Speaker
Description
The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose neutrino experiment whose primary objective is the determination of the neutrino mass ordering using a 20-kt liquid scintillator detector. During the filling phase, the Online Scintillator Internal Radioactivity Investigation System (OSIRIS) monitored the radiopurity of the liquid scintillator to ensure that the required contamination limits were met. OSIRIS is an 18-t liquid scintillator detector instrumented with 64 20-inch photomultiplier tubes and surrounded by a water Cherenkov detector providing an active muon veto. The detector is particularly sensitive to radioactive contaminants from the $^{232}\mathrm{Th}$ and $^{238}\mathrm{U}$ decay chains and exploits the characteristic delayed-coincidence signatures of the $^{212}\mathrm{Bi}\text{--}{}^{212}\mathrm{Po}$ and $^{214}\mathrm{Bi}\text{--}{}^{214}\mathrm{Po}$ decays to determine the corresponding isotope abundances. In addition, complementary analyses based on single-event spectra provide sensitivity to further intrinsic backgrounds. This poster presents the OSIRIS analysis framework and discusses the determination of liquid scintillator radiopurity, including constraints on U/Th-chain activity, radon activity, and contributions from $^{85}\mathrm{Kr}$ and $^{14}\mathrm{C}$, using both coincidence- and singles-based analyses.