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arXiv · 2510.01913

Dark characterization of Ti/Al LEKIDs for the search of axions in the W-band

Victor Rollano·Alejandro Pascual Laguna·David Rodriguez·Martino Calvo·Maria Teresa Magaz·Daniel Granados·Alessandro Monfardini·Alicia Gomez
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Abstract

We report the electrical (dark) characterization of lumped-element kinetic inductance detectors (LEKIDs) fabricated from a Titanium/Aluminum bilayer and designed for broadband absorption in the W-band (75-110 GHz). These detectors are prototypes for future QCD axion search experiments within the Canfranc Axion Detection Experiment (CADEx), which demand sub 1e-19 W/Hz^0.5 sensitivities under low optical backgrounds. We combine a Mattis-Bardeen analysis to the temperature dependence of the detector parameters with noise spectroscopy to determine the electrical noise equivalent power (NEP). The minimum measured value for the electrical NEP is 3e-19 W/Hz0.5. Across the measured temperature range, we find that quasiparticle lifetime deviates from the expected BCS recombination law. Our analysis suggests that non-equilibrium relaxation is governed by spatial inhomogeneities in the superconducting gap and phonon diffusion effects. This work sets the road-map to achieve suitable and ultra-sensitive detectors in the W-band for dark matter axion search experiments.

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Victor Rollano, Alejandro Pascual Laguna, David Rodriguez, Martino Calvo, Maria Teresa Magaz, Daniel Granados, Alessandro Monfardini, Alicia Gomez. 2025-10-02. Dark characterization of Ti/Al LEKIDs for the search of axions in the W-band. https://arxiv.org/abs/2510.01913

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