R &D of wavelength-shifting reflectors and characterization of the quantum efficiency of tetraphenyl butadiene and polyethylene naphthalate in liquid argon

Abstract Detectors based on liquid argon (LAr) often require surfaces that can shift vacuum ultraviolet (VUV) light and reflect the visible shifted light. For LAr instrumentation of LEGEND-200 neutrinoless double beta decay experiment, several square meters wavelength-shifting reflectors (WLSR) were prepared: reflector Tetratex® (TTX) was in-situ evaporated with wavelength shifter tetraphenyl butadiene (TPB). even larger detectors, TPB evaporation will be more challenging plastic films polyethylene naphthalate (PEN) are considered as an option to ease scalability. In this work, we first characterized absorption (and reflectivity) PEN, TTX) in response We then measured PEN coupled TTX a setup equipped VUV sensitive photomultiplier tube. The effective photon yield using absorbing reference sample, reflectivity quantified. characterization simulation along measurements modelling optical parameters TPB, allowed estimate absolute quantum efficiency (QE) (at 87K) for time: these found above 67 49%, respectively 90% CL). These results provide relevant input simulations experiments use LAr, such LEGEND-200, plan or scintillation