The Second LHAASO Collaboration Conference in 2026 & The Academic Symposium for the 10th Anniversary of the LHAASO collaboration

The LHAASO-WCDA array adopts 3-inch photomultiplier tubes (PMTs) for the small-PMT channels of its WCDA-2 and WCDA-3 sub-arrays. A total of 2,220 3-inch PMTs were fully installed in 2021 and have been in continuous operation for over five years. Notably, HZC Photonics, the original manufacturer of the deployed 3-inch PMTs, has terminated the production of this specific model. As a result, subsequent equipment replacement and maintenance necessitate the adaptation of new PMT models to the original high-voltage system. This poster systematically summarizes the in-service operational status of the 3-inch PMT system, analyzes typical faults and failure causes of defective PMTs accumulated during long-term operation, and proposes a targeted repair and maintenance scheme.Title: Operational Status and Maintenance Scheme for 3-inch PMTs of LHAASO-WCDA Array.