arXiv subjects

Alejandro Díaz-Morcillo

Publications and source records attributed to Alejandro Díaz-Morcillo.

11 recordsLinked to original sources

arXiv2026

Resonant heterodyne conversion applied to a low-frequency haloscope for dark matter axion searches in the 1-35 MHz range

We study resonant heterodyne up-conversion in the RADES-BabyIAXO haloscope as a method to search for low-mass dark matter axions using microwave cavities. Starting from axion electrodynamics, we derive the axion-induced source term and the power extracted through a readout mode, explicitly accounting for the finite axion linewidth. This leads to effective quality factors that determine the pump-axion mixing, detection bandwidth, and detected signal power. We extend the BI-RME 3D full-wave formulation to heterodyne axion detection in a realistic two-port cavity, including pump leakage into the readout channel. Applying the formalism to the largest RADES-BabyIAXO cavity identifies the $\mathrm{quasi\textrm{-}TE}_{011}-\mathrm{quasi\textrm{-}TM}_{010}$ mode pair as a favorable configuration, enabling sensitivity to axion frequencies between 0.9 and 34.6 MHz. Analytical and full-wave predictions show excellent agreement at resonance, while the full-wave model provides a more accurate description off resonance and allows a precise characterization of the pump leakage. We also derive the optimal port couplings that maximize the scanning rate. Sensitivity projections for cryogenic copper and superconducting niobium cavities indicate that, under thermal-noise-limited conditions and assuming sufficient pump-leakage rejection, the experiment could probe axion-photon couplings down to $10^{-15}\,\mathrm{GeV}^{-1}$ at 90% confidence level, representing a significant improvement over previous heterodyne-based searches.

hep-ex↗

arXiv2026

A study of multicavity concept applied to hexagonal coaxial haloscopes

In this work, a study on the development of scalable multicavity architectures for axion haloscopes, based on a hexagonal coaxial geometry operating at $30$ GHz frequencies, is presented. To enhance the scanning rate and sensitivity within the limited volume of experimental magnet bores, the transition from a baseline single-cavity design to dual and triple-subcavity configurations is investigated. A novel tuning mechanism based on the rotation of one or two inner hexagonal prisms is implemented, providing a robust method to shift the resonant frequency while maintaining high form and quality factors. The results show that the triple-subcavity design achieves an improvement of $\times3$ over the single-cavity baseline. The scaling potential of quad-subcavity architectures under a strict radial constraint of $25$ mm is further explored. Theoretical analysis confirms that a four-subcavity system is feasible within a certain radial clearance, provided that wall thicknesses are strategically optimised to ensure frequency stability. The practical challenges associated with mode splitting, manufacturing tolerances, and thermal management in these high-order systems are also discussed. This one-port multicavity approach offers a viable path toward increasing the sensitive volume of haloscopes, enabling more efficient exploration of the axion dark matter parameter space in high-frequency regimes.

hep-ex↗

arXiv2026

Global detector network to search for high-frequency gravitational waves (GravNet): conceptual design

We propose GravNet (Global detector network to search for high-frequency gravitational waves), a novel experimental scheme enabling the search for gravitational waves in the MHz to GHz frequency range. Such high-frequency gravitational waves could arise from a variety of phenomena connected to some of the most pressing and fundamental questions in modern cosmology. The GravNet concept is based on synchronous measurements of signals from multiple experimental measurement devices operating at geographically separated locations. While gravitational-wave-induced signatures may be present in the signal of a single detector, distinguishing them from instrumental or environmental noise is highly challenging. By analyzing correlations between signals from several distant detectors, the detection significance is substantially enhanced, while simultaneously enabling studies of the nature and origin of the gravitational-wave signal. In this work, we discuss the GravNet concept specifically in the context of cavities operated in strong magnetic fields, as these currently represent the most technically mature and experimentally advanced realization of the scheme. As part of this proposal, a first demonstration experiment using a non-superconducting cavity has been performed, providing the basis for the data-analysis strategies discussed in this work. Finally, we outline the prospects and future development of GravNet as a global network for high-frequency gravitational-wave searches.

