Impact of the superconductors properties on the measurement sensitivity of resonant-based axion detectors

Abstract

Axions, hypothetical particles theorized to solve the strong CP-problem, are presently being considered as strong candidates as cold dark matter constituents. The signal power of resonant-based axion detectors, known as haloscopes, is directly proportional to their quality factor Q. In this paper, the impact of the use of superconductors in the performances of the haloscopes is studied by evaluating the obtainable Q. In particular, the surface resistance R s of NbTi, Nb 3 Sn, YBa 2 Cu 3 O 7−δ and FeSe 0.5 Te 0.5 is computed in the frequency, magnetic field and temperature ranges of interest, starting from the measured vortex motion complex resistivity and screening lengths of these materials. From R s the quality factor Q of a cylindrical haloscope with copper conical bases and superconductive lateral wall, operating with the TM 010 mode, is evaluated and used to perform a comparison of the performances of the different materials. Both YBa 2 Cu 3 O 7−δ and FeSe 0.5 Te 0.5 are shown to improve the measurement sensitivity by almost an order of magnitude with respect to a whole Cu cavity, while NbTi is shown to be suitable only at lower frequencies (< 10 GHz). Nb 3 Sn can give an intermediate improvement in the whole spectrum of interest.