Automated calibration system for a high-precision measurement of neutrino mixing angle θ13 with the Daya Bay antineutrino detectors

Abstract

We describe the automated calibration system for the antineutrino detectors in the Daya Bay Neutrino Experiment. This system consists of 24 identical units instrumented on 8 identical 20-ton liquid scintillator detectors. Each unit is a fully automated robotic system capable of deploying an LED and various radioactive sources into the detector along given vertical axes. Selected results from performance studies of the calibration system are reported.

Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment

“…The disappearance signal is most pronounced at the first oscillation minimum of P sur . Based on existing accelerator and atmospheric ν μ measurements of Δm 2 32 , this corresponded to a distance L f ≈ 1.6 km for reactorν e with a mean energy of ∼4 MeV. Significantν e disappearance in the near detectors would have reduced the overall sensitivity of the far-to-near comparison, so L n was kept to ∼500 m or less.…”

“…Three automated calibration units (ACUs) were used to deploy radioactive sources ( 60 Co, 68 Ge, and 241 Am-13 C) and light-emitting diodes (LEDs) through narrow teflon-bellow penetrations into the GdLS and LS regions. Details of the calibration system are provided in [32].…”

“…The details of the calibration process are discussed in this section. Descriptions of the calibration systems are given in [32] and [33].…”

New Measurement of Antineutrino Oscillation with the Full Detector Configuration at Daya Bay

“…Data taking was paused on 28 July 2012 while two new ADs were installed, one in EH2 and the other in EH3. During the installation, a broad set of calibration sources were deployed into the two ADs of EH1 using automated calibration units [12] and a manual calibration system [13]. Operation of the full experiment with all eight ADs started on 19 October 2012.…”

Improved Search for a Light Sterile Neutrino with the Full Configuration of the Daya Bay Experiment

“…A total of 192 photomultiplier tubes are installed on the vertical surfaces, and the top and bottom surfaces are covered with optical reflectors. Three automated calibration units [27] that store and deploy calibration sources and Light Emitting Diodes sit on top of the stainless steel vessel. The ADs are housed inside a muon veto system consisting of two optically separated inner and outer water pools [28] that provide shielding from ambient radiation and serve as active water Cherenkov muon detectors.…”