astro-ph.IM↗

arXiv2026

The COSMIC WISPers White Paper: The physics case for Weakly Interacting Slim Particles

Axions and other very weakly interacting slim particles (WISPs), with masses below 1 GeV, arise naturally in many extensions of the Standard Model of particle physics. In particular, they could offer a new framework to explain the nature of dark matter and may help address a range of puzzling observations in astrophysics and particle physics. This review provides an overview of ongoing WISP searches and outlines the prospects for the next decade, spanning their theoretical motivation, indirect signatures in astrophysical observations, and dedicated laboratory experiments. It is based on the work carried on by the EU-funded COST Action ``Cosmic WISPers in the Dark Universe: Theory, astrophysics, and experiments'' (CA21106, https://www.cost.eu/actions/CA21106). This network plays a key role in coordinating and supporting WISP searches across Europe, while also contributing to the development of a roadmap aimed at securing European leadership in this research area. It is emphasized that Europe is currently pursuing a rich, diverse, and cost-effective experimental program, with the potential to deliver one or more transformative discoveries.

hep-ph↗

arXiv2025

Enhancement of dark-photon haloscope sensitivity with degenerate modes: toward axion-level form factor and polarization determination

The dark photon has been postulated as a potential constituent of dark matter, exhibiting notable similarities to the axion. The primary distinction between the two particles lies in the nature of their respective fields: the dark photon field is a vector field with a polarization direction that remains undetermined. This work explores the prospect of utilizing three degenerate modes for scanning the three dimensions of space in order to mitigate the low form factor expected in the detection of the dark photon due to their unknown polarization. The employment of an haloscope with three orthogonal and degenerate modes in conjunction with the coherent sum of signals is demonstrated in this work in order to enhance the dark photon form factor up to the axion form factor, and to determine the direction of the dark photon polarization vector. We show in this manuscript that the maximum form factor is achieved in cavities of cubic, spherical, and cylindrical geometries, considering the introduction of tuning elements. To achieve this adequately, some conditions reviewed in this article must be fulfilled in the resonant cavity, leading to uncertainties in the final measurement. Finally, this technique can allow the simultaneous search for dark matter axions and dark photons, and to the knowledge of the authors, the method shown in this work is the most effective one for detecting dark photon with microwave resonant cavities.

hep-ph↗

arXiv2025

Multiple-cavities interferometric analysis for dark matter axions directional-sensitive search based on signal cross-correlation processing

Current axion detection limits neglect the relevance of the relative velocity between the axion field and the detectors. However, this aspect can lead to a daily modulation of the detected axion signal. In this work, we calculate the cross-correlation of various signals potentially originated in multiple-cavity setups, and we analyze how the signal-to-noise ratio and directional sensitivity depend on the signal cross-correlation among multiple cavities. The signal-to-noise ratio after cross-correlation exhibits a greater rate of increase over time compared to the power-summation technique, making it clear that this method could be potentially employed in a real setup for the reduction of the exposure time. For the study of the daily modulation, three interferometric experiments have been proposed in this manuscript: (i) three rectangular cavities in different Earth locations; (ii) three rectangular cavities located in the same Earth spot but oriented towards different perpendicular directions; (iii) six rectangular cavities in the same Earth location but oriented towards different directions. In each set-up, we have simulated three different cavity lengths. Similar results have been found for the cases (i) and (ii): when the highest length upon the three proposed is considered, a phase difference between the recorded voltages of more than $2^{\circ}$ has been obtained with our numerical calculations. We observe a daily modulation in the imaginary part of the signals cross-correlation for experiment (iii), that could be potentially used for the characterization of the axion velocity distribution. To the knowledge of the authors, this is the first time that the cross-correlation technique has been applied to the directional sensitivity analysis of an array of haloscopes.

hep-ex↗

arXiv2024

Dark Matter Axion Detection with Neural Networks at Ultra-Low Signal-to-Noise Ratio

