MgO single-crystal as an efficient thermal neutron filter

Abstract: A formula is given which, for neutron energies in the range 10−4 < E <10eV, permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of magnesium oxide (MgO) temperature and crystal parameters. Computer program has been developed to calculate the total neutron cross-section and transmission through mono-crystalline MgO. The calculated neutron transmission and effective attenuation coefficient values for MgO-single crystal at different temperatures are compared with measured ones. An overall agreement is indicated between the formula fits and experimental data. A feasibility study for the use of MgO-single crystal is discussed in terms of the optimum MgO-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accompanying fast neutrons and gamma rays. Calculation shows that 10cm thick MgO-single crystal cut along its (100) plane, with 0.5° FWHM on mosaic spread and cooled at 77K, is a good thermal neutron filter, with high effect-to-noise ratio. [Copyright &y& Elsevier]