<title>Estimation of neutron optical characteristics of capillaries of different shapes</title>

Abstract

Calculation of neutron optical system characteristics should be done with regard to the fact that the sources of thermal neutrons are lengthy objects. Hence, when neutrons pass through the capillaries in neutron optical system (CNOS), there may be a considerable contribution to the total fluence, made by neutrons going along helix-shaped trajectories with angle with the capillary axis exceeding the critical reflection angle. Algorithm has been developed permitting calculation of capillaries' transmission, impact of bending capillaries and their radius variation along the length, as well as angular distribution of radiation output. Monte-Carlo method allows calculation of capillaries with any shape of radius variations. Comparison of calculated and experimental data provides assessment of the quality of CNOS manufacture.