Development of high-Q superconducting resonators for use as kinetic inductance sensing elements

One of the greatest challenges in the development of very sensitive radiation detectors is the fabrication of a large detector array. Within this context we have started the development of Kinetic Inductance Detectors. The heart of each detector consists of a high-Q superconducting quarter wavelength microwave resonator. As a result, it is easy to multiplex the readout by frequency division multiplexing. We describe our initial experiments with these resonators, made on 20×4 mm high-purity Si chips using 100 nm Nb films. We measure the Q factors of several resonators using a vector network analyzer and find Q factors up to 90.000, limited by the intrinsic quality of the Nb resonator.