Assessment of sapphire crystal performance with different crystal planes (111) and (112) in neutron and gamma...

Research reactors beamlines have extensively used neutron filter crystals worldwide for 3 decades. However, there is a lack of sufficient experimental tests to show their neutron or gamma filtering performance in front of different neutron or gamma sources with different energy spectra. The present work has been planned to experimentally investigate two 111 and 112 crystallographic-grown sapphire crystals with the neutron spectrum of the vertical beam channel of the MNSR reactor as well as with ⁶⁰Co and ¹³⁷Cs gamma point sources. The obtained results showed the crystals agree within 0.7 % for fast neutron (E_n > 0.5 eV) filtering while both of them filter about 39 % of neutrons in 2.5 cm thickness. While 112 crystallographic-grown sapphire transmission rate of thermal neutrons is 14.4 % higher than 111 crystallographic-grown sapphire. Also, this study showed there is good conformity between the obtained data in this work and other theoretical and experimental data while all show at least 74 % of fast neutron intensity (E_n > 0.5 eV) could be removed using 7.5 ± 0.1 cm sapphire crystal. The findings show that there is not noticeable reduction of thermal neutrons (E_n < 0.5 eV); about 8 % using a 2.5 cm crystal up to 24 % using a high thickness of about 7.5 cm. Also, as a result of the high density of the sapphire crystal, its gamma shielding performance is 4 times more than the thermal neutron transparent metallic aluminum sample with the same thickness.