On the development of new tuning and inter-coupling techniques using ferroelectric materials in the detection of dark matter axions

Tuning is an essential requirement for the search of dark matter axions employing haloscopes since its mass is not known yet to the scientific community. At the present day, most haloscope tuning systems are based on mechanical devices which can lead to failures due to the complexity of the environment in which they are used. However, the electronic tuning making use of ferroelectric materials can provide a path that is less vulnerable to mechanical failures and thus complements and expands current tuning systems. In this work, we present and design a novel technique for using the ferroelectric Potassium Tantalate (KTaO3 or KTO) material as a tuning element in haloscopes based on coupled microwave cavities. In this line, the structures used in the Relic Axion Detector Exploratory Setup (RADES) group are based on several cavities that are connected by metallic irises, which act as interresonator coupling elements. In this article, we also show how to use these KTaO3 films as interresonator couplings between cavities, instead of inductive or capacitive metallic windows used in the past. These two techniques represent a crucial upgrade over the current systems employed in the dark matter axions community, achieving a tuning range of 2.23% which represents a major improvement as compared to previousworks (<0.1%) for the same class of tuning systems. The theoretical and simulated results shown in this work demonstrate the interest of the novel techniques proposed for the incorporation of this kind of ferroelectric media in multicavity resonant haloscopes in the search for dark matter axions.This work was supported in part by the ‘‘MCIN/AEI/10.13039/501100011033/’’ and ‘‘European Regional Development Fund (ERDF) A way of making Europe’’ under Grant PID2019-108122GB-C33, in part by the ‘‘MCIN/AEI/10.13039/501100011033/’’ and ‘‘European Social Fund (ESF) Investing in your future’’ under Grant FPI BES-2017-079787, and in part by the European Research Council (ERC) under Grant ERC-2018-StG-802836 (AxScale)

Design of new resonant haloscopes in the search for the dark matter axion: A review of the first steps in the RADES collaboration

With the increasing interest in dark matter axion detection through haloscopes, in which different international groups are currently involved, the RADES group was established in 2016 with the goal of developing very sensitive detection systems to be operated in dipole magnets. This review deals with the work developed by this collaboration during its first five years: from the first designs—based on the multi-cavity concept, aiming to increase the haloscope volume, and thereby improve sensitivity—to their evolution, data acquisition design, and finally, the first experimental run. Moreover, the envisaged work within RADES for both dipole and solenoid magnets in the short and medium term is also presented.This work has been funded by the Spanish Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under projects FPA-2016-76978-C3-2-P (supported by the grant FPI BES-2017-079787) and PID2019-108122GB-C33, and was supported by the CERN Doctoral Studentship programme. The research leading to these results has received funding from the European Research Council under grant ERC-2018-StG-802836 (AxScale project). IGI acknowledges support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project)

First results of the CAST-RADES haloscope search for axions at 34.67 μeV

et al.We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ ≳ 4 × 10−13 GeV−1 over a mass range of 34.6738 μeV < ma < 34.6771 μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25 μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavities.Article funded by SCOAP3.This work has been funded by the Spanish Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project FPA-2016-76978-C3-2-P (supported by the grant FPI BES-2017-079787) and PID2019-108122GB-C33, and was supported by the CERN Doctoral Studentship programme. The research leading to these results has received funding from the European Research Council and BD, JG and SAC acknowledge support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project). BD also acknowledges fruitful discussions at MIAPP supported by DFG under EXC-2094 – 390783311. IGI acknowledges also support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project). JR has been supported by the Ramon y Cajal Fellowship 2012-10597, the grant PGC2018-095328-BI00(FEDER/Agencia estatal de investigación) and FSE-DGA2017-2019-E12/7R (Gobierno de Aragón/FEDER) (MINECO/FEDER), the EU through the ITN “Elusives” H2020-MSCA-ITN-2015/674896 and the Deutsche Forschungsgemeinschaft under grant SFB-1258 as a Mercator Fellow. CPG was supported by PROMETEO II/2014/050 of Generalitat Valenciana, FPA2014-57816-P of MINECO and by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreements 690575 and 674896. AM is supported by the European Research Council under Grant No. 742104.Peer reviewe

Scalable haloscopes for axion dark matter detection in the 30 µeV range with RADES

