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arXiv · 2607.17509

Final assessment of radioactive impurities in the JUNO detector

Thomas Adam·Fengpeng An·Costas Andreopoulos·Giuseppe Andronico·Nikolay Anfimov·Vito Antonelli·Tatiana Antoshkina·João Pedro Athayde Marcondes de André·Didier Auguste·Nikita Balashov·Andrea Barresi·Davide Basilico·Eric Baussan·Marco Beretta·Antonio Bergnoli·Nikita Bessonov·Daniel Bick·Lukas Bieger·Svetlana Biktemerova·Thilo Birkenfeld·Simon Blyth·Manuel Böhles·Anastasia Bolshakova·Mathieu Bongrand·Matteo Borghesi·Dominique Breton·Augusto Brigatti·Riccardo Brugnera·Riccardo Bruno·Antonio Budano·Jose Busto·Marcel Büchner·Anatael Cabrera·Barbara Caccianiga·Hao Cai·Xiao Cai·Yi-zhou Cai·Stéphane Callier·Antonio Cammi·Guofu Cao·Jun Cao·Yaoqi Cao·Rossella Caruso·Cédric Cerna·Vanessa Cerrone·Jinfan Chang·Yun Chang·Tim Charisse·Chao Chen·Haotian Chen·Jiahui Chen·Jian Chen·Jing Chen·Junyou Chen·Pingping Chen·Shaomin Chen·Shiqiang Chen·Yixue Chen·Yu Chen·Ze Chen·Zhangming Chen·Zhiyuan Chen·Zhongchang Chen·Jie Cheng·Yaping Cheng·Yu Chin Cheng·Alexander Chepurnov·Alexey Chetverikov·Davide Chiesa·Ziliang Chu·Artem Chukanov·Gérard Claverie·Catia Clementi·Barbara Clerbaux·Claudio Coletta·Marta Colomer Molla·Selma Conforti Di Lorenzo·Chenyang Cui·Lorenzo Vincenzo D'Auria·Christophe De La Taille·Luis Delgadillo Franco·Ziyan Deng·Xiaoyu Ding·Xuefeng Ding·Yayun Ding·Sergey Dmitrievsky·Dmitry Dolzhikov·Chuanshi Dong·Haojie Dong·Jianmeng Dong·Marcos Dracos·Frédéric Druillole·Ran Du·Shuxian Du·Katherine Dugas·Stefano Dusini·Hongyue Duyang·Jessica Eck·Andrea Fabbri·Ulrike Fahrendholz

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) collaboration has completed the construction of the 20,000-ton liquid scintillator detector and the associated muon veto detector system. To meet the physics objectives, the materials used in the detector must exhibit low radioactive contamination. The single-event rate in the fiducial volume (R $<$ 17.2 m) of the scintillator is required to be approximately 7 Hz for energies above 0.7 MeV, resulting in an accidental coincidence background of about 1 event per day for reactor neutrino physics analyses. Since the beginning of the construction phase, we have screened the natural radioactivity content of thousands of materials, to select those that meet the design background budget. The radioactive impurity concentrations of the materials ultimately used in the JUNO detector are summarized in this paper. The construction of the entire detector and the subsequent filling of the liquid scintillator were completed in August 2025. From the initial data, the total count rate of natural radioactivity within the detector's fiducial volume has met the requirements and is sufficient to support the reactor antineutrino analysis.

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Thomas Adam, Fengpeng An, Costas Andreopoulos, Giuseppe Andronico, Nikolay Anfimov, Vito Antonelli, Tatiana Antoshkina, João Pedro Athayde Marcondes de André, Didier Auguste, Nikita Balashov, Andrea Barresi, Davide Basilico, Eric Baussan, Marco Beretta, Antonio Bergnoli, Nikita Bessonov, Daniel Bick, Lukas Bieger, Svetlana Biktemerova, Thilo Birkenfeld, Simon Blyth, Manuel Böhles, Anastasia Bolshakova, Mathieu Bongrand, Matteo Borghesi, Dominique Breton, Augusto Brigatti, Riccardo Brugnera, Riccardo Bruno, Antonio Budano, Jose Busto, Marcel Büchner, Anatael Cabrera, Barbara Caccianiga, Hao Cai, Xiao Cai, Yi-zhou Cai, Stéphane Callier, Antonio Cammi, Guofu Cao, Jun Cao, Yaoqi Cao, Rossella Caruso, Cédric Cerna, Vanessa Cerrone, Jinfan Chang, Yun Chang, Tim Charisse, Chao Chen, Haotian Chen, Jiahui Chen, Jian Chen, Jing Chen, Junyou Chen, Pingping Chen, Shaomin Chen, Shiqiang Chen, Yixue Chen, Yu Chen, Ze Chen, Zhangming Chen, Zhiyuan Chen, Zhongchang Chen, Jie Cheng, Yaping Cheng, Yu Chin Cheng, Alexander Chepurnov, Alexey Chetverikov, Davide Chiesa, Ziliang Chu, Artem Chukanov, Gérard Claverie, Catia Clementi, Barbara Clerbaux, Claudio Coletta, Marta Colomer Molla, Selma Conforti Di Lorenzo, Chenyang Cui, Lorenzo Vincenzo D'Auria, Christophe De La Taille, Luis Delgadillo Franco, Ziyan Deng, Xiaoyu Ding, Xuefeng Ding, Yayun Ding, Sergey Dmitrievsky, Dmitry Dolzhikov, Chuanshi Dong, Haojie Dong, Jianmeng Dong, Marcos Dracos, Frédéric Druillole, Ran Du, Shuxian Du, Katherine Dugas, Stefano Dusini, Hongyue Duyang, Jessica Eck, Andrea Fabbri, Ulrike Fahrendholz. 2026-07-20. Final assessment of radioactive impurities in the JUNO detector. https://arxiv.org/abs/2607.17509

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