We present the first analysis of Dark Matter axion detection applying neural networks for the improvement of sensitivity. The main sources of thermal noise from a typical read-out chain are simulated, constituted by resonant and amplifier noises. With this purpose, an advanced modal method employed in electromagnetic modal analysis for the design of complex microwave circuits is applied. A feedforward neural network is used for a boolean decision (there is axion or only noise), and robust results are obtained: the neural network can improve by a factor of $5\cdot 10^{3}$ the integration time needed to reach a given signal to noise ratio. This could either significantly reduce measurement times or achieve better sensitivities with the same exposure durations.

hep-ex↗

arXiv2024

Study of a cubic cavity resonator for gravitational waves detection in the microwave frequency range

The direct detection of gravitational waves (GWs) of frequencies above MHz has recently received considerable attention. In this work we present a precise study of the reach of a cubic cavity resonator to GWs in the microwave range, using for the first time tools allowing to perform realistic simulations. Concretely, the BI-RME 3D method, which allows us to obtain not only the detected power but also the detected voltage (magnitude and phase), is used here. After analyzing three cubic cavities for different frequencies and working simultaneously with three different degenerate modes at each cavity, we conclude that the sensitivity of the experiment is strongly dependent on the polarization and incidence angle of the GW. The presented experiment can reach sensitivities up to $ 1 \cdot 10^{-19}$ at 100\, MHz, $ 2 \cdot 10^{-20}$ at 1\, GHz, and $ 6 \cdot 10^{-19}$ at 10\, GHz for optimal angles and polarizations, and where in all cases we assumed an integration time of $Δt = 1$ ms. These results provide a strong case for further developing the use of cavities to detect GWs. Moreover, the possibility of analyzing the detected voltage (magnitude and phase) opens a new interferometric detection scheme based on the combination of the detected signals from multiple cavities.

hep-ph↗

arXiv2024

Microwave Technologies in Experiments for Detection of Dark Matter Axions

This article reviews different microwave technologies used in dark matter axion detection experiments with resonant cavities. The general concepts of the experiment are presented and ways to optimize the design parameters of microwave resonators are discussed. Additionally, different frequency tuning systems are described. Finally, research lines where microwave engineering can contribute to this kind of axion detection are presented.

physics.ins-det↗

arXiv2022

The Canfranc Axion Detection Experiment (CADEx): Search for axions at 90 GHz with Kinetic Inductance Detectors

We propose a novel experiment, the Canfranc Axion Detection Experiment (CADEx), to probe dark matter axions with masses in the range 330-460 $μ$eV, within the W-band (80-110 GHz), an unexplored parameter space in the well-motivated dark matter window of Quantum ChromoDynamics (QCD) axions. The experimental design consists of a microwave resonant cavity haloscope in a high static magnetic field coupled to a highly sensitive detecting system based on Kinetic Inductance Detectors via optimized quasi-optics (horns and mirrors). The experiment is in preparation and will be installed in the dilution refrigerator of the Canfranc Underground Laboratory. Sensitivity forecasts for axion detection with CADEx, together with the potential of the experiment to search for dark photons, are presented.

hep-ex↗

arXiv2018

Axion Searches with Microwave Filters: the RADES project

We propose, design and construct a variant of the conventional axion haloscope concept that could be competitive in the search for dark matter axions of masses in the decade 10-100 $μ$eV. Theses masses are located somewhat above the mass range in which existing experiments have reached sensitivity to benchmark QCD axion models. Our haloscope consists of an array of small microwave cavities connected by rectangular irises, in an arrangement commonly used in radio-frequency filters. The size of the unit cavity determines the main resonant frequency, while the possibility to connect a {large} number of cavities allows to reach large detection volumes. We develop the theoretical framework of the detection concept, and present design prescriptions to optimize detection capabilities. We describe the design and realization of a first small-scale prototype of this concept, called Relic Axion Detector Exploratory Setup (RADES). It consists of a copper-coated stainless steel five-cavities microwave filter with the detecting mode operating at around 8.4 GHz. This structure has been electromagnetically characterized at 2 K and 298 K, and it is now placed in ultra-high vacuum in one of the twin-bores of the 9 T CAST dipole magnet at CERN. We describe the data acquisition system developed for relic axion detection, and present preliminary results of the electromagnetic properties of the microwave filter, which show the potential of filters to reach QCD axion window sensitivity at X-band frequencies.

hep-ex↗