“…The most important part of the collimator, the lining, should be made of a neutron absorbing material. In this study, three different materials that are often used as lining materials in thermal NR, namely, Cadmium, Gadolinium and Boral, were considered [8,11,13]. The divergent collimator is composed of a 0.5 cm layer of a lining material covered by a 3.5 cm layer of borated polyethylene (PE-B), while Bismuth (Bi) with 1 cm of thickness is used as the collimator casing.…”