Speakers
Description
The X-Arapuca (XA) supercell is the basic unit of the Photon Detection System (PDS) of the Deep Underground Neutrino Experiment (DUNE). In total, 1,500 X-Arapuca with approximate dimensions of 210 x 12 cm$^2$ will be installed on the anode planes of the liquid argon time projection chamber (LArTPC). In the XA light trap device, the liquid argon scintillation light (with wavelength around 127 nm) is absorbed by a thin layer of para-Terphenyl (pTP) coated on a dichroic filter window which constitutes its acceptance window. PTP re-emits photons around 350 nm, above the filter cutoff. The light which enters the XA is downshifted again by the inner wavelength shifter plate (WLS plate) to a wavelength around 430 nm. The cut-off of the dichroic filter is placed at 400 nm: this allows the pTP shifted light to enter in the X-Arapuca and to trap the fraction of photons which escape from total internal reflection in the WLS plate. The light is collected by an array of silicon photo-sensors (SiPM) coupled at the edges of the WLS plate. In this work, we present the first characterization of the photon detection efficiency of an X-Arapuca prototype sizing 10 x 7.5 cm$^2$ in Brazil, where the X-Arapuca was exposed to alpha particles, cosmic muons and gammas in liquid argon. Operating the SiPMs at +5 and +5.5 V over the breakdown voltage, an efficiency ranging from 2.2% to 2.3% and from 2.7% to 3.1% was found, respectively.
