The QCD axion has emerged in the last decade as a prominent candidate to the composition of the cold dark matter. The existence of an axion-photon coupling proportional to the magnetic field intensity has stimulated several experimental efforts towards its revelation, most based on the haloscope design introduced by P. Sikivie. The core component of this latter detector is a microwave cavity coupled to a receiver chain, allowing to exploit the coherence of the axion field to resonantly enhance and then amplify the converted signal. However, due to the scaling with frequency of parameters such as cavity volume and quality factor, this approach has diminishing returns moving towards high frequencies. In this dissertation, I detail the development process of a novel normo-conductive, dielectrically-loaded cavity resonating at 10.4\,GHz. Exploiting the $\mathbf{TM_{030}}$ resonant mode, it is capable of reaching quality factors of $\sim10^7$ under a 8\,T magnetic field, overcoming the axion quality factor for the first time in an axion search. I also present the setup, calibration, analysis procedure and the results obtained from the QUAX 2021 axion search run. A $90\%$ C.L. upper limit on the axion-photon coupling $g_{a\gamma\gamma}$ was set in the interval [10.35327;10.35354]\,GHz, with peak sensitivity of $g_{a\gamma\gamma}&gt;5.6\times10^{-14}$ GeV$^{-1}$. Due to the very high receiver noise temperature of this setup, an improvement in sensitivity of a factor of 10 over the current result is expected in the near future thanks to the implementation of several improvements.

Di Vora, R. (2022). High frequency Dark Matter axion search with very high-quality factor dielectric resonators in the QUAX-aγ experiment.

### High frequency Dark Matter axion search with very high-quality factor dielectric resonators in the QUAX-aγ experiment

#### Abstract

The QCD axion has emerged in the last decade as a prominent candidate to the composition of the cold dark matter. The existence of an axion-photon coupling proportional to the magnetic field intensity has stimulated several experimental efforts towards its revelation, most based on the haloscope design introduced by P. Sikivie. The core component of this latter detector is a microwave cavity coupled to a receiver chain, allowing to exploit the coherence of the axion field to resonantly enhance and then amplify the converted signal. However, due to the scaling with frequency of parameters such as cavity volume and quality factor, this approach has diminishing returns moving towards high frequencies. In this dissertation, I detail the development process of a novel normo-conductive, dielectrically-loaded cavity resonating at 10.4\,GHz. Exploiting the $\mathbf{TM_{030}}$ resonant mode, it is capable of reaching quality factors of $\sim10^7$ under a 8\,T magnetic field, overcoming the axion quality factor for the first time in an axion search. I also present the setup, calibration, analysis procedure and the results obtained from the QUAX 2021 axion search run. A $90\%$ C.L. upper limit on the axion-photon coupling $g_{a\gamma\gamma}$ was set in the interval [10.35327;10.35354]\,GHz, with peak sensitivity of $g_{a\gamma\gamma}>5.6\times10^{-14}$ GeV$^{-1}$. Due to the very high receiver noise temperature of this setup, an improvement in sensitivity of a factor of 10 over the current result is expected in the near future thanks to the implementation of several improvements.
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Di Vora, R. (2022). High frequency Dark Matter axion search with very high-quality factor dielectric resonators in the QUAX-aγ experiment.
Di Vora, Raffaele
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11365/1213654