WG1 aims to focus on the studies and development of novel photo-detectors, which include solid-state (SiPM) and vacuum-based (MCP-PMT) photo sensors, and provide an exchange of information with DRD1 on gas-based photo-detectors. The following topics will be discussed:

• The tolerance of photon detectors to irradiation;
• Long-term operation of photon detectors and mitigation measures to prolong their lifetime, e.g., low gain operation and annealing of SiPMs;
• Operation of photon detectors in other extreme conditions, including cryogenic and high magnetic field operations;
• Development of SiPMs with improved timing;
• Development of large-area SiPMs;
• Studies of large-area vacuum photo sensors, e.g., LAPPDs;
• Development of fine granularity detectors for future high-rate experiments;
• Development of new technologies and their feasibility studies: CMOS-SPAD-based sensors, SiPMs with different internal structures, back-side illuminated SiPMs, etc;
• Studies of novel materials for photon detection, e.g., Ge-on-Si APDs;
• Studies of hybrid photon sensors, e.g., Timepix-HPDs and MCP-HPDs;
• Studies and development of read-out electronics suitable for extreme environments (high radiation, high magnetic field, low temperature);
• Development of interconnection techniques for optimal sensors and readout electronics integration;
• Simulations of photo-detector response.

Group members will work on standardizing procedures for the characterization of photon detectors, especially after exposure to extreme environmental conditions. The goal of the information and knowledge flow is to advance the detectors for PID and TOF identification systems of future HEP experiments. The group will also have regular knowledge exchange with groups working on gas-based photodetectors (DRD1), on the development of photosensors for cryogenic detectors (DRD2) and for calorimeters (DRD6), as well as with groups working on novel concepts in read-out electronics (DRD7).