Reflection of the xenon scintillation light from Polytetrafluoroethylene (PTFE)

Liquid Xenon particle detectors are being used for a number of applications including dark matter search and neutrino-less double beta decay experiments. Polytetrafluoroethylene (PTFE) is often used in these detectors both as an electrical insulator and as a light reflector to improve efficiency of detection of scintillation photons. However, liquid xenon emits in the VUV wavelength region (λ=175 nm) where the properties of PTFE are not sufficiently known. In this work we report on measurements of PTFE reflectance, including its angular distribution, for the xenon scintillation light. Various samples of PTFE, manufactured by different processes (extruded, expanded, skived and pressed) have been studied. The data were interpreted with a physical model comprising both specular and diffuse reflections. The reflectance obtained for these samples, except the expanded sample, is between 0.47 and 0.66 at θi=0°. Some other fluoropolymers namely ETFE, FEP and PFA were also measured.