Performance and uniformity of a kilo-pixel array of Ti/Au transition-edge sensor microcalorimeters.

Abstract

Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ray space observatories. These arrays are required to achieve an energy resolution ΔE < 3eV full width at half maximum (FWHM) in the soft x-ray energy range. We are currently developing x-ray microcalorimeter arrays for use in the future laboratory and space-based x-ray astrophysics experiments and ground-based spectrometers. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with 140 × 30 μm2 Ti/Au TESs with the Au x-ray absorber. We report on extensive measurements on 60 pixels in order to show the uniformity of our large TES array. The averaged critical temperature is Tc = 89.5 ± 0.5 mK, and the variation across the array (∼1cm) is less than 1.5 mK. We found a large region of detector's bias points between 20% and 40% of the normal-state resistance where the energy resolution is constantly lower than 3eV. In particular, results show a summed x-ray spectral resolution ΔEFWHM = 2.50 ± 0.04eV at a photon energy of 5.9 keV, measured in a single-pixel mode using a frequency domain multiplexing readout system developed at SRON/VTT at bias frequencies ranging from 1MHz to 5MHz. Moreover, we compare the logarithmic resistance sensitivity with respect to temperature and current (α and β, respectively) and their correlation with the detector's noise parameter M, showing a homogeneous behavior for all the measured pixels in the array.