Speaker
Description
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20-kton liquid scintillator detector designed to achieve a target energy resolution of 3% at 1 MeV through precise control of detector response and reconstruction systematics. Accurate three-dimensional positioning of calibration sources is a key requirement for this goal. JUNO employs an ultrasonic positioning system to determine the real-time spatial coordinates of calibration sources deployed by multiple calibration subsystems. The system consists of ultrasonic transmitters integrated with the sources and an array of fixed receivers on the inner surface of the center detector, enabling three-dimensional localization based on time-of-flight measurements. Using early commissioning and physics data, a typical three-dimensional positioning precision of about 5 cm is achieved across the central detector volume. These accurately determined source positions provide essential ground-truth inputs for PMT-based vertex reconstruction, leading to improved vertex resolution and, consequently, further enhancement of the energy resolution. The demonstrated performance satisfies the requirements of the JUNO calibration program and supports vertex reconstruction and high-precision energy.