کوروش قیصری

The paper presents a new approach to consider neutron moderation at large depths inside solid deuterium (sD2) converter of ultracold neutron (UCN) sources. One- and three-dimensional neutron balance equations have been solved in the Matlab program linked to the MCNPX computer code. To consider neutron moderation, neutron scattering kernels have been constructed and implemented into our calculations. Moreover, UCN source geometry has been improved in order to optimise the cold neutron flux inside the sD2 converter. The results indicate that the optimal length of the sD2 converter equals approximately 9 cm and most thermal neutrons are cooled near a depth of 15 cm.