Neutron transmission probability through a revolving slit for a continuous source and a divergent neutron beam

An analytical calculation for the transmission probability of neutrons travelling through a revolving slit is presented here. For the first time, two effects have been taken into account in the same approach, that is, on the one hand, the fact that the neutron beam might be divergent and, on the other hand, that neutrons from a continuous source can arrive at different times at the chopper. Furthermore, the neutron distribution at a given distance behind the chopper has been calculated and these theoretical results have been compared with simulated data obtained with the VITESS simulation program. The theoretical and the simulated curves are in good agreement.