Measurement of the absolute reflectance of polytetrafluoroethylene (PTFE) immersed in liquid xenon

TL;DR

This study measures the absolute reflectance of PTFE in liquid xenon, demonstrating high reflectance values that enhance light collection efficiency in LXe detectors, crucial for low-threshold particle detection.

Contribution

It provides the first experimental measurements of PTFE reflectance immersed in LXe, confirming high reflectance suitable for advanced scintillation detectors.

Findings

PTFE reflectance in LXe is ≥97%.

High reflectance enables lower energy detection thresholds.

Results support improved detector design for LXe-based experiments.

Abstract

The performance of a detector using liquid xenon (LXe) as a scintillator is strongly dependent on the collection efficiency for xenon scintillation light, which in turn is critically dependent on the reflectance of the surfaces that surround the active volume. To improve the light collection in such detectors the active volume is usually surrounded by polytetrafluoroethylene (PTFE) reflector panels, used due to its very high reflectance -- even at the short wavelength of scintillation light of LXe (peaked at $178\,\text{nm}$). In this work, which contributed to the overall R\&D effort towards the LUX-ZEPLIN (LZ) experiment, we present experimental results for the absolute reflectance of three different PTFE samples (including the material used in the LUX detector) immersed in LXe for its scintillation light. The obtained results show that very high bi-hemispherical reflectance values ($\geq97$%) can be achieved, enabling very low energy thresholds in liquid xenon scintillator-based detectors.