Embedded underwater front-end electronics for the 3-inch photomultipliers in the JUNO experiment
Abstract
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator-based, low-radioactivity, multi-purpose neutrino detector located 693 meters (1800 m.w.e.) underground in the Guangdong province, China. To detect scintillation light produced in the target, the detector is equipped with 17,612 20-inch photomultipliers (PMTs), forming the Large PMT system (LPMT). In addition, 25,600 3-inch photomultipliers (the Small Photomultiplier System or SPMT) are deployed in the gaps between the LPMTs. This paper presents the design and performance of the underwater front-end electronics developed for the SPMT system. It details the individual electronics boards and their key components, the inter-board interfaces, the system-level design, and the firmware architecture that supports data acquisition and control. It also outlines mechanical and thermal integration, board validation procedures, and system performance metrics. The readout chain includes digitization of 128 PMT channels per unit, synchronized time-stamping, charge measurement, event packaging, and bandwidth management. Comprehensive validation confirms the system's readiness to meet JUNO's stringent physics goals. The underwater electronics achieve noise levels as low as 0.04 photoelectrons with minimal crosstalk (below 0.4%) and a bandwidth of 57 MB/s, ensuring reliable single photo-electron detection and operation under high-rate conditions. The SPMT system has now been fully integrated and installed in JUNO. Its commissioning and physics performance will be reported in a future publication.
Keywords
Cite
@article{arxiv.2604.25835,
title = {Embedded underwater front-end electronics for the 3-inch photomultipliers in the JUNO experiment},
author = {Cedric Cerna and Miao He and Xiaoshan Jiang and Juan Pedro Ochoa-Ricoux and Frederic Perrot and Angel Abusleme and Thomas Adam and Fengpeng An and Costas Andreopoulos and Giuseppe Andronico and Joao Pedro Athayde Marcondes de Andre and Nikolay Anfimov and Vito Antonelli and Tatiana Antoshkina and Didier Auguste and Nikita Balashov and Andrea Barresi and Davide Basilico and Eric Baussan and Marco Beretta and Antonio Bergnoli and Svetlana Biktemerova and Thilo Birkenfeld and Simon Blyth and Manuel Boehles and Anastasia Bolshakova and Mathieu Bongrand and Clement Bordereau and Matteo Borghesi and Dominique Breton and Augusto Brigatti and Riccardo Brugnera and Riccardo Bruno and Antonio Budano and Jose Busto and Marcel Buchner and Anatael Cabrera and Barbara Caccianiga and Hao Cai and Xiao Cai and Yi-zhou Cai and Stephane Callier and Antonio Cammi and Augustin Campeny and Guofu Cao and Jun Cao and Yaoqi Cao and Rossella Caruso and Nunzio Giudice and Maxim Gonchar and Guanda Gong and Guanghua Gong and Yuri Gornushkin and Marco Grassi and Maxim Gromov and Vasily Gromov and Minhao Gu and Xiaofei Gu and Yu Gu and Mengyun Guan and Yuduo Guan and Nunzio Guardone and Rosa Maria Guizzetti and Cong Guo and Wanlei Guo and Caren Hagner and Hechong Han and Yang Han and Chuanhui Hao and Vidhya Thara Hariharan and Wei He and Xinhai He and Tobias Heinz and Patrick Hellmuth and Yuekun Heng and Rafael Herrera and YuenKeung Hor and Shaojing Hou and Fatima Houria and Gerard Claverie and Catia Clementi and Barbara Clerbaux and Claudio Coletta and Davide Chiesa and Pietro Chimenti and Ziliang Chu and Artem Chukanov and Marta Colomer Molla and Fabio Mantovani and Stefano M. Mari and Agnese Martini and Johann Martyn and Matthias Mayer and Davit Mayilyan and Yue Meng and Anselmo Meregaglia and Lino Miramonti and Michele Montuschi and Iwan Morton-Blake and Xiangyi Mu and Lakshmi Murgod and Massimiliano Nastasi and Dmitry V. Naumov and Elena Naumova and Igor Nemchenok and Elisabeth Neuerburg and Alexey Nikolaev and Feipeng Ning and Zhe Ning and Yujie Niu and Hiroshi Nunokawa and Lothar Oberauer and Sebastian Olivares and Alexander Olshevskiy and Domizia Orestano and Fausto Ortica and Rainer Othegraven and Yifei Pan and Alessandro Paoloni and George Parker and Yatian Pei and Luca Pelicci and Anguo Peng and Yu Peng and Zhaoyuan Peng and Elisa Percalli and Willy Perrin and Fabrizio Petrucci and Oliver Pilarczyk and Artyom Popov and Pascal Poussot and Ezio Previtali and Fazhi Qi and Ming Qi and Sen Qian and Xiaohui Qian and Zhaoxiang Wu and Zhi Wu and Michael Wurm and Jacques Wurtz and Dongmei Xia and Shishen Xian and Ziqian Xiang and Fei Xiao and Pengfei Xiao and Tianying Xiao and Xiang Xiao and Wei-Jun Xie and Xiaochuan Xie and Yuguang Xie and Zhizhong Xing and Benda Xu and Cheng Xu and Chuang Xu and Donglian Xu and Fanrong Xu and Jiayang Xu and Jilei Xu and Jinghuan Xu and Meihang Xu and Shiwen Xu and Xunjie Xu and Dongyang Xue and Jingqin Xue and Baojun Yan and Qiyu Yan and Taylor Yan and Xiongbo Yan and Changgen Yang and Chengfeng Yang and Fengfan Yang and Jie Yang and Kaiwei Yang and Lei Yang and Pengfei Yang and Xiaoyu Yang and Xuhui Yang and Zekun Yang and Haifeng Yao and Jiaxuan Ye and Mei Ye and Ziping Ye and Frederic Yermia and Jilong Yin and Weiqing Yin and Xiaohao Yin and Zhengyun You and Boxiang Yu and Chiye Yu and Chunxu Yu and Hongzhao Yu and Peidong Yu and Simi Yu and Zeyuan Yu and Cenxi Yuan and Noman Zafar and Jilberto Zamora and Vitalii Zavadskyi and Fanrui Zeng and Shan Zeng and Tingxuan Zeng and Liang Zhan and Bin Zhang and Feiyang Zhang and Han Zhang and Hangchang Zhang and Haosen Zhang and Honghao Zhang and Jiawen Zhang and Jie Zhang and Jingbo Zhang and Junwei Zhang and Lei Zhang and Ping Zhang and Qingmin Zhang and Rongping Zhang and Shiqi Zhang and Shuihan Zhang and Tao Zhang and Xiaomei Zhang and Xu Zhang and Xuantong Zhang and Yibing Zhang and Yinhong Zhang and Yiyu Zhang and Yongpeng Zhang and Yuanyuan Zhang and Yumei Zhang and Zhicheng Zhang and Zhijian Zhang and Jie Zhao and Runze Zhao and Shujun Zhao and Yangheng Zheng and Li Zhou and Shun Zhou and Xiang Zhou and Xing Zhou and Jingsen Zhu and Kangfu Zhu and Kejun Zhu and Bo Zhuang and Honglin Zhuang and Jiaheng Zou},
journal= {arXiv preprint arXiv:2604.25835},
year = {2026}
}