Development of Superconducting Tunnel Junction X-ray Detector with High Absorption Yields Utilizing Silicon Pixel Absorbers

Abstract

A superconducting tunnel junction (STJ) array detector along with silicon pixel absorbers (STJ–SPA) is fabricated to achieve high detection efficiency at X-ray energies below 10 keV. The STJ pixels have dimensions of 100 $\upmu$m $\times$ 100 $\upmu$m and are composed of Nb–Al/AlO$_{X}$/Al–Nb thin layers. The SPAs are also 100 $\upmu$m $\times$ 100 $\upmu$m and have a depth of 400 $\upmu$m, and are isolated from each other by a deep trench with a depth of 350 $\upmu$m. The detection efficiency of the STJ–SPA exceeds 95 % at X-ray energies below 10 keV, and its energy resolution is 82 eV FWHM, as measured at the Si K$\upalpha$ line at 1740 eV. By means of the STJ–SPA detector, the X-ray absorption spectrum of the light element sulfur with a concentration of less than 0.1 wt% in a soda-lime glass sample was successfully acquired.