RESUMEN
Searches for dark matter axions involve the use of microwave resonant cavities operating in a strong magnetic field. Detector sensitivity is directly related to the cavity quality factor, which is limited, until recently, to the use of non-superconducting metals by the presence of the external magnetic field. In this paper, we present a cavity of novel design whose quality factor is not affected by a magnetic field. It is based on a photonic structure by the use of sapphire rods. The quality factor at cryogenic temperature is in excess of 5 × 105 for a selected mode.
RESUMEN
A ferromagnetic axion haloscope searches for dark matter in the form of axions by exploiting their interaction with electronic spins. It is composed of an axion-to-electromagnetic field transducer coupled to a sensitive rf detector. The former is a photon-magnon hybrid system, and the latter is based on a quantum-limited Josephson parametric amplifier. The hybrid system consists of ten 2.1 mm diameter yttrium iron garnet spheres coupled to a single microwave cavity mode by means of a static magnetic field. Our setup is the most sensitive rf spin magnetometer ever realized. The minimum detectable field is 5.5×10^{-19} T with 9 h integration time, corresponding to a limit on the axion-electron coupling constant g_{aee}≤1.7×10^{-11} at 95% C.L. The scientific run of our haloscope resulted in the best limit on dark matter axions to electron coupling constant in a frequency span of about 120 MHz, corresponding to the axion-mass range 42.4-43.1 µeV. This is also the first apparatus to perform a wide axion-mass scanning by only changing the static magnetic field.
RESUMEN
We report on the resonant Fabry Perot cavity of the PVLAS (Polarization of the Vacuum with LASer) experiment operating at λ = 1064 nm with a record decay time of 2.7 ms, a factor more than two larger than any previously reported optical resonator. This corresponds to a coherence length of 8.1 · 10(5) m. The cavity length is 3.303 m, and the resulting finesse is 770,000.
