Double peak phenomenon in superconducting tunnel junction x-ray detectors

Abstract

Tunneling of nonequilibrium quasiparticles excited by x-ray quanta in a nonsymmetric superconducting tunnel detector Low Temp.It has been normally observed that superconducting tunnel junction x-ray detectors produce a double peak originating from different absorption events in two electrodes. The double peak is associated with the dynamics of quasiparticles created by x-ray absorption events. In this study we have found that the double peak phenomenon depends on both bias voltage and magnetic history. On the events in the base and counterelectrodes the detector exhibits dissimilar signal-height versus bias-voltage characteristics, which suffer a large change when a small number of Abrikosov vortices corresponding to even a terrestrial magnetic field are frozen during cooling. These observations are explained by a multiple quasiparticle tunneling model with quasiparticle trapping in the vortices.

Superconducting Tunnel Junction Detectors for Analytical Sciences

“…4). The spectrum measured by the asymmetric STJ array detector is ideal with no double peaks originating from the absorption events in the top and bottom Nb electrodes and almost no artifact events due to wiring and contact hole structure [31], [32]. The STJ array detector was used to measure fluorescenceyield X-ray absorption fine structure (FY-XAFS) spectra of nitrogen dopant (300 ppm) in SiC at Beamline 11 of the High Energy Accelerator Research Organization, Photon Factory (KEK PF) [33].…”

Soft X-ray Detection Performance of Superconducting Tunnel Junction Arrays with Asymmetric Tunnel Junction Layer Structure

“…2,6) The spectral artifacts are double peak responses to monochromatic X-rays and artifact photon events in a low-energy region, and are henceforth called low-energy artifact events. 2,5,6,[18][19][20][21] Figure 1 shows a schematic diagram of spectral artifacts. The double peak response is caused by the X-ray absorption events in the top and bottom electrodes because conventional STJs have a symmetric tunnel junction layer structure and the thickness of their electrodes normally are $100 nm, which leads to the low absorption efficiency of the top electrode for soft X-rays.…”