Designing a combined guide and investigating the role of collimator in neutron intensity uniformity

The present study investigates the effect of some geometrical parameters on the performance of the neutron guide system, including the length of the collimator and the angle between successive guides. This study investigates the use of optical components to remove fast neutrons in straight and angled guides, and their role in focusing the neutron beam and increasing the intensity uniformity on the sample. In this research, the McStas code, which was developed with the Monte Carlo method, was used. The effect of the length of the collimator on the creation of a neutron beam with a certain energy, and the uniformity of the intensity of the beam at the sample location have been investigated. For angled guides, the intensity of the neutron beam and its uniformity at the sample location, in terms of the angle of the guides with each other, were calculated using McStas and Vitess codes and the results were compared with each other. Calculations have been done using an americium-beryllium source with an intensity of about 5 Curie. The results show that the combination of two convergent and divergent collimators have greater ability to uniform the neutron intensity than the linear collimator.