Measurements of the intrinsic quantum efficiency and absorption length of tetraphenyl butadiene thin films in the vacuum ultraviolet regime

TL;DR

This paper reports the first measurements of the intrinsic quantum efficiency and absorption length of TPB thin films in the vacuum ultraviolet range, crucial for optimizing liquid noble gas detectors in particle physics.

Contribution

It provides the first room-temperature microphysical quantum efficiency measurements of vacuum-deposited TPB films, independent of optical effects, along with absorption length and re-emission efficiency data.

Findings

Measured quantum efficiency of TPB films in VUV regime

Determined absorption length of TPB in VUV range

Enhanced understanding of TPB optical properties for detector design

Abstract

A key enabling technology for many liquid noble gas (LNG) detectors is the use of the common wavelength shifting medium tetraphenyl butadiene (TPB). TPB thin films are used to shift ultraviolet scintillation light into the visible spectrum for detection and event reconstruction. Understanding the wavelength shifting efficiency and optical properties of these films are critical aspects in detector performance and modeling and hence in the ultimate physics sensitivity of such experiments. This article presents the first measurements of the room-temperature microphysical quantum efficiency for vacuum-deposited TPB thin films - a result that is independent of the optics of the TPB or substrate. Also presented are measurements of the absorption length in the vacuum ultraviolet regime, the secondary re-emission efficiency, and more precise results for the "black-box" efficiency across a broader spectrum of wavelengths than previous results. The low-wavelength sensitivity, in particular, would allow construction of LNG scintillator detectors with lighter elements (Ne, He) to target light mass WIMPs.