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Description
The CMS Improved Resistive Plate Chambers (iRPCs) are a key component of the muon detection system for operation during the High-Luminosity LHC era. Their long-term performance depends on the stability of the high pressure laminate (HPL) electrodes. Based on previous studies of iRPC aging performed at the CERN Gamma Irradiation Facility (GIF++), this work investigates the microscopic and chemical modifications induced in irradiated HPL samples and their possible connection to detector degradation. Samples extracted from linseed-oil-coated HPL electrodes exposed to gamma irradiation were analyzed using complementary diagnostic techniques, including Raman spectroscopy, photoluminescence, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The combined results indicate significant differences between irradiated and non-irradiated samples, suggesting the formation of radiation-induced defects and chemical transformations in the HPL surface layer. In particular, the observation of fluorine-containing deposits and localized structural degradation supports models relating detector aging to interactions between radiation products, gas by-products and electrode materials.