Design of a 8×14 pixel Ta-based STJ X-ray detector array

We are developing high-resolution high-speed superconducting tunnel junction (STJ) detectors for synchrotron science to study metal speciation by fluorescence-detected X-ray absorption spectroscopy. The sensitivity of our current 36-pixel Nb–Al-based STJ spectrometer can be improved by replacing the Nb absorber film with higher-efficiency Ta and by increasing the array size. In addition, an improved device layout can reduce spectral artifacts that limit the peak-to-background ratio and thus the sensitivity for analyzing dilute samples. We present a detailed analysis of the spectral artifacts in our current STJs and discuss the considerations to reduce them in the next-generation 8×14 Ta-based STJ arrays, as well as the trade-offs between energy resolution, efficiency, speed and spectral purity.