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

The pursuit of neutrinoless double beta decay (0νββ) demands highly sensitive detector technology capable of probing half-lives on the order of 10²⁸ years. Germanium detectors have excellent energy resolution and background rejection techniques. They are able to be enriched in the Ge-76 isotope to levels >90% making Ge-76 a leading candidate for a 0vBB search. Larger-mass detectors are desirable since they reduce the required number of cables and readout electronics, which can produce radioactive backgrounds. This presentation highlights the development of germanium detectors utilizing a novel ring contact (GeRC) geometry, leveraging high-purity Ge crystals grown at the University of South Dakota (USD).

Building upon prior fabrication efforts and insights from earlier prototypes, our current research explores advanced techniques in GeRC detector production, including improvements in machining, surface treatments, and lithium diffusion methods. The next phase involves fabricating a small GeRC detector as a precursor to large-scale GeRC detectors, using optimized lithium diffusion technology. Enhanced glovebox capabilities and higher-purity lithium-in-oil suspensions are employed to refine the diffusion process and validate theoretical models predicting similar barrier heights for varying donor lithium concentrations (~10¹⁴ vs. ~10¹⁶ cm⁻³) at cryogenic temperatures (77 K) to minimize the dead layer caused by lithium diffusion.

Preliminary results from these advancements will be presented, demonstrating progress toward the next generation of detectors for 0νββ experiments.