Silicon Photosensor Development for the Low-Background Frontier

This proposal aims to leverage the UK's world-leading silicon detector integration capability to grow UK leadership in large silicon photo-multiplier (SiPM) array detectors for low-background physics.

Low background physics experiments address some of the most fundamental open questions in science today: what is most of the matter in the universe made of? how does dark matter interact with us? why do we live in a matter-dominated universe? Experiments studying these questions at the cosmic and intensity frontiers of particle physics increasingly employ detectors filled with liquid noble gases. Liquid nobles produce scintillation light when particles interact, which is detected with arrays of photo-sensor detectors.

Silicon detectors have revolutionised particle physics at the energy frontier, and are increasingly important at the intensity and cosmic frontiers. The major challenge in dark matter and low-energy neutrino physics is to maximise signal detection efficiency whilst achieving ultra-low background interaction rates. There is a growing consensus across liquid noble dark matter and neutrino experiments that silicon photo-multiplier (SiPM) detectors are the key enabling technology to meet these challenges. The importance of developing UK leadership in this area was recognised in the recent STFC Dark Matter Strategic Review:

"The development of SiPMs for future large-scale direct-DM searches using noble gases provides the opportunity for the UK to invest in early R&D in order to achieve technological leadership in any future next generation experiment. R&D would focus on the design, production and testing of large SiPM tile arrays including electronics."

This proposal focuses on the design, production and testing of large SiPM tile arrays including electronics. The state-of-the-art in integration of large SiPM tile arrays for low-background experiments today is the DarkSide photon detector module (PDM). The PDM consists of an array of ~1 cm2 SiPMs ('tiles') bonded to a substrate to form a 25 cm2 photosensitive area, connected to cryogenic front end electronics that combine the signal from all tiles and condition it. This proposal aims to develop technological leadership for the future through:
1. R&D: on developing tiled Si array detectors for low-background experiments beyond the current state-of-the-art. We will develop new integration and readout strategies to reduce radioactivity and expand the physics reach of future experiments, potentially hosted at Boulby Underground Laboratory;
2. Knowledge Exchange: leveraging knowledge built up in the Global Argon Dark Matter Collaboration and world-leading UK facilities, we will develop production processes and expertise to manufacture and test improved, lower-background PDMs; and,
3. Capacity building: demonstrating capacity to build and test PDMs for the global next-generation liquid noble gas experiment through producing PDMs for a sub-system of DarkSide's outer detector.

To execute this ambitious programme we bring together a team of experts that have built silicon detectors for the Large Hadron Collider and space-based experiments, dark matter and neutrino physics experimentalists pushing the frontiers of ultra-low radioactivity, and theorists expanding the horizons for new physics searches based on advances in instrumentation.

Detector development is the engine of discovery in particle physics. This proposal aims to develop new technologies to ensure vitality of our field in the UK, and to future-proof STFC research through active R&D, with outstanding discovery potential for the future.