Estimation of Bonner sphere cross-talking with Monte Carlo method and spectrometer calibration with 241Am-Be neutron source

There are usually two kinds of experiment methods for neutron spectrum measurement by Bonner sphere spectrometer (BSS). The first is to use only one Bonner sphere (BS) at a time to complete the neutron experiment by repeated measurements; The other is to measure multiple Bonner spheres (BSs) together, and this multi-sphere simultaneous measurement method can complete the neutron experiment only once. The single sphere measurement method cannot guarantee that the measurement environment is completely consistent every time, which leads to inevitable measurement errors. The multi-sphere simultaneous measurement method can ensure the same experimental environment for each sphere, but there will be cross-talking. This paper studies the influence of cross-talking on BSS. Firstly, we use Geant4 to simulate the corresponding neutron response function with and without cross-talking, and analyze the error between the two neutron response functions. Secondly, the neutron count of

neutron source experiment is simulated. Considering that the BSS is close to the floor, the neutron counting error of BS with and without cross-talking and floor scattering is calculated. Finally, we actually measure the

neutron source using a BSS and obtain 8 neutron counts. The spectrum of

neutron source is obtained by calibrating the influence of cross-talking. The results show that the scattered neutrons which affect the count of BS are mainly the primary scattered neutrons, which account for more than 90% of all scattered neutrons. The scattered neutrons mainly affect the neutron response function of the large BS in the high energy domain and the small BS in the low energy domain. The cross-talking has a great influence on the neutron count of large and small BS, while the floor scattering has a great influence only on the small BS. The

neutron spectrum obtained by calibrated neutron counts is more accurate than that obtained by the original experiment counts. Especially in the range of 1$\sim$5 MeV, the calibrated

neutron spectrum is much closer to the international standard spectrum. The mean square error (RMSE) of calibrated

neutron spectrum is reduced by 3.86%. In this paper, by analyzing the influence of cross-talking, the neutron count of BSS is calibrated, and the accuracy of

neutron spectrum is improved, which provides a strong basis for unfolding neutron spectrum.