COLD - The CryOgenic Laboratory for Detectors of LNF. From axion searches to quantum technologies
(Istituto Nazionale di Fisica Nucleare)
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COLD is a cryogenic laboratory born to develop high-sensitivity low-noise detectors for light dark-matter searches, thanks to the skills present at LNF in cryogenics, radiofrequency, superconductivity and particle physics. The laboratory is equipped with dilution refrigerators, LHe cryostats, magnets up to 9T, low noise electronics and radiofrequency instruments up to 20 GHz. The lab hosts one of the two haloscopes, a type of axion detector, of the QUAX experiment, the other being at the Laboratori Nazionali di Legnaro of INFN. Axions are hypothetical particles theorized to solve the so-called Strong-CP problem that could pervade our galaxy manifesting themselves only through their gravitational interaction. A Haloscopes is a cryogenic antenna able to resonantly convert the axions into electromagnetic signals. The extremly weak power generated by these conversions poses one of the greatest challenge to axion experiments that can be addressed only through the use of recently developed quantum technologies such as quantum amplifiers, or better, superconducting single microwave-photon detectors. This led us to undertake the development of sensors based on Josephson junctions and superconducting qubits. In parallel, we carried out the study of superconducting and dielectric resonant-cavities able to operate in strong magnetic-field while keeping a high quality-factor needed to enhance the axion signal. A further development of the COLD lab activity was the conceptual design of the KLASH experiment, now evolved into FLASH, a large valume haloscope to be hosted inside the superconducting magnet of the FINUDA experiment. Beside axions this detector would be sensitive to dark photons and high-frequency gravitational-waves.