کوروش قیصری

In this thesis, a new method for calculation ultra-cold neutron (UCN) production rate is presented. A super-thermal source (UCN source) consisted of three main parts: moderator, converter and spallation target. The D2O was investigated as moderator, and sD2 as the converter .The spallation target was a combination of Lead, heavy water and zirconium. In order to determine the required parameters, a two-dimensional (2D) neutron balance equation written in Matlab was combined with the MCNPX simulation code. The 2D neutron-transport equation in cylindrical (\rho-z) coordinate was solved for 330 neutron energy groups in the sD2 by using simulated CN flux as boundary value. In the present multi-group calculation, a converge result was achieved with suitable space steps. The space steps and were determined to be about 0.04 and 0.2cm, respectively. In the optimal condition, the average UCN flux and the average UCN production rate was calculated as 6.79e6 cm-2s-1 and 2.20e5 cm-3s-1, respectively. The comparison of obtained results for UCN production rate and the experimental results show that our method has good ability.