Title : The Nuova Officina Assergi: A facility for the mass production and characterization of large-area SiPM detectors
Abstract:
Silicon Photomultipliers (SiPMs) are increasingly replacing conventional photomultiplier tubes (PMTs) owing to their outstanding performance characteristics, including single-photon sensitivity, immunity to strong magnetic fields, excellent spatial resolution, high fill factor, and intrinsic radiopurity. While SiPM technology is already widely employed in medical imaging applications, its adoption is rapidly expanding in rare-event searches and high-energy physics experiments, where low-background operation and high detection efficiency are essential. One of the most ambitious projects relying on this technology is DarkSide-20k (DS-20k), a next-generation direct dark matter search experiment currently under construction in Hall C of the Gran Sasso National Laboratories (LNGS), Italy.
The detector is based on a dual-phase Time Projection Chamber (TPC) containing a fiducial mass of 20 tonnes of underground argon (UAr), characterized by an exceptionally low ^39Ar activity. An extensive campaign of material screening and detector optimization have enabled the DarkSide Collaboration to achieve a projected radiogenic background of only 0.1 events in a 200 tonne·year exposure after all the analysis selection cuts. The scintillation light produced in both the liquid and gaseous phases of the TPC will be detected by two optical planes, each covering an area of approximately 10.5 m² and instrumented with arrays of high-performance cryogenic SiPMs. To support the large-scale production and integration of these photosensors, the Nuova Officina Assergi (NOA) has been realized at LNGS. The infrastructure fully operational since 2023, is an ISO Class 6 cleanroom facility dedicated to the assembly, packaging, and characterization of large-area SiPM detectors. NOA is equipped with advanced packaging machinery and dedicated instrumentation for device handling, quality assurance, and early diagnostics in a controlled low-contamination environment. The facility is currently carrying out the mass production of more than 500 of SiPM-based Photo Detection Units (PDUs) each one 20 cm2 x 20 cm2, with 50% of the production already completed. This contribution shows the DS-20k photosensor production workflow, summarizes the current status of mass production and testing activities at NOA and highlights the capabilities of the NOA infrastructure as a future resource for the broader scientific community interested in large-area SiPM technologies.
