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VUV Reflectance Measurements for Materials Relevant to Argon and Xenon Experiments

J. Soto-Oton, H. Amar, A. Cervera, A. Roche

TL;DR

The study addresses the lack of reliable VUV reflectance data for detector materials used in noble-gas experiments by developing an angular-resolved reflectance system in gaseous argon. It measures aluminum and stainless steel in UV–VIS and VUV, using a Phong-like shading-function model to describe angular distributions and reports low VUV reflectance (~10–15% at 45° AOI) compared with UV–VIS values, with significant implications for light-yield simulations. The approach provides realistic, angle-resolved material characterizations that can improve photon transport modeling and detector designs for next-generation experiments. The work also demonstrates the feasibility of VUV optical characterization in a GAr environment, offering a flexible platform for systematic material studies and future extensions to additional materials and conditions.

Abstract

Accurate knowledge of material reflectance in the vacuum ultraviolet (VUV) range is crucial for optimizing photon detection in noble gas detectors such as DUNE. Despite its importance, reflectance values for detector materials in the VUV region remain poorly characterized, with literature values showing significant variation depending on surface termination and finish. We present an angular-resolved reflectance measurement system developed at IFIC that operates in a gaseous argon atmosphere, enabling realistic measurements of detector materials under controlled conditions. The setup couples a deuterium lamp to a monochromator and employs a motorized PMT rotating around the sample to measure reflected light distributions across a wide angular range. We have characterized two key DUNE materials -- aluminum field cage profiles and stainless steel cryostat membranes -- in both the UV-VIS (300-500 nm) and VUV (128-200 nm) ranges. In the UV-VIS region, we confirm literature values of approximately 60% reflectance for aluminum and 40% for stainless steel. Preliminary VUV measurements at 45° angle of incidence yield reflectance values of 10-15% for both materials, significantly lower than their UV-VIS counterparts. The reflected light distributions exhibit a mixed character between specular and diffuse reflection. These results have direct implications for detector simulations and light yield predictions in next-generation experiments.

VUV Reflectance Measurements for Materials Relevant to Argon and Xenon Experiments

TL;DR

The study addresses the lack of reliable VUV reflectance data for detector materials used in noble-gas experiments by developing an angular-resolved reflectance system in gaseous argon. It measures aluminum and stainless steel in UV–VIS and VUV, using a Phong-like shading-function model to describe angular distributions and reports low VUV reflectance (~10–15% at 45° AOI) compared with UV–VIS values, with significant implications for light-yield simulations. The approach provides realistic, angle-resolved material characterizations that can improve photon transport modeling and detector designs for next-generation experiments. The work also demonstrates the feasibility of VUV optical characterization in a GAr environment, offering a flexible platform for systematic material studies and future extensions to additional materials and conditions.

Abstract

Accurate knowledge of material reflectance in the vacuum ultraviolet (VUV) range is crucial for optimizing photon detection in noble gas detectors such as DUNE. Despite its importance, reflectance values for detector materials in the VUV region remain poorly characterized, with literature values showing significant variation depending on surface termination and finish. We present an angular-resolved reflectance measurement system developed at IFIC that operates in a gaseous argon atmosphere, enabling realistic measurements of detector materials under controlled conditions. The setup couples a deuterium lamp to a monochromator and employs a motorized PMT rotating around the sample to measure reflected light distributions across a wide angular range. We have characterized two key DUNE materials -- aluminum field cage profiles and stainless steel cryostat membranes -- in both the UV-VIS (300-500 nm) and VUV (128-200 nm) ranges. In the UV-VIS region, we confirm literature values of approximately 60% reflectance for aluminum and 40% for stainless steel. Preliminary VUV measurements at 45° angle of incidence yield reflectance values of 10-15% for both materials, significantly lower than their UV-VIS counterparts. The reflected light distributions exhibit a mixed character between specular and diffuse reflection. These results have direct implications for detector simulations and light yield predictions in next-generation experiments.
Paper Structure (9 sections, 1 equation, 4 figures)

This paper contains 9 sections, 1 equation, 4 figures.

Table of Contents

  1. Introduction
  2. Experimental setup
  3. Methodology
  4. Results
  5. UV-VIS Measurements (300–500 nm)
  6. VUV Measurements (128–200 nm) in GAr
  7. Integrated reflectance
  8. Discussion
  9. Conclusions and future steps

Figures (4)

  • Figure 1: A picture of the measurement setup inside the black box is shown on the left, while a diagram of the setup on the right.
  • Figure 2: Left: Angular-resolved reflectance intensity for the stainless-steel sample at an angle of incidence of 45º and a wavelength of 300 nm. Right: Reflectance of the SS and Al samples.
  • Figure 3: Angular-resolved reflected intensity of the SS and Al samples at VUV wavelengths.
  • Figure 4: Reflectance of the SS and Al samples in the VUV and UV/Visisble range.