Implementation of the World's Largest Liquid Scintillator Detector and Its Radioactivity Background Measurement

by Mr Jiajun Li (中山大学)

Thursday 23 Apr 2026, 10:00 → 11:30 Asia/Shanghai

5#/6th-603 - Meeting Room 603 (Science Building)

Abstract:

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kiloton liquid scintillator (LS) detector built to determine the neutrino mass hierarchy and achieve precision measurements of neutrino oscillation parameters. Its rich physics program also includes solar neutrinos, supernova neutrinos, geoneutrinos, and atmospheric neutrinos. Achieving these goals requires both an unprecedentedly large and ultrapure LS target, as well as a thoroughly characterized radioactive background environment. This talk presents my core contributions to the JUNO experiment, spanning detector commissioning to first physics results, with a focus on the detector filling and background analysis. I will describe the design and operation of the Filling, Overflow and Circulation (FOC) system, which completed the filling of the world's largest LS detector with high precision, high safety, a high degree of automation, and exceptional radiopurity preservation. Real-time monitoring during filling revealed LS stratification due to temperature differences. I will then present a systematic analysis of key radioactive backgrounds. Using 214BiPo, 212BiPo, and 210Po as probes, I quantified the intrinsic 238U and 232Th concentrations at the 10−17 g/g level—directly verifying the ultra-high purity of JUNO's LS. These results establish a solid low-background foundation for JUNO's broad physics program.

Biography:

Jiajun Li is a PhD candidate in Physics at Sun Yat-sen University under the supervision of Professor Jiajie Ling. He specializes in neutrino physics, detector development, low-background measurement and liquid handling systems. During his doctoral studies, he has taken a leading role in the JUNO experiment, especially in detector filling and background characterization. During his master’s studies, he worked on dual-phase argon TPC detectors and liquid argon detector projects, where he also gained rich experience in cryogenic systems and safety design. He has accumulated comprehensive expertise in detector development, system integration and experimental operation.

Host: Prof. Yue Meng

Alternative online link：https://meeting.tencent.com/dm/EhxtwcIUit4k

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