Demonstration of a novel modular neutrino detector

The Deep Underground Neutrino Experiment (DUNE) is designed to perform precision measurements of neutrino oscillations by combining a high-intensity, broad-spectrum neutrino beam with large-mass, highly granular detectors. A critical requirement for achieving this goal is the accurate characterisation of the unoscillated neutrino beam at a near detector site, located close to the beam source, before the neutrinos propagate over a distance of 1500m to a far detector complex, where the oscillated beam is measured. The near site will be instrumented with a modular detector based on liquid argon time projection chamber (LArTPC) technology. The modular design of this detector has proven advantageous for operation in the high-rate environment of the intense neutrino flux at the DUNE near detector. In this thesis, it is shown how the optical segmentation imposed by the detector modularity enhances the ability to localise scintillation light and facilitates efficient matching between the light and charge signals produced by neutrino interactions, an essential capability for disentangling overlapping events within a single beam spill. To demonstrate and validate the modular approach, the 2x2 Demonstrator, which consists of four fully instrumented LArTPC modules, was developed as part of this thesis. The detector was operated in the Neutrinos at the Main Injector (NuMI) beam at the Fermi National Accelerator Laboratory and successfully integrated light and charge detection, cryogenic infrastructure, timing systems, and data acquisition under realistic beam conditions. As part of this work, a comprehensive light readout system was developed and implemented as a core component of the 2×2 Demonstrator, including the design and production of light detectors, the establishment of quality control procedures, the integration of an in-situ calibration system, and the implementation of a fully integrated run control. Performance measurements of the 2x2 Demonstrator show a photon detection efficiency of (0.19 ± 0.02) % and (0.63 ± 0.13) % for the deployed ArCLight and LCM light detection modules, respectively. Using timing information extracted from scintillation light data, the substructure of the NuMI beam spills was resolved and an interaction timing resolution of less than 4 ns was demonstrated.

2025

dissertation

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