The KM3NeT Digital Optical Module: a multi-PMT approach

Parallel talk presented at the XXI International Workshop on Neutrino Telescopes - Padova 29 September - 3 October 2025 (https://agenda.infn.it/event/44606/) On behalf of the KM3NeT Collaboration Abstract: The KM3NeT Collaboration is deploying an advanced deep-sea neutrino detector in the Mediterranean Sea, aiming to explore neutrinos across a broad energy spectrum. This is achieved through two detectors, ARCA and ORCA, that share the same Cherenkov detection principle, but differ in their geometrical layout to address distinct physics goals. A central component of KM3NeT is its novel Digital Optical Module (DOM), which features 31 three-inch photomultiplier tubes within a single pressure-resistant glass sphere. This multi-PMT configuration marks a significant advancement over traditional single-PMT designs, offering a larger effective photocathode area and enabling superior timing accuracy,directional resolution, and calibration capabilities. To meet the demands of large-scale deployment (6210 DOMs are foreseen in total for the full-size detectors), the DOMs are assembled simultaneously at eight different integration sites using a rigorously standardized process. This talk will give an overview of the KM3NeT optical module technology and the integration strategy adopted to support large-scale deployment.