Measuring Optical Properties in Liquid Xenon with LIXO2

Liquid xenon (LXe) is widely used in various neutrino and dark matter experiments, including the next-generation searches for dark matter and neutrinoless double beta decay, DARWIN and nEXO. LXe scintillates in vacuum ultraviolet (VUV) region, and understanding reflectance and transmittance of materials and photodetection efficiency (PDE) of photosensors in this region is important for optimizing energy resolution and sensitivity of these experiments. LIXO is a setup dedicated to such measurements that was constructed at the University of Alabama. It has already provided the first measurement of angular-resolved reflectivity and PDE of a SiPM in LXe. Recently, LIXO has been upgraded to improve measurement speed, reduce uncertainties, and allow transparency measurements in LXe. This talk will report on the design and characterization of the upgraded system, LIXO2, and will present first results on reflectivity measurements of materials relevant for the next-generation rare event searches in liquid xenon.