Measurements of Angle-Resolved Reflectivity of PTFE in Liquid Xenon with IBEX

TL;DR

This study measures how PTFE reflects xenon scintillation light at various angles in liquid xenon, revealing high reflectivity and the dominance of specular reflection, which is crucial for optimizing particle detector performance.

Contribution

It provides the first detailed angular reflectivity measurements of PTFE in liquid xenon, modeled with few parameters, and explores effects of material and environmental factors.

Findings

Reflectivity near 100% at high angles of incidence.

Dominance of specular over diffuse reflection due to total internal reflection.

Dependence of reflectivity on PTFE type, surface finish, and xenon pressure.

Abstract

Liquid xenon particle detectors rely on excellent light collection efficiency for their performance. This depends on the high reflectivity of polytetrafluoroethylene (PTFE) at the xenon scintillation wavelength of 178 nm, but the angular dependence of this reflectivity is not well-understood. IBEX is designed to directly measure the angular distribution of xenon scintillation light reflected off PTFE in liquid xenon. These measurements are fully described by a microphysical reflectivity model with few free parameters. Dependence on PTFE type, surface finish, xenon pressure, and wavelength of incident light is explored. Total internal reflection is observed, which results in the dominance of specular over diffuse reflection and a reflectivity near 100% for high angles of incidence.