X-ray energy spectrum measurements by an annular superconducting tunnel junction with trapped magnetic flux quanta

Abstract

We report on the Fe55 x-ray pulse height spectrum of an annular superconducting tunnel junction (STJ) collected without an external magnetic field. An energy resolution of 100eV was obtained for the Kα line of the top electrode. The Josephson critical current and Fiske resonances were suppressed by the presence of trapped magnetic flux quanta which created a persistent current and self-generated magnetic field. The obtained energy resolution and the stability of the trapped magnetic flux under irradiation demonstrate the capability of an annular STJ device with trapped flux quanta to detect radiation without using the external magnetic field that is required in the conventional detection scheme.

New Fluxon Resonant Mechanism in Annular Josephson Tunnel Structures

“…These devices have been considered recently in connection with a number of fundamental physics experiments: the macroscopic quantum tunneling of a single superconducting vortex in real space [10], the quantum generation of fluxonantifluxon (F-AF) pairs [11] in view of the potential implementation of vortex qubit circuits based on annular Josephson structures [12]. They have been proposed as advanced radiation cryodetectors [13], as devices to detect effects of the geometric Berry phase on the vortex dynamics [14], and even for testing, in laboratory, quantum field theory models of the early Universe [15]. In long annular junctions FS and ZFS appear at the asymptotic voltage positions V n n c 0 =L, where n is an integer number, L is the length of the circumference of the junction, c is the velocity of light in the junction, and 0 is the flux quantum.…”