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This study presents calibration methods for Silicon Photomultipliers (SiPMs) used in the JUNO-TAO detector, a satellite observatory designed to measure antineutrino energy spectra from a nuclear reactor with unprecedented precision (better than 2% energy resolution at 1 MeV). The researchers developed channel-level and tile-level calibration techniques for key SiPM parameters including dark count rate, photon detection efficiency, gain, timing offset, and optical crosstalk, achieving calibration biases below 4% across all parameters. Simulation studies with one million events demonstrated that these calibration accuracies result in minimal degradation of the detector's vertex precision and energy resolution (below 2% and 3% respectively).
Why it matters
Precise measurement of reactor antineutrino spectra is crucial for fundamental neutrino physics research and nuclear reactor monitoring. The validated calibration methods ensure the JUNO-TAO detector can achieve its design goals, potentially enabling more accurate studies of neutrino oscillations and neutrino mass hierarchy, while also advancing SiPM calibration techniques applicable to other low-light detection experiments.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Abstract: The Taishan Antineutrino Observatory (TAO or JUNO-TAO) is a satellite observatory for the Jiangmen Underground Neutrino Observatory (JUNO), located 44 meters away from the No.1 reactor of the Taishan Nuclear Power Plant. TAO can measure the reactor antineutrino energy spectrum with excellent energy resolution (better than 2% at 1 MeV) using state-of-the-art Silicon Photomultipliers (SiPMs) operated at low temperature. To achieve this goal, the SiPMs (together with their readout electronics) must be well calibrated. This paper presents the channel-level calibration methods for the dark count rate (DCR), relative photon detection efficiency (PDE), time offset, gain, and internal optical crosstalk (IOCT) of the SiPMs based on charge and time information of the collected events. For the tile-level calibration of the external optical crosstalk (EOCT), in terms of its rate and emission angle distribution, a novel method is proposed by switching on and off different groups of SiPMs with an LED placed in the detector. Using one million simulated events, the expected calibration biases are evaluated for all the aforementioned parameters: relative PDE (~3%), IOCT (1.4%), DCR (0.4%), EOCT Rate (<0.1%), gain (<0.1%), time offset (<0.2 ns). The emission angle distribution of the EOCT photons could be measured with a bias of less than 4% in the main angular range. With the this calibration accuracy, the overall impacts of SiPM parameter uncertainties and calibration biases on vertex precision and energy resolution are limited, with relative degradation below 2% and 3%, respectively. It verifies the validity of the calibration method for the JUNO-TAO detector.
Source: Calibration Methods of Silicon Photomultiplier for JUNO-TAO Central Detector