We propose a novel microwave kinetic inductance detector (MKID) named spiral-MKID typified by a rewound spiral strip structure suitable for terahertz applications. The superconducting rewound strip works as a high-Q half wavelength microwave resonator as well as a broadband terahertz antenna. The spiral-MKIDs fabricated with NbN films reveal loaded quality factors of the order of 104 at 3 K. NbN is one of the promising materials suitable for working on a convenient 4K-refrigerator. We also discuss the expected noise equivalent power of the optimized detector.
We compare a regenerator comprised of stacked wire meshes with that made of a honeycomb ceramic catalyst by measuring the acoustic fields in a tube containing the regenerator and air working gas at atmospheric pressure. The flow resistance of the wire-mesh regenerator increases in proportion to the velocity amplitude, whereas that of the honeycomb regenerator remains constant. An empirical equation of the flow resistance is proposed for the wire-mesh regenerator using an acoustic Reynolds number and ωτν (ω is the angular frequency of the acoustic waves and τνis the viscous relaxation time given using effective pore radius). The difference between these regenerators is also observed in the increased acoustic power achieved in the presence of axial temperature differences.