystal length of 20 cm provides the best enhancement of the thermal neutron flux and cadmium ratio (RCd) values in both channels. Experimentally, the thermal neutron fluxes increased by factors of 3.24 for both channels No. 2 and No. 3, while the corresponding RCd values improved by factors of 2.82 and 17.91. These findings demonstrate the effectiveness of sapphire crystal filters in reactor-based thermal neutron beam purification, with significant implications for research, applications, and education.
