Intrinsic background radiation of LaBr3(Ce) detector via coincidence measurements and simulations

The LaBr3(Ce) detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency. However, it has a relatively high intrinsic background radiation because of the naturally occurring radioisotopes in lanthanum, actinium, and their daughter nuclei. This limits its applications in low-counting rate experiments. In this study, we identified the radioactive isotopes in the phi 3 '' x 3 '' Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system. Moreover, we carried out a Geant4 simulation of the experimental spectra to evaluate the activities of the main internal radiation components. The total activity of the background radiation of B380 is determined to be 1.523 (34) Bq/cm(3). The main sources include La-138 at 1.428 (34) Bq/cm(3), Tl-207 at 0.0135 (13) Bq/cm(3), Bi-211 at 0.0136 (15) Bq/cm(3), Po-215 at 0.0135 (3) Bq/cm(3), Rn-219 at 0.0125 (12) Bq/cm(3), Fr-223 at 0.0019 (11) Bq/cm(3), Ra-223 at 0.0127 (10) Bq/cm(3), Th-227 at 0.0158 (22) Bq/cm(3), and Ac-227 at 0.0135 (13) Bq/cm(3). Of these, the activities of Tl-207, Po-211, Po-215, Fr-223, and Ac-227 are deduced for the first time from the secular equilibrium established in the decay chain of Ac-227.