investigation of pyrolytic graphite single-crystal (002) plane fine tuning effect on the reflected monochromatic neutron spectra

Single-crystal graphite grown in highly preferred orientation of (002)-planes known as pyrolytic graphite is used in many research centers to make monochromatic neutron beam the exited neutrons from the radial beam channels of the research reactors. simulation methods could be effectively used to predict the crystal behavior before time-consuming and high-cost experimental tests. the present work aims to investigate the effect of the pg(002) crystal fine tuning on the reflected neutron spectra quality in tehran research reactor (trr) d channel neutron beam line. hence, vitess3.4 and mcstas neutron optic-based computational codes were used in the present work to study the mentioned parameter. to evaluate the obtained code data accuracy a benchmark study was carried out in the present work. the obtained simulations showed that fine adjustment of the crystal angle than the parallel incident neutron beam is very important. in addition, the crystal mosaic spread has noticeably effect on the reflected neutron intensity so that its change from 1.0 to 0.5 decreases the monochromatic neutron peak intensity about 12%. in addition, the simulations showed the crystal reflectivity change from 1 to 0.7 could decrease the monochromatic neutron peak intensity about 43%. comparison of the experimental monochromatic reflected beam from pg(002) crystal with the carried out simulations showed there is good agreement between the two obtained spectra.