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.We thank Ciaran O’Hare for his generous and publicly available compilation of axion bounds https://github.com/cajohare /AxionLimits/. This work has been funded by the Spanish Ministerio de Economía, Industria y Competitividad – Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project FPA-2016-76978, and was supported by the CERN Doctoral Studentship programme. The research leading to these results has received funding from the European Research Council and BD, JG and SAC acknowledge support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project). IGI acknowledges also support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project). JR has been supported by the Ramon y Cajal Fellowship 2012-10597, the grant PGC2018-095328-B-I00(FEDER/Agencia estatal de investigaci´on) and FSE-DGA2017-2019-E12/7R (Gobierno de Aragón/FEDER) (MINECO/FEDER), the EU through the ITN “Elusives” H2020-MSCA-ITN-2015/674896 and the Deutsche Forschungsgemeinschaft under grant SFB-1258 as a Mercator Fellow. CPG was supported by PROMETEO II/2014/050 of Generalitat Valenciana, FPA2014-57816-P of MINECO and by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreements 690575 and 674896. AM is supported by the European Research Council under Grant No. 742104. We wish also to thank our colleagues at CAST and at CERN, in particular Marc Thiebert from the coating lab, Sergio Calatroni for many useful discussions, as well as the whole team of the CERN Central Cryogenic Laboratory for their support and advice in specific aspects of the project

Wide-band full-wave electromagnetic modal analysis of the coupling between dark-matter axions and photons in microwave resonators

The electromagnetic coupling axion–photon in a microwave cavity is revisited with the Boundary Integral-Resonant Mode Expansion (BI-RME) 3D technique. Such full-wave modal technique has been applied for the rigorous analysis of the excitation of a microwave cavity with an axion field. In this scenario, the electromagnetic field generated by the axion–photon coupling can be assumed to be driven by equivalent electrical charge and current densities. These densities have been inserted in the general BI-RME 3D equations, which express the RF electromagnetic field existing within a cavity as an integral involving the Dyadic Green’s functions of the cavity (under Coulomb gauge) as well as such densities. This method is able to take into account any arbitrary spatial and temporal variation of both magnitude and phase of the axion field. Next, we have obtained a simple network driven by the axion current source, which represents the coupling between the axion field and the resonant modes of the cavity. With this approach, it is possible to calculate the extracted and dissipated RF power as a function of frequency along a broad band and without Cauchy–Lorentz approximations, obtaining the spectrum of the electromagnetic field generated in the cavity, and dealing with modes relatively close to the axion resonant mode. Moreover, with this technique we have a complete knowledge of the signal extracted from the cavity, not only in magnitude but also in phase. This can be an interesting issue for future analysis where the axion phase is an important parameter.This work is part of the project PID2019-108122GB-C33 and the grant FPI BES-2017-079787 (under project FPA-2016-76978-C3-2-P), both funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe. JG acknowledges support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project).Peer reviewe

Thin Film (High Temperature) Superconducting Radiofrequency Cavities for the Search of Axion Dark Matter

5 pages, 6 figures. v2: minor updates after referee comments, matches published version in IEEEThe axion is a hypothetical particle which is a candidate for cold dark matter. Haloscope experiments directly search for these particles in strong magnetic fields with RF cavities as detectors. The Relic Axion Detector Exploratory Setup (RADES) at CERN in particular is searching for axion dark matter in a mass range above 30 $\mu$eV. The figure of merit of our detector depends linearly on the quality factor of the cavity and therefore we are researching the possibility of coating our cavities with different superconducting materials to increase the quality factor. Since the experiment operates in strong magnetic fields of 11 T and more, superconductors with high critical magnetic fields are necessary. Suitable materials for this application are for example REBa$_2$Cu$_3$O$_{7-x}$, Nb$_3$Sn or NbN. We designed a microwave cavity which resonates at around 9~GHz, with a geometry optimized to facilitate superconducting coating and designed to fit in the bore of available high-field accelerator magnets at CERN. Several prototypes of this cavity were coated with different superconducting materials, employing different coating techniques. These prototypes were characterized in strong magnetic fields at 4.2 K.This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under Grant Agreement No 730871 (ARIES-TNA). BD and JG acknowledge funding through the European Research Council under grant ERC-2018-StG-802836 (AxScale). We also acknowledge funding via the Spanish Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project PID2019- 108122GB-C33, and the grant FPI BES-2017-079787 (under project FPA2016-76978-C3-2-P). Furthermore we acknowledge support from SuMaTe RTI2018-095853-B-C21 from MICINN co-financed by the European Regional Development Fund, Center of Excellence award Severo Ochoa CEX2019- 000917-S and CERN under Grant FCCGOV-CC-0208 (KE4947/ATS).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

