Ageing studies of TPB in noble gas detectors for dark matter and neutrinoless ββ decay searches

Abstract

Noble gases (Xe, Ar, Kr) are very attractive as detector media in Dark Matter search and neutrinoless double-beta decay experiments. However, the detection of their scintillation light (in the VUV spectral region) requires shifting the VUV light to visible light, where standard photosensors are more efficient. Tetraphenyl butadiene (TPB) is widely used as wavelength shifter, absorbing the VUV light and re-emitting in the blue region (~430 nm). TPB is an organic molecule that may degrade due to exposure to environmental agents and also to ultraviolet light. In this work, we present TPB ageing studies due to exposure to VUV light, aiming at quantifying the reduction of the absolute fluorescence yield of TPB coatings of several thicknesses (130 nm, 260 nm, 390 nm, 1600 nm), exposed to various doses of VUV light at 170 nm (similar to the Xe scintillation). In our setup, the VUV light is produced from a vacuum monochromator coupled to a deuterium lamp. The VUV exposure in our setup is compared to the exposure obtained in the electroluminescent gaseous Xe TPC of the NEXT-100 experiment for neutrinoless double-beta decay search.

Wavelength Shifters for Applications in Liquid Argon Detectors

“…Yahlali et al [98] demonstrated, however, that the conversion efficiency loss after exposure to VUV light comparable with that integrated over a ∼5 year lifetime of a typical experiment does not exceed 15%, which is consistent with the results of, e.g., GERDA, DEAP-1, DEAP-3600 or DarkSide-50. Furthermore, a thick TPB coating (1.6 µm) had stronger resistance to VUV radiation damage than a thin coating (130 nm).…”

Wavelength shifters for applications in liquid argon detectors

“…Yahlali et al [96] demonstrated, however, that the conversion efficiency loss after exposure to VUV light comparable with that integrated over a ∼5 year lifetime of a typical experiment does not to exceed 15%, which is consistent with the results of e.g. GERDA, DEAP-1, DEAP-3600 or DarkSide-50.…”

SiPM Readout Technique in a High Pressure Xenon Electroluminescent TPC for neutrinoless $\beta\beta$-decay

“…The conversion efficiency of vacuum-evaporated TPB-coatings as a function of thickness and their ageing effects when exposed to VUV light at the xenon scintillation wavelength is reported in ref. [7]. The tracking plane of NEW is instrumented with about 1800 SiPMs SensL MicroFC-10035-SMT-GP, arranged in 28 Kapton boards (KB) as shown in figure 2-right, temperature sensors (NTC) and one LED for calibration.…”