The Design and Sensitivity of JUNO's scintillator radiopurity pre-detector OSIRIS

TL;DR

This paper details the design, simulation, and measurement strategies of the OSIRIS detector, a subsystem of JUNO, aimed at ensuring scintillator radiopurity at extremely low contamination levels to support neutrino detection.

Contribution

It presents the design, simulation, and sensitivity analysis of the OSIRIS detector for measuring ultra-low levels of uranium and thorium in JUNO's scintillator.

Findings

Designed a 20 m³ detector with ultralow background levels.

Achieved sensitivity to $10^{-16}$ g/g of $^{238}$U and $^{232}$Th.

Developed measurement strategies for radiopurity validation.

Abstract

The OSIRIS detector is a subsystem of the liquid scintillator fillling chain of the JUNO reactor neutrino experiment. Its purpose is to validate the radiopurity of the scintillator to assure that all components of the JUNO scintillator system work to specifications and only neutrino-grade scintillator is filled into the JUNO Central Detector. The aspired sensitivity level of $10^{-16}$ g/g of $^{238}$U and $^{232}$Th requires a large ($\sim$20 m$^3$) detection volume and ultralow background levels. The present paper reports on the design and major components of the OSIRIS detector, the detector simulation as well as the measuring strategies foreseen and the sensitivity levels to U/Th that can be reached in this setup.