Background limited superconducting quantum detector for submillimeter astronomy

Abstract

e extend the concept of the superconducting quantum counter in order to develop a new quantum detector for submillimeter astronomy. The detector exploits a cumulative detection mechanism, in which the response appears due to successive formation of the normal spot and a resistive domain in a narrow strip carrying sub-critical supercurrent. The intrinsic recovery time of the counter is partly determined by diffusion of nonequilibrium electrons and, thus, depends on the energy of detected photons. Depending on the superconducting material used and operation conditions, such detector may have cut-off wavelengths for the single-photon regime ranging from terahertz waves to visible light and simultaneously provide a moderate energy resolution. We simulated performance of the background-limited submillimeter direct detector from Ti having the 100-micrometer cut-off wavelength, low dark count rate and intrinsic 10-21 W Hz-1/2 noise equivalent power for 4-K background radiation. We present first results obtained with a detector prototype fabricated from ultra-thin Nb film.