Measurement of Optical Properties of Tetraphenyl Butadiene

Liquid argon is a popular detection medium for both neutrino and dark matter experiments, due to the high light yield and potential for high-precision pulse shape discrimination. A wavelength shifter, such as tetraphenyl butadiene (TPB), is required in order to detect the extreme UV photons produced in particle interactions. This poster presents updates on ongoing work to characterize the microphysical optical properties of TPB. By shining UV light on thin-film TPB samples of varying thickness, both in vacuum and submerged in liquid argon, and then looking at the angular reemission distribution using a PMT, we can measure properties of the TPB, such as UV absorption length and photon reemission quantum efficiency. We have constructed a detailed, high-precision Monte Carlo model of our apparatus. A mirror is used to calibrate the Monte Carlo simulation, as well as discern to which systematic effects our experiment is most sensitive. By comparing the Monte Carlo simulation with data, this study will yield refined measurements of the microphysical properties of TPB, allowing for more control and confidence in any model of this material for next-generation detector design. This poster will present the most recent results from this work, including model predictions and vacuum data.