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Optimization of the X-Arapuca Photon Collection Efficiency for the DUNE Horizontal Drift Far Detector

E. Bertolini, C. Brizzolari, F. Bruni, P. Carniti, C. M. Cattadori, S. Copello, E. Cristaldo, M. Delgado, F. Galizzi, C. Gotti, D. Guffanti, A. A. Machado, L. Malinverni, L. Meazza, F. Meinardi, G. Pessina, G. Raselli, M. Rossella, E. Segreto, H. Souza, F. Terranova, D. Warner

TL;DR

This study investigates how to boost the photon-collection efficiency of the DUNE FD-HD X-Arapuca module. By combining targeted laboratory measurements with Geant4 optical simulations, it identifies the key loss mechanisms and evaluates multiple design modifications, including improved WLS-LG sealing, two-piece light guides with optimized cuts, and selective use of dichroic filters. The results show potential PDE gains up to ~84% over the baseline, primarily driven by better optical sealing and edge extraction, with nuanced trade-offs for the entrance-window dichroic coatings. The findings provide practical, near-term strategies to enhance the DUNE PDS performance and inform future X-Arapuca implementations.

Abstract

The Deep Underground Neutrino Experiment (DUNE) Far Detector (FD) Photon Detection System (PDS) employs the X-Arapuca concept, a photon trapping system relying on reflective surfaces and dichroic filters. In this paper are reported measurements, performed at the University of Milano-Bicocca, aimed at increasing the FD Horizontal Drift (HD) PDS module efficiency. The baseline implementation of the X-Arapuca concept for the FD-HD PDS module is close to the DUNE requirements as demonstrated in the collaborations laboratory testing. However, an increased performance would provide a safety margin for a detector planned to be operated for 30 years, without possibility of performing maintenance. A higher detector performance would also benefit the DUNE low energy physics program. The already proven Milano-Bicocca setup has been utilized to test different PDS module configurations comparing them to the original baseline. Exploiting prior knowledge of the X-Arapuca components and Geant4 based optical simulations it has been possible to achieve up to an ~84% performance increase over the baseline design. In the following it is presented the testing procedure, the performed measurements and a brief discussion on the obtained results.

Optimization of the X-Arapuca Photon Collection Efficiency for the DUNE Horizontal Drift Far Detector

TL;DR

This study investigates how to boost the photon-collection efficiency of the DUNE FD-HD X-Arapuca module. By combining targeted laboratory measurements with Geant4 optical simulations, it identifies the key loss mechanisms and evaluates multiple design modifications, including improved WLS-LG sealing, two-piece light guides with optimized cuts, and selective use of dichroic filters. The results show potential PDE gains up to ~84% over the baseline, primarily driven by better optical sealing and edge extraction, with nuanced trade-offs for the entrance-window dichroic coatings. The findings provide practical, near-term strategies to enhance the DUNE PDS performance and inform future X-Arapuca implementations.

Abstract

The Deep Underground Neutrino Experiment (DUNE) Far Detector (FD) Photon Detection System (PDS) employs the X-Arapuca concept, a photon trapping system relying on reflective surfaces and dichroic filters. In this paper are reported measurements, performed at the University of Milano-Bicocca, aimed at increasing the FD Horizontal Drift (HD) PDS module efficiency. The baseline implementation of the X-Arapuca concept for the FD-HD PDS module is close to the DUNE requirements as demonstrated in the collaborations laboratory testing. However, an increased performance would provide a safety margin for a detector planned to be operated for 30 years, without possibility of performing maintenance. A higher detector performance would also benefit the DUNE low energy physics program. The already proven Milano-Bicocca setup has been utilized to test different PDS module configurations comparing them to the original baseline. Exploiting prior knowledge of the X-Arapuca components and Geant4 based optical simulations it has been possible to achieve up to an ~84% performance increase over the baseline design. In the following it is presented the testing procedure, the performed measurements and a brief discussion on the obtained results.

Paper Structure

This paper contains 19 sections, 7 equations, 20 figures, 3 tables.

Table of Contents

  1. Introduction
  2. The X-Arapuca
  3. The entrance window
  4. Assessment of the entrance window transparency
  5. The Liquid Argon test bench
  6. Setup
  7. SiPMs and Electronics
  8. Data acquisition, analysis and simulation
  9. Calibration
  10. Muon analysis
  11. Alpha analysis
  12. Photon Detection Efficiency
  13. Geant4 based optical simulation
  14. Measurements and results
  15. WLS-LG with dimpled edges
  16. ...and 4 more sections

Figures (20)

  • Figure 1: The X-Arapuca operating principle Guffanti.
  • Figure 2: ZAOT DF Transmission curves measured in water ($n_{H2O}=1.33$)Cattadori_2024. The two PL spectra of the pTP (red) and of the secondary WLS chromophore (gray) embedded in the PMMA are also reported
  • Figure 3: A schematic representation of the vacuum setup used to evaluate, at room temperature, the conversion and transmission efficiency of different window samples.
  • Figure 4: CAD model of the XA-HD module channel inside the setup vacuum vessel and picture of the channel mounted on the vessel flange.
  • Figure 5: On the left, optical fiber feed through at the top of the chamber. On the right, optical fiber end fixed to the support next to the alpha source rail.
  • ...and 15 more figures