ARAPUCA, light trapping device for the DUNE experiment

Abstract

The Deep Underground Neutrino Experiment (DUNE) will be the first mega-science program on the US soil and will shade light on some of the open questions in neutrino physics. The experiment foresees the realization of an intense neutrino beam at Fermilab (Chicago - USA), of a near detector to monitor the beam and a far detector installed in the Sanford Underground Research Facility (SURF), 1300 km far away. Four 10 kt Liquid Argon Time Projection Chambers (LArTPC) will compose the 40 kt far detector modules to perform the precise measurements required for DUNE. The experimental technique uses charge and light signal from ionizing radiations in liquid argon to fully reconstruct neutrino interactions with excellent spatial resolution, calorimetric measurements and particle identification. The liquid argon scintillation light is produced around 127 nm within a few nanoseconds from the radiation passage. Its detection may improve the LArTPC calorimetric besides giving the time stamp of non-beam events, which is vital in fiducializing nucleon-decay events. The DUNE Photon Detection System (PDS) is responsible to efficiently collect this light in order to fiducialize the active volume of the detector with $>99\%$ efficiency. The PDS will be composed by 1,500 X-ARAPUCA modules, a light trapping device that was the main subject of this thesis. In this work, the research and development of the ARAPUCA devices will be presented. The full characterization of the prototypes were performed in dedicated liquid argon tests, in Brazil and Italy, where comparable efficiencies of (2.2 $\pm$ 0.4)% and (1.9 $\pm$ 0.1)% were found. A new wavelength shifter developed in Italy in collaboration with the Universita degli Studi di Milano-Bicocca will be presented. It allowed to increase the light detection efficiency of about 50% and resulted in an overall efficiency of (2.9 $\pm$ 0.1)% of the X-ARAPUCA.