N. Yahlali, L. M. P. Fernandes, K. González, A. N. C. Garcia, A. Soriano
Silicon photomultipliers (SiPMs) are photosensors widely used for imaging in a variety of high energy and nuclear physics experiments. In noble-gas detectors for double-beta decay and dark matter experiments, SiPMs are attractive photosensors for imaging but they are insensitive to the VUV scintillation emitted by the noble gases (xenon and argon). This difficulty is overcome in the NEXT experiment by coating the SiPMs with tetraphenyl butadiene (TPB) to convert the VUV light into visible light. TPB requires stringent storage and operational conditions to prevent its degradation by environmental agents. The development of UV sensitive SiPMs is thus of utmost interest for experiments using UV light and for noble-gas detectors. It is in particular an important issue for a robust and background free neutrinoless double-beta decay experiment with xenon gas aimed by NEXT. The photon detection efficiency (PDE) of UV-enhanced SiPMs without protective window and with silicon resin window provided by Hamamatsu was determined for light in the range 250-500 nm. The PDE of standard SiPMs of the same model (S10362-33-50C) coated and non-coated with TPB was also determined for comparison. In the UV range between 250 nm and 350 nm, the PDE of the standard SiPM is shown to decrease strongly, down to about 3%. The UV-enhanced SiPM without window is shown to have the maximum PDE close to 44% at 325 nm and to 30% at 250 nm. The PDE of the UV-enhanced SiPM with silicon resin window has a similar trend in the UV range, although it is significantly lower. The TPB-coated SiPM has shown to have about 6 times higher PDE than the non-coated SiPM in the range 250-315 nm. This is however below the performance of the UV-enhanced prototypes in the same wavelength range. Imaging in noble-gas detectors using UV-enhanced SiPMs is discussed.
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http://arxiv.org/abs/1210.4746
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