Speaker
Description
The Back-End Card (BEC) is a crucial component in the trigger readout chain of the JUNO experiment, serving as the interface between approximately 7,000 Global Control Units (GCUs) and the central trigger system. A total of 163 BECs were installed for deployment in the experiment's underground environment. To support the system's expected long-term operation, we perform a reliability assessment based on historical data, including environmental monitoring (humidity and temperature), production quality control, and operational stability metrics. Statistical modeling methods, such as Weibull analysis, are applied to evaluate potential failure mechanisms and estimate reliability trends.
Summary (500 words)
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kt liquid scintillator detector under construction 700 m underground in southern China. Its primary goal is to determine the neutrino mass ordering using reactor antineutrinos, with additional sensitivity to solar, atmospheric, and supernova neutrinos. JUNO employs a dual PMT system with both 20-inch and 3-inch PMTs. The PMT electronics can be divided into two parts: the front-end electronics system performing analog signal processing under water (UW), and the back-end electronics system which consists of the DAQ and the trigger sitting outside water. A scheme of the Large-PMT trigger system is presented in Figure 1.
The back-end card (BEC) is a crucial component of JUNO's back-end electronics system and plays an important role in the trigger and clock system shown in Figure 2. It functions as a concentrator to collect and compensate for incoming trigger request signals. A Trigger/Timing Interface Mezzanine (TTIM) handles all the trigger request signals, and the hit signals from the various BECs are sent to Reorganize & Multiplex Unit (RMU) cards. The sum of the signals is then forwarded to the Central Trigger Unit (CTU), which makes the trigger decision based on the trigger logic and sends it to the Global Control Unit (GCU) via the RMU and the BEC. Given its central role and the extended expected operation time of JUNO, we have initiated a proactive study to evaluate the long-term reliability of the BEC under realistic environmental conditions.
The installation environment presents unique challenges for electronic equipment reliability. BECs are in a high-humidity underground Electronics room, where environmental measurements show relative humidity levels regularly exceeding 50% shown in Figure 3. and ambient temperatures ranging between 20–30°C. We analyze these environmental metrics against the BEC design specifications to identify potential reliability concerns.
This paper establishes a comprehensive framework for analyzing the long-term reliability of the BEC system in the challenging underground environment of the JUNO experiment. We examine potential failure mechanisms related to temperature and humidity variations that could affect electronic components within the BECs. The thermal considerations include component degradation through temperature cycling, while humidity factors encompass potential corrosion, electrical leakage, and condensation risks.
We discuss the theoretical impact of environmental factors on electronic devices, specifically focusing on BEC components such as FPGAs, connectors, and signal processing circuits. Based on industry standards, we assess the expected performance of BECs under varying environmental conditions.
This paper lays the groundwork for a comprehensive reliability study of the BEC system. As the JUNO experiment moves toward full operation, we will implement the monitoring frameworks described herein and collect long-term performance data. Future analysis will include failure rate predictions using Weibull distribution modeling and comparison of actual performance against theoretical expectations.
