doi:10.1016/j.nima.2026.171585engAntolín, I.Castel, J.F.Dafni, T.Ferrer-Ribas, E.Galán, J.Huerva, A.García Irastorza, I.Luzón, G.Margalejo, C.Mirallas, H.Obis, L.Porrón, J.Puyuelo, M.J.Ruz, J.Vogel, J.K.Axion–nucleon sensitivity using ultra-low background Micromegas detectors for the International Axion ObservatoryART-2026-149027The International Axion Observatory (IAXO) aims to detect ultra-light bosonic dark matter candidates by combining strong magnetic fields, X-ray optics, and ultra-low background detectors. This work investigates the efficiency and sensitivity of various Micromegas detector configurations within IAXO, with a particular focus on the challenging axion–nucleon coupling channel. Through detailed simulations, we evaluate the intrinsic efficiency of the IAXO-D1 prototype, exploring both conventional argon-isobutane gas mixtures and a custom blend composed of 48.85% xenon, 48.85% neon, and 2.3% isobutane, under different pressure conditions. Detector responses are studied across a range of axion spectra. To support this analysis, a dedicated simulation framework was developed by integrating the Rare Event Searches Toolkit (REST) with Garfield++, Magboltz, and Geant4. The results highlight that Micromegas detectors operated with the xenon–neon-based gas mixture exhibit a marked improvement in performance compared to the nominal IAXO-D1 baseline configuration, with a signal-to-noise ratio enhancement of up to a factor of 3.7 in the case of axion–nucleon coupling sensitivity.2026http://zaguan.unizar.es/record/17100010.1016/j.nima.2026.171585http://zaguan.unizar.es/record/171000oai:zaguan.unizar.es:171000info:eu-repo/grantAgreement/ES/AEI/PID2019-108122GB-C31info:eu-repo/grantAgreement/ES/AEI/PID2022-137268NB-C51info:eu-repo/grantAgreement/EC/H2020/802836/EU/Axions and relatives across different mass scales/AxScaleThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 802836-AxScaleNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1089 (2026), 171585 [11 pp.]byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess