Interaction of X-Ray Photons With Abrikosov Vortices in Josephson Tunnel Junctions With a Bulk Niobium Base Electrode

Abstract

γ-rays can be efficiently detected by superconductor devices exploiting the interaction of single γ-ray photons with Abrikosov vortices. In order to prove the feasibility of this novel detection mechanism, Josephson tunnel junctions were fabricated on bulk polycrystalline niobium base electrodes consisting of 0.3-mm-thick niobium foils, and investigated under <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">55</sup> Fe X-ray. The fabrication process is discussed with a particular attention to the treatment of the surface of the niobium foil. Niobium-bulk/Al/AlO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> /Al/niobium Josephson junctions with different circular areas were tested at the temperature T = 4.2 K and their current-voltage and Josephson critical current dependence on parallel magnetic field were characterized. The experimental magnetic field dependences of the Josephson critical current have been well fitted by the Airy diffraction pattern. Depinning of Abrikosov vortices under X-ray photons has been observed by means of variation of the magnetic dependence of the Josephson critical current.