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Modeling Light Signals Using Data from the First Pulsed Neutron Source Program at the DUNE Vertical Drift ColdBox Test Facility at CERN Neutrino Platform

A. Paudel, W. Shi, P. Sala, F. Cavanna, W. Johnson, J. Wang, W. Ketchum, F. Resnati, A. Heindel, A. Ashkenazi, E. Bertholet, E. Bertolini, D. A. Martinez Caicedo, E. Calvo, A. Canto, S. Manthey Corchado, C. Cuesta, Z. Djurcic, M. Fani, A. Feld, S. Fogarty, F. Galizzi, S. Gollapinni, Y. Kermaïdic, A. Kish, F. Marinho, D. Torres Muñoz, A. Verdugo de Osa, L. Paulucci, W. Pellico, V. Popov, J. Rodriguez Rondon, D. Leon Silverio, S. Sacerdoti, H. Souza, R. C Svoboda, D. Totani, V. Trabattoni, L. Zambelli

TL;DR

This work tests light signals produced by a pulsed neutron source in a small vertical-drift LArTPC using Fluka-based simulations to model detector geometry, neutron interactions, and photon transport. The data-MC comparison shows good agreement in the detected photoelectrons (up to ~650 PE per XA) and a consistent light-decay time constant between data and simulation, validating the approach for MeV-scale calibration. The study develops robust calibration and data-selection pipelines (ADC-to-PE, relative PDE, and MC photon-to-peak conversions) and identifies systematic effects—most notably the electric field in the non-readout LAr region—that will inform future prototype runs at larger detectors and enable neutron-capture tagging for improved energy calibration and background rejection in DUNE.

Abstract

In this paper, we present a first quantitative test of detected light signals produced in a pulsed neutron source run in a small vertical drift LArTPC at the CERN neutrino platform ColdBox test facility. The ColdBox cryostat, detectors, neutron sources, and particle interactions are modeled and simulated using Fluka. A good agreement is found in the detected number of photoelectrons, with values below 650 photoelectrons in both data and simulation, for all four X-ARAPUCA photodetectors on the cathode in the LArTPC. A time constant is also fitted from the neutron-beam-off light signal spectrum and found consistent between data and MC. Several important systematic effects are discussed and serve as guides for future runs at larger LArTPCs.

Modeling Light Signals Using Data from the First Pulsed Neutron Source Program at the DUNE Vertical Drift ColdBox Test Facility at CERN Neutrino Platform

TL;DR

This work tests light signals produced by a pulsed neutron source in a small vertical-drift LArTPC using Fluka-based simulations to model detector geometry, neutron interactions, and photon transport. The data-MC comparison shows good agreement in the detected photoelectrons (up to ~650 PE per XA) and a consistent light-decay time constant between data and simulation, validating the approach for MeV-scale calibration. The study develops robust calibration and data-selection pipelines (ADC-to-PE, relative PDE, and MC photon-to-peak conversions) and identifies systematic effects—most notably the electric field in the non-readout LAr region—that will inform future prototype runs at larger detectors and enable neutron-capture tagging for improved energy calibration and background rejection in DUNE.

Abstract

In this paper, we present a first quantitative test of detected light signals produced in a pulsed neutron source run in a small vertical drift LArTPC at the CERN neutrino platform ColdBox test facility. The ColdBox cryostat, detectors, neutron sources, and particle interactions are modeled and simulated using Fluka. A good agreement is found in the detected number of photoelectrons, with values below 650 photoelectrons in both data and simulation, for all four X-ARAPUCA photodetectors on the cathode in the LArTPC. A time constant is also fitted from the neutron-beam-off light signal spectrum and found consistent between data and MC. Several important systematic effects are discussed and serve as guides for future runs at larger LArTPCs.

Paper Structure

This paper contains 17 sections, 12 figures, 5 tables.

Table of Contents

  1. Motivation
  2. VD ColdBox Test Facility at CERN Neutrino Platform
  3. Pulsed Neutron Source
  4. Samples
  5. Data
  6. Monte Carlo
  7. Calibration and Data Selection
  8. ADC to Photoelectron Calibration in data
  9. Relative PDE Calibration in data
  10. Photon to Peak ADC Calibration in MC
  11. Data Selection
  12. Result
  13. Light Signal Amplitude
  14. Light Signal Time Constant
  15. Discussion on Excess at High PE in Data
  16. ...and 2 more sections

Figures (12)

  • Figure 1: ColdBox detector and PNS geometry in April 2024 run. Left: top view of the cold box. Four XA photon detectors, C1-C4, are instrumented on the cathode. Two XA photon detectors are installed on the membrane. Right: Deuterium-Deuterium neutron generator (bottom) and its shielding (top).
  • Figure 2: PNS burst mode set up in each 1-ms-long data-taking trigger window in the CB run in April 2024.
  • Figure 3: Side cross-sectional view (left) and top view (right) of the ColdBox and PNS geometry implemented in Fluka simulation.
  • Figure 4: Fluka simulated energy spectrum of $\gamma$ rays (top), from neutron captures in active LAr region of the ColdBox (top left), from neutron interactions in materials different from Ar (top right), and the total energy deposition distribution (bottom) in the ColdBox from processes in the active LAr and all other materials.
  • Figure 5: Comparison of light signals in Fluka simulation and PNS run data for all four XA modules on cathode. Top left: C1. Top right: C2. Bottom left: C3. Bottom right: C4.
  • ...and 7 more figures