HEP - ASTRO SEMINAR | Developing a Water Cherenkov Optical Time-Projection Chamber for Neutrino Detection

The LAPPD collaboration was formed to develop large-area photodetectors based on micro-channel plates (MCP) for precisetime-of-flight measurements in large-scale detectors for high-energy physics. As part of this project, we have designed readout electronics for these 400 cm^2 photodetectors using a custom front-end 10 gigasample-per-second waveform-digitizing integrated circuit. The prospect of large-area, scalable, and high-granularity photodetectors opens the possibility of building a water-based optical time-projection chamber (OTPC), in which high-energy charged-particle tracks are reconstructed by measuring the relative times and positions of the drifted Cherenkov photons. A first experimental test the OTPC concept was performed at the Fermilab Test-Beam Facility using a 40 kg cylindrical water volume, which was instrumented with an array of small, commercial MCP-PMTs in combination with optical mirrors. The initial test-beam run examined the detector response to multi-GeV muons. Approximately 80 Cherenkov photons are detected for a through-going muon track in a total event duration of about 2 ns. By measuring the time-of-arrival and the position of these photons at the surface of the detector to better than 100 ps and a few mm, we measure a 3D spatial resolution of 15 mm on the particle track. The application of this technique to larger-scale water-based neutrino detectors will be discussed.