The ProtoDUNE Photon Detection System: technology validation and performance

Abstract DUNE is a long-baseline accelerator experiment currently in construction at Fermilab and SURF (South Dakota). The science objectives of DUNE include the search for CP violation in the leptonic sector and the identification of the neutrino mass hierarchy, along with the observation of supernova neutrino bursts and proton decay. The Far Detector consists of four modules located deep underground, three of those instrumented with Liquid Argon TPCs and equipped with the DUNE Photon Detection System (PDS). The PDS is based on a novel light trapping technology that greatly enhances the DUNE physics reach, improving vertex identification, energy resolution and providing the trigger for non-beam events. Following a first run of data taking (from 2018 to 2020), the PDS of the two prototypes of the Far Detector located at CERN Neutrino Platform, ProtoDUNE-HD and ProtoDUNE-VD, is currently being reinstalled in order to implement the final design of the first (Horizontal Drift) and second (Vertical Drift) module. This paper presents the latest results of the PDS from test facilities and the status of the installation in ProtoDUNE in view of its second run. The most important achievements of the Vertical Drift PDS are reported, with emphasis on the new SiPM configuration and cold electronics, the custom WaveLength Shifting bars, and the latest generation of the dichroic filter designed for ProtoDUNE-VD.