doi:10.12688/openreseurope.19258.2engCastel Pablo, Juan FranciscoCebrián Guajardo, SusanaDafni, TheopistiDíez Ibáñez, DavidGalán Lacarra, JavierGarcía Pascual, Juan AntonioEzquerro Sastre, ÁlvaroGarcía Irastorza, IgorLuzón Marco, GloriaMargalejo Blasco, CristinaMirallas Sánchez, HéctorObis Aparicio, LuisOrtiz de Solórzano, AlfonsoPérez Lázaro, ÓscarPorrón Lafuente, JorgeJiménez Puyuelo, MaríaMicromegas with GEM preamplification for enhanced energy threshold in low-background gaseous time projection chambersART-2025-144770Background We develop the concept of a Micromegas readout plane with an additional GEM preamplification stage placed a few millimetres above it to increase the maximum effective gain of the combined readout. Methods We implement it and test it in realistic conditions for its application to low-background dark matter searches like the TREX-DM experiment. For this, we use a Micromegas of Microbulk type, built with radiopure materials. Results We report on GEM effective extra gain factors of about 90, 50 and 20 in 1, 4 and 10 bar of Ar-1%iC4H10. These results are obtained in a small test chamber allowing for systematic scanning of voltages and pressures. In addition, a TREX-DM full-scale set-up has also been built and tested, featuring a replica of the fully-patterned TREX-DM Microbulk readout. Conclusions The results here obtained show promise to lower the threshold of the experiment down to 50 eV ee , corresponding to substantially enhanced sensitivity to low-mass WIMPs.2025http://zaguan.unizar.es/record/16223210.12688/openreseurope.19258.2http://zaguan.unizar.es/record/162232oai:zaguan.unizar.es:162232info:eu-repo/grantAgreement/EC/H2020/101026819/EU/Low background techniques on particle detectors for Rare Event Searches/LOBRESThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 101026819-LOBRESinfo:eu-repo/grantAgreement/EC/H2020/788781/EU/Towards the detection of the axion with the International Axion Observatory/IAXOplusThis project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No H2020 788781-IAXOplusinfo:eu-repo/grantAgreement/ES/MICINN/PID2019-108122GB-C31info:eu-repo/grantAgreement/ES/MICINN/PID2022-137268NB-C51Open Research Europe 5 (2025), 53byhttps://creativecommons.org/licenses/by/4.0/deed.esinfo:eu-repo/semantics/openAccess