Design and Verification of the JUNO Liquid Filling Control System

TL;DR

The paper presents the design, implementation, and verification of a high-reliability liquid Filling, Overflow, and Circulation (FOC) control system for JUNO, built on a PLC-based architecture with precision sensors and actuators. It integrates PID regulation, sequential logic, and safety interlocks across a four-layer system (sensor, controller, actuator, alarm/data management) and interfaces local HMI with EPICS for global detector control. Commissioning and test results with both pure water and liquid scintillator demonstrate flow-setpoint accuracy within 0.5% and rapid stabilization within minutes, validating robust performance and safety. The work offers a scalable reference for large underground fluid control experiments and outlines potential future enhancements such as model predictive control and machine learning-based diagnostics for extended reliability and performance.

Abstract

Jiangmen Underground Neutrino Observatory (JUNO) is a large-scale neutrino experiment with multiple physics goals including neutrino mass hierarchy, accurate measurement of neutrino oscillation parameters, neutrino detection from supernova, sun, and earth, etc. This paper presents the design, implementation, and verification of a high-reliability automated control system for the liquid Filling, Overflow, and Circulation system in the JUNO experiment. The system is built upon a Programmable Logic Controller architecture, integrated with high-precision sensors and actuators. It implements advanced control strategies, including Proportional-Integral-Derivative regulation, sequential logic, and safety interlocks, to achieve closed-loop control of critical parameters such as flow rate, liquid level, and pressure. Commissioning tests with both pure water and liquid scintillator demonstrate the system's exceptional performance, achieving flow control stability within 0.5% of the setpoint with a rapid stabilization time. The robust design, featuring hardware redundancy and software safeguards, ensures the system meets the stringent requirements for the safe filling and long-term stable operation of JUNO's 20-kiloton central detector and provides a scalable reference for large underground fluid control experiments.

Figures (5)

• Figure 1: Primary P&ID of the FOC system
• Figure 2: Layout of the control system
• Figure 3: HMI based on TIA Portal
• Figure 4: WP and CD filling automatic control at test stage
• Figure 5: Liquid level changes during the test with LS purification system