Target Mass Monitoring and Instrumentation in the Daya Bay Antineutrino Detectors

TL;DR

This paper details the design and implementation of a real-time monitoring system for the Daya Bay antineutrino detectors, ensuring precise measurement of the detector's target mass and environmental conditions during data collection.

Contribution

It introduces a comprehensive sensor system for continuous, in-situ monitoring of detector mass, temperature, and levelness, improving measurement accuracy in neutrino experiments.

Findings

Successful calibration and installation of sensors

Real-time data enables precise target mass determination

Enhanced detector stability and data quality

Abstract

The Daya Bay experiment measures sin^2 2{\theta}_13 using functionally identical antineutrino detectors located at distances of 300 to 2000 meters from the Daya Bay nuclear power complex. Each detector consists of three nested fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to overflow tanks on top of the detector to allow for thermal expansion of the liquid. Antineutrinos are detected through the inverse beta decay reaction on the proton-rich scintillator target. A precise and continuous measurement of the detector's central target mass is achieved by monitoring the the fluid level in the overflow tanks with cameras and ultrasonic and capacitive sensors. In addition, the monitoring system records detector temperature and levelness at multiple positions. This monitoring information allows the precise determination of the detectors' effective number of target protons during data taking. We present the design, calibration, installation and in-situ tests of the Daya Bay real-time antineutrino detector monitoring sensors and readout electronics.