Characterization of inverted coaxial Ge detectors in GERDA for future double- decay experiments

Area of Science:

• Nuclear Physics
• Particle Physics
• Experimental Physics

Background:

• Searches for neutrinoless double-beta decay are crucial for understanding neutrino properties.
• Increasing detector mass is essential for enhancing the sensitivity of future experiments.
• Traditional germanium detectors have limitations in mass or resolution.

Purpose of the Study:

• To characterize and test prototype inverted coaxial (IC) germanium detectors for neutrinoless double-beta decay searches.
• To evaluate the performance of IC detectors in terms of energy resolution and background levels.
• To confirm the feasibility of IC detectors for next-generation experiments.

Main Methods:

• Manufactured five prototype detectors using germanium enriched to 88% in Germanium-76 (⁷⁶Ge).
• Utilized inverted coaxial (IC) geometry to combine large mass with good energy resolution and pulse shape discrimination.
• Operated detectors in both vacuum cryostat and liquid argon environments within the GERmanium Detector Array (Gerda) setup.

Main Results:

• Achieved energy resolutions of approximately 2.1 keV FWHM at the Q-value for ⁷⁶Ge double-beta decay.
• Measured a background index of approximately 1.5 x 10⁻³ counts/(kg·keV·y) after 18 months of operation in Gerda.
• Demonstrated satisfactory performance in both vacuum and liquid argon conditions.

Conclusions:

• Inverted coaxial germanium detectors are a viable technology for large-scale neutrinoless double-beta decay experiments.
• The tested prototypes meet the stringent requirements for low background and high resolution.
• This work supports the development of the next-generation LEGEND experiment.