Speaker
Description
Segmented high-purity germanium (HPGe) detectors are essential tools in advanced gamma spectroscopy. However, many of their technical and manufacturing details remain proprietary to industry. To overcome this limitation, the Italian Institute for Nuclear Physics funded the N3G Project, aimed at developing new segmented HPGe detectors while building in-house expertise for their design, production, operation and maintenance.
In this framework, we present the design and qualification of a cryogenic capsule conceived to host a coaxial high-purity germanium detector and to operate it under high-vacuum conditions at liquid nitrogen temperature. Particular attention is given to mechanical robustness, thermal compatibility and long-term vacuum integrity.
A comprehensive qualification workflow is described, including helium mass spectrometry leak detection, local helium sniffing tests and iterative optimization of the sealing through controlled fastening adjustments. Particular emphasis is placed on the sealing strategy, based on metal gaskets such as HelicoFlex seals, selected for their robustness and suitability in high-vacuum and cryogenic environments. The role of non-evaporable getters is also discussed, highlighting their function as chemical pumps capable of enhancing and stabilizing the static vacuum level over extended operation periods.
The sealing tests demonstrated excellent leak-tight performance: over a five-day monitoring period, the internal pressure increased by only about 2e−5 mbar, confirming the high integrity of the adopted sealing solutions. These results validate the effectiveness of the combined approach—metallic seals and getter-based vacuum stabilization—and provide a solid and reproducible technological basis for future detector developments.
Finally, the mechanical support structures of the detector are described in detail. These components have been specifically designed to ensure stable and safe handling of the device, while minimizing mechanical stress and avoiding any direct contact that could damage its sensitive surfaces. The support system enables the detector to be oriented in any spatial configuration, providing full flexibility during installation, testing and operation, without compromising its structural integrity or performance.