Speaker
Description
Reflectors play an important role at reactor and spallation neutron sources, providing a means for otherwise lost neutrons to be potentially re-directed towards the neutron science instruments. Such materials typically surround the moderating volume, but can also be placed in the neutron beam extraction area. We present developments of improved modelling methods such as including crystallite effects in traditional beryllium reflectors [1] in addition to developments using the NJOY+NCrystal code for new proposed reflector materials such as Magnesium hydride and deuteride [2]. Of particular interest to very-cold and ultra-cold neutron sources is the possibility of using nanodiamonds in the neutron beam extraction area [2,3]. For the simulations of such a system, we present two alternative approaches. The first being the implementation of a small-angle neutron scattering model in OpenMC, to be combined with the standard bulk diamond ACE file and the second being the implementation of the small-angle scattering model inside NCrystal, which is then called directly during the Monte-Carlo simulation. In this work we present examples of cross-section computed for the above-mentioned materials and examples of Monte-Carlo calculations using the new developments.
This work was funded by the HighNESS project at the European Spallation Source. HighNESS is funded by the European Framework for Research and Innovation Horizon 2020, under grant agreement 951782.
[1] D.D. DiJulio et al., “Impact of crystallite size on the performance of a beryllium reflector”, Journal of Neutron Research, vol. 22, no. 2-3, pp. 275-279, 2020
[2] V. Santoro et al., “Development of high intensity neutron source at the European Spallation Source” Journal of Neutron Research, vol. 22, no. 2-3, pp. 209-219, 2020
[3] V. Nesvizhevsky, et al. "Fluorinated nanodiamonds as unique neutron reflector." Carbon, 130, 799-805, (2018).