Characterization and optimization of p-Terphenyl (pTP) wavelength shifting coatings for photon detection systems in liquid argon neutrino detectors

A major technical challenge in DUNE is the efficient detection of scintillation light from liquid argon at 127 nm. Currently, para-Terphenyl (pTP) is used on detector materials to wavelength-shift the scintillation light into the sensitivity range of conventional photodetectors (~420nm). But coating surfaces manually with pTP is time-consuming and has limited uniformity and reproducibility. In this study, we investigate the viability of using industrial vacuum vapor deposition by commercial vendors to produce uniform and scalable pTP coatings with improved quality control. Coating samples produced in collaboration with LaserFiberOptics LLC were characterized using a UV monochromator to evaluate emission spectra and wavelength shifting efficiency. Coating thicknesses were measured with a profilometer to assess layer uniformity and correlation with optical performance. Preliminary results indicate promising consistency in emission peak profiles and improved spatial uniformity compared to manual coatings. This work contributes to the development of scalable and efficient photon detection systems for LAr-based detectors.