The reflectivity increases with angle of incidence for all samples but one.
The reflectivity is determined to 25–36% at an angle of incidence of 20° for the four samples investigated in this work. A dedicated setup at the University of Münster has been used that allows to acquire angular reflection spectra of various samples immersed in liquid xenon with 0.45° resolution. This work presents extensive reflectivity studies with Silicon Photomultipliers and other samples in liquid xenon at vacuum ultraviolet wavelengths. The detector needs to be designed thoroughly to maximise the light yield and the optical behaviour of the Silicon Photomultipliers in the detector medium plays a key part in detector simulations. The energy resolution for any particle interaction that occur in the detector is a crucial parameter of such experiments and depends on the capability of the detector to collect as much scintillation light from the events as possible. Silicon Photomultipliers are pixelated semiconductor photosensors with single photon resolution and are regarded as very promising technology to construct next-generation, cutting-edge detectors for low-background experiments in astroparticle physics. We then use simulations to project the precision with which such a source could calibrate spatial corrections to the light and charge response of the nEXO TPC. In this work we describe a process for producing the source and preliminary experimental tests. The 36.3 day half-life of ¹²⁷ Xe and its small Q-value compared to that of ¹³⁶ Xe 0 νββ would allow a small activity to be maintained continuously in the detector during normal operations without introducing additional backgrounds, thereby enabling in-situ calibration and monitoring of the detector response. To optimize the event reconstruction and energy resolution, calibrations are needed to map the position- and time-dependent detector response. The xenon, used both as source and detection medium, will be enriched to 90% in ¹³⁶ Xe. nEXO is a next-generation search for neutrinoless double beta decay (0 νββ ) that will use a 5-tonne, monolithic liquid xenon time projection chamber (TPC). We study a possible calibration technique for the nEXO experiment using a ¹²⁷ Xe electron capture source.
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