Resumen: RADES (Relic Axion Detector Exploratory Setup) is a project with the goal of directly searching for axion dark matter above the 30µeV scale employing custom-made microwave filters in magnetic dipole fields. Currently RADES is taking data at the LHC dipole of the CAST experiment. In the long term, the RADES cavities are envisioned to take data in the BabyIAXO magnet. In this article we report on the modelling, building and characterisation of an optimised microwave-filter design with alternating irises that exploits maximal coupling to axions while being scalable in length without suffering from mode-mixing. We develop the mathematical formalism and theoretical study which justifies the performance of the chosen design. We also point towards the applicability of this formalism to optimise the MADMAX dielectric haloscopes. Idioma: Inglés DOI: 10.1007/JHEP07(2020)084 Año: 2020 Publicado en: Journal of High Energy Physics 2020, 7 (2020), 84 [26 pp.] ISSN: 1126-6708 Factor impacto JCR: 5.81 (2020) Categ. JCR: PHYSICS, PARTICLES & FIELDS rank: 5 / 29 = 0.172 (2020) - Q1 - T1 Factor impacto SCIMAGO: 0.998 - Nuclear and High Energy Physics (Q2)