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Characterization of UV optical components for photon detector calibration in liquid argon TPCs

B. Behera, M. Bilal Azam, Z. Djurcic, A. Heindel, I. Helgeson, T. Hyden, D. Leon Silverio, S. Magill, D. A. Martinez Caicedo, M. Oberling, K. Pickner, A. Rafique, J. Rodríguez Rondon, D. Torres Muñoz, C. Winkers, L. Xia

Abstract

Large liquid argon time projection chambers (LArTPCs) require stable and well-characterized delivery of ultraviolet (UV) light for in situ calibration of photosensors at cryogenic temperatures. This article reports bench-top and cryogenic measurements of the optical components used in a UV light calibration system, including multi-mode fused-silica fibers, SMA-to-SMA connectors, optical fiber feedthroughs, and light-diffuser assemblies. Light loss in several fiber types and SMA connectors was measured across wavelengths from \qtyrange{275}{970}{nm}. In addition, light-loss measurements of the tested fibers after several liquid-nitrogen thermal cycles showed no statistically significant degradation relative to baseline measurements, and high-rate pulsed exposure (30-90 million pulses from a \qty{275}{nm} LED) likewise showed no measurable aging in jacketed fibers. A compact, palm-sized, 3D-printed PEEK diffuser housing with stacked UV-grade fused-silica diffusers yields Lambertian emission and the most uniform angular distribution. Optical components exhibiting improved UV transmission were deployed successfully in multiple DUNE small- and large-scale prototypes, demonstrating reliable operation of UV light calibration systems. These findings inform component selection and calibration procedures for achieving reliable, uniform UV light delivery in large-scale cryogenic detectors such as DUNE.

Characterization of UV optical components for photon detector calibration in liquid argon TPCs

Abstract

Large liquid argon time projection chambers (LArTPCs) require stable and well-characterized delivery of ultraviolet (UV) light for in situ calibration of photosensors at cryogenic temperatures. This article reports bench-top and cryogenic measurements of the optical components used in a UV light calibration system, including multi-mode fused-silica fibers, SMA-to-SMA connectors, optical fiber feedthroughs, and light-diffuser assemblies. Light loss in several fiber types and SMA connectors was measured across wavelengths from \qtyrange{275}{970}{nm}. In addition, light-loss measurements of the tested fibers after several liquid-nitrogen thermal cycles showed no statistically significant degradation relative to baseline measurements, and high-rate pulsed exposure (30-90 million pulses from a \qty{275}{nm} LED) likewise showed no measurable aging in jacketed fibers. A compact, palm-sized, 3D-printed PEEK diffuser housing with stacked UV-grade fused-silica diffusers yields Lambertian emission and the most uniform angular distribution. Optical components exhibiting improved UV transmission were deployed successfully in multiple DUNE small- and large-scale prototypes, demonstrating reliable operation of UV light calibration systems. These findings inform component selection and calibration procedures for achieving reliable, uniform UV light delivery in large-scale cryogenic detectors such as DUNE.
Paper Structure (14 sections, 6 equations, 28 figures, 15 tables)

This paper contains 14 sections, 6 equations, 28 figures, 15 tables.

Table of Contents

  1. Introduction
  2. Optical Fiber Properties
  3. Measurement of Light Transmission through Different Optical Fibers Types
  4. Optical Feedthrough and SMA-to-SMA Connector Interface Loss
  5. SMA-to-SMA Connector Attenuation Using Optical Power Measurements
  6. SMA-to-SMA Connector Attenuation Using Photodiode (PD) Response Measurements
  7. Measurement of the Light Loss through the Long Fibers
  8. Light Attenuation of Single 5.7 m Long FVP600660710 Fiber
  9. Light Attenuation of Single Long FP600URT Fiber
  10. Light Loss Measured through Combinations of Multiple FVP600660710 Fibers: DUNE-style Mockup
  11. Optical Fiber Thermal Cycling in Cryogenic Conditions
  12. Test of potential fiber degradation caused by a long UV-light exposure
  13. Light Diffuser Characterization
  14. Summary

Figures (28)

  • Figure 1: Cross-sectional drawing of optical fiber components, illustrating core, cladding and coating.
  • Figure 2: Comparison of light propagation in single-mode (left) and multi-mode (right) optical fibers with step-index profiles.
  • Figure 3: Left: Successful fiber termination with intact core, cladding, and coating. Right: Fiber damaged during cleaving, showing visible damage in core and cladding.
  • Figure 4: Pictures with its respective diagram of the experimental setup used to measure fiber transparency. Left: Reference configuration, where the LED directly couples into the reference fiber connected to the power sensor. Right: Tested fiber configuration, where one end of the reference fiber is connected to the tested fiber using an SMA-to-SMA connector, and the other end of the tested fiber output at the far end is measured. In both cases, the LED is driven by a regulated 5 V power supply through the resistor-limited circuit visible on the breadboard.
  • Figure 5: Left: Transparency at four wavelengths (370 nm, 465 nm, 810 nm, and 970 nm) for each bare fiber type. Right: Transparency of each bare fiber type as a function of wavelength. Error bars represent the statistical uncertainty associated with each measurement.
  • ...and 23 more figures