Fast-neutron induced background in LaBr_3 :Ce detectors

摘要

The response of a scintillation detector with a cylindrical 1.5-in. LaBr_3 :Ce crystal to incident neutrons has been measured in the energy range E_n = 2-12 MeV. Neutrons were produced by proton irradiation of a Li target at E_p = 5-14.6 MeV with pulsed proton beams. Using the time-of-flight information between target and detector, energy spectra of the LaBr_3 :Ce detector resulting from fast neutron interactions have been obtained at 4 different neutron energies. Neutron-induced y rays emitted by the LaBr_3 :Ce crystal were also measured in a nearby Ge detector at the lowest proton beam energy. In addition, we obtained data for neutron irradiation of a large-volume high-purity Ge detector and of a NE-213 liquid scintillator detector, both serving as monitor detectors in the experiment. Monte-Carlo type simulations for neutron interactions in the liquid scintillator, the Ge and LaBr_3 :Ce crystals have been performed and compared with measured data. Good agreement being obtained with the data, we present the results of simulations to predict the response of LaBr_3 :Ce detectors for a range of crystal sizes to neutron irradiation in the energy range E_n = 0.5-10 MeV.