Development of Germanium (Ge) Ring Contact Detectors for Ge-based Neutrinoless Double-Beta Decay Experiment

The next generation of neutrinoless double beta (0νββ) decay experiments aims to achieve sensitivity to a decay with a half-life of ~10²⁸ years. A germanium-76 (Ge-76)-based experiment holds significant discovery potential for this rare decay process due to its excellent energy resolution and ability to reject scattered gamma-ray events. LEGEND-1000 prioritizes large-size detectors (>3 kg per detector) to further reduce backgrounds, complexity, and cost. This presentation will delve into the development of large-size Ge detectors fabricated in a novel ring contact (GeRC) geometry using high-purity Ge crystals grown at USD. The GeRC detector, a collaborative effort among ORNL, UNC, TAMU, and USD, has undergone significant improvements since its inception. In 2022, an initial GeRC detector was fabricated at TAMU and subsequently tested at UNC. Although this first iteration did not meet our expectations, it provided valuable insights for further enhancements.

We have since optimized several technical aspects at USD, including the machining and surface grinding treatment processes. We have developed a technology for producing pure lithium powder and established a process for lithium painting and lithium diffusion. By establishing an upgraded workshop at USD, we are now better equipped to study GeRC detectors comprehensively. Leveraging the experience gained from TAMU, we are poised to fabricate a detector at USD. In this presentation, we will share preliminary results obtained from the GeRC detector fabricated at USD, utilizing crystals grown exclusively at USD.