Production and propagation of the scintillation light in LAr-TPCs: from prototypes to bigger detectors

by Chiara Filomena Lastoria


Because of its properties, liquid argon (LAr) is a conventional medium for neutrinos and dark matter detectors such that its operation in time projection chamber (TPC) detectors became quite common. Nevertheless, proving the scalability of these detectors toward their operation at giant scales is critical.

In the field of long-baseline neutrino oscillation experiments, DUNE (Deep Underground Neutrino Experiment) is the current leading-edge project; in the far detector, it envisages four 10-kton LAr-TPCs, in different configurations, but none of them ever used such a large LAr mass. Among those, a LAr-TPC based on the so-called dual-phase (DP) technology has been considered because particularly advantageous for covering longer drift paths. In order to validate the suitability of this technology for DUNE, two prototypes with an increasing LAr active volume have been operated at CERN: the WA105-DP demonstrator, of 3x1x1 m3 (~4.2 tons), and ProtoDUNE-DP, of 6x6x6 m3 (~300 tons). At the time of its operation, the WA105-DP detector was the first prototype ever worked at the ton scale, allowing the achievement of important technological milestones. In the DP LAr-TPCs, the photon detection system (PDS) is typically used for triggering but it is expected to be valuable for discriminating non-beam or low-energy events.

In this talk, the analysis of the light signal data collected during the whole WA105-DP prototype operation is discussed. The complete characterization of the two light signals produced in liquid and gas phases allowed the achievement of pioneering results deepening the understanding of the LAr micro-physics. Consequently, the knowledge of the light production and its subsequent propagation in the LAr bulk has been enhanced, improving the light simulation for physics sensitivity studies in big LAr detectors.