In recent years, there have been significant advancements in gaseous detectors, particularly Time Projection Chambers (TPCs), for detecting low-energy rare events. These detectors are sensitive to the charge released in the gas by ionizing radiation with energy deposits as low as few tens of electronvolts and also provide the topology of the ionization trail when coupled to suitable Micro Pattern Gas Detectors. Since 2015, the CYGNO collaboration has been developing a TPC, operated with a He:CF4 gas mixture at atmospheric pressure, based on a triple Gas Electron Multiplier (GEM) stack to amplify primary ionization charges and produce light. The innovative optical readout technology adopted combines CMOS-based Active Pixel Sensors with fast PMTs, allowing detailed 3D reconstruction of events while keeping sensors outside the sensitive volume and thus minimising background contamination.
The seminar will focus on the Long Imaging ModulE (LIME), a prototype with an active 50-litre volume. LIME has demonstrated linearity in the response to low energy electronic recoils from 4 keV to 40 keV and a very good discriminating power between electronic and nuclear recoils also below 10 keV. The results obtained in the first two data-taking runs performed in the INFN underground laboratories at Gran Sasso, where over one million events were collected with and without a gamma copper shielding, will also be presented together with promising results of on-going R&D activities on Negative Ion Drift (NID) operation and hydrogen enriched gas mixtures.
Finally, the design of the upcoming demonstrator, which will comprise a sensitive volume of about 0.4 cubic meters and is expected to start taking underground data in 2025, will be illustrated, together with the physics reach of a future O(30) m3 experiment. The seminar will showcase the promising performance of the LIME prototype and the potential of this optical readout technology for future low-energy rare event detection experiments.
Eraldo Oliveri (EP-DT)