First results of the CAST-RADES haloscope search for axions at 34.67 μeV

We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ & 4 × 10−13 GeV−1 over a mass range of 34.6738μeV < ma < 34.6771μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavitiesWe wish to thank our colleagues at CERN, in particular Marc Thiebert from the coating lab, as well as the whole team of the CERN Central Cryogenic Laboratory for their support and advice in speci c aspects of the project. We thank Arefe Abghari for her contributions as the project's summer student during 2018. This work has been funded by the Spanish Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) under project FPA-2016-76978-C3-2-P and PID2019-108122GB-C33, and was supported by the CERN Doctoral Studentship programme. The research leading to these results has received funding from the European Research Council and BD, JG and SAC acknowledge support through the European Research Council under grant ERC-2018-StG-802836 (AxScale project). BD also acknowledges fruitful discussions at MIAPP supported by DFG under EXC-2094 { 390783311. IGI acknowledges also support from the European Research Council (ERC) under grant ERC-2017-AdG-788781 (IAXO+ project). JR has been supported by the Ramon y Cajal Fellowship 2012-10597, the grant PGC2018-095328-B-I00(FEDER/Agencia estatal de investigaci on) and FSE-GA2017-2019-E12/7R (Gobierno de Aragón/FEDER) (MINECO/FEDER), the EU through the ITN \Elusives" H2020-MSCA-ITN-2015/674896 and the Deutsche Forschungsgemeinschaft under grant SFB-1258 as a Mercator Fellow. CPG was supported by PROMETEO II/2014/050 of Generalitat Valenciana, FPA2014-57816-P of MINECO and by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreements 690575 and 674896. AM is supported by the European Research Council under Grant No. 742104. Part of this work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344

Workshop summary:Kaons@CERN 2023

Kaon physics is at a turning point – while the rare-kaon experiments NA62 and KOTO are in full swing, the end of their lifetime is approaching and the future experimental landscape needs to be defined. With HIKE, KOTO-II and LHCb-Phase-II on the table and under scrutiny, it is a very good moment in time to take stock and contemplate about the opportunities these experiments and theoretical developments provide for particle physics in the coming decade and beyond. This paper provides a compact summary of talks and discussions from the Kaons@CERN 2023 workshop, held in September 2023 at CERN

Expression of Interest: The Canfranc Axion Detection Experiment (CADEx)

Trabajo presentado al 29th Meeting of the LSC Scientific Committee, celebrado online del 30 de noviembre al 1 de diciembre de 2021.Peer reviewe

Measuring the hydrogen ground state hyperfine splitting through the pi1 and sigma1 transitions

Die ASACUSA Kollaboration arbeitet an einer Messung der Hyperfeinstruktur von Antiwasserstoff im Grundzustand (GSHS) mittels Rabi Spektroskopie, um die CPT Symmetrie zu testen. Die Hyperfeinstruktur von Wasserstoff wurde mit hoher Präzision bestimmt, weshalb der Vergleich mit diesem Wert für Antiwasserstoff auf einer absoluten Energieskala potenziell einer der genauesten Tests der CPT Symmetrie werden kann. Eine gute Charakterisierung des Spektrometers für dieses Experiment ist eine Voraussetzung, um die angestrebte Präzision zu erreichen. Der hohe Aufwand, der für die Produktion selbst von geringen Mengen von Antiwasserstoff erforderlich ist, verlangt nach alternativen Ansätzen für die Charakterisierung und rechtfertigt vorbereitende Messungen mit Materie. Aus diesem Grund hat das Stefan-Meyer-Institut (SMI) als Teil der ASACUSA Kollaboration ein Wassserstoffstrahlexperiment aufgebaut. Dieses wird dazu beitragen, dass der Zeitbedarf der Antiwasserstoffexperimente reduziert werden kann. Die Hauptkomponenten des Wasserstoffstrahlexperiments sind: Eine Quelle von gekühlten und modulierten atomaren Wasserstoff; ein Set von Permanentsextupolmagneten für die Polarisation des Strahls; ein Hohlraumresonator um die Hyperfeinübergänge zu treiben; McKeehan-artige Spulen um ein konstantes externes Magnetfeld zu generieren; ein weiteres Set von Permanentsextupolmagneten zwecks Analyse der Zustände; und ein Quadrupolmassenspectrometer als Wasserstoffdetektor. Im Rahmen der vorliegenden Arbeit wurde der Hohlraumresonator und Spulen-Aufbau verbessert, um die Untersuchung von zwei Hyperfeinübergängen zu ermöglichen. Während bereits im vorangegangen Aufbau der sigma1-Übergang zugänglich war, verlangt die Untersuchung des pi1-Übergangs eine verbesserte Homogenität des externen Magnetfeldes auf (sigmaB/|B|) < 1000 ppm. Deshalb wurden eine neue Magnetfeldabschirmung und McKeehan-artige Spulen konstruiert. Die Charakterisierung dieser neuen Bauteile ist ein wesentlicher Bestandteil dieser Arbeit und ein erreichter Wert von (sigmaB/|B|) ~ 590 ppm konnte verifiziert werden. Sowohl der sigma1- als auch der pi1-Übergang wurden zum ersten Mal unter Verwendung der neuen Abschirmung und Spulen vermessen. Von diesen Ergebnissen lässt sich die Hyperfeinstrukturaufspaltung von Wasserstoff im Grundzustand im feldfreien Fall ableiten. Die beiden Übergange erlauben unabhängig von einander die Extrapolation zum Nullfeld und alternativ können auch die Ergebnisse beider Übergänge beim gleichen Magnetfeldwert für eine Bestimmung benutzt werden. Die Extrapolationsmethode basierend auf dem pi1-Übergang wurde im Rahmen dieser Arbeit zum ersten Mal angewandt. Die Ergebnisse dieser Messungen sind alle innerhalb einer Standardabweichung in Übereinstimmung mit dem Literaturwert: nu0 = (1420405753 +- 8) Hz für die Methode mit beiden Übergängen beim gleichen externen Magnetfeld; nu0 = (1420405760 +- 34) Hz für die Extrapolation der Ergebnisse mittels pi1-Übergängen; und nu0 = (1420405767 +- 15) Hz für die Extrapolation der Ergebnisse mittels sigma1-Übergängen.The ASACUSA collaboration is aiming to measure the ground state hyperfine structure (GSHS) of antihydrogen to test the CPT symmetry in a Rabi like experiment. The GSHS of hydrogen is a very precisely known value. In addition the hyperfine splitting frequency is a small quantity, therefore a comparison with antihydrogen has the potential to yield one of the most precise tests of the CPT symmetry on an absolute energy scale. A good characterization of the experiment's spectrometry is a premise to achieve a high precision. The high cost and the low production rates of antihydrogen require alternative methods for this characterization and justify the use of matter for such preparations. For this reason the Stefan Meyer Institute (SMI) as part of the ASACUSA collaboration constructed a hydrogen beam experiment. This will help to shorten the time frame needed for the antihydrogen measurements. The main components of the hydrogen-beam setup are: a source of cold, modulated atomic hydrogen, a set of permanent sextupoles for polarization, a cavity to induce the spin flips, McKeehan-like coils to produce a homogeneous external magnetic field, another set of permanent sextupoles for state analysis and a quadropole mass spectrometer as detector. The same cavity is going to be used on the antihydrogen experiment and hence its characterization is highly relevant. Within the scope of this work, the cavity and coils assembly was modified to enable measurements of two transitions. While the sigma1-transition has been accessible by the previous setup as well, the pi1-transition requires an improved external magnetic field homogeneity of (sigmaB/|B|) < 1000 ppm. Therefore a new shielding as well as new McKeehan-like coils have been constructed. The characterization of these two new pieces of equipment is also part of the present work and a homogeneity of (sigmaB/|B|) ~ 590 ppm has been verified. Both pi1 and sigma1 transitions in hydrogen were measured for the first time using an upgraded setup. From these results the GSHS at zero magnetic field are calculated by extrapolation using the pi1 or sigma1 transitions separately and it will also be calculated using both transitions at the same static magnetic field. The results presented in this work of the GSHS using the pi1 extrapolation are the first results ever made using this method. The obtained GSHS result has the value of nu0 = (1420405753 +- 8) Hz using both transitions at the same static magnetic field. For the pi1 extrapolation, nu0 = (1420405760 +- 34) Hz. For the sigma1 extrapolation, nu0 = (1420405767 +- 15) Hz