X-Ray Induced Secondary Particle Counting With Thin NbTiN Nanowire Superconducting Detector

Abstract

We characterized the performance of abiased superconducting nanowire to detect X-ray photons. The device, made of a 10\xa0nm thin NbTiN film and fabricated on a dielectric substrate (<inline-formula><tex-math notation= LaTeX >$SiO_{2}$</tex-math></inline-formula>, Nb<inline-formula><tex-math notation= LaTeX >$_{3}$</tex-math></inline-formula>O<inline-formula><tex-math notation= LaTeX >$_{5}$</tex-math></inline-formula>) detected 1000 times larger signal than anticipated from direct X-ray absorption. We attributed this effect to X-ray induced generation of secondary particles in the substrate. The enhancement corresponds to an increase in the flux by the factor of 3.6, relative to a state-of-the-art commercial X-ray silicon drift detector. The detector exhibited 8.25\xa0ns temporal recovery time and 82\xa0ps timing resolution, measured using optical photons. Our results emphasize the importance of the substrate in superconducting X-ray single photon detectors.