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 < 3 eV 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 (∼1 cm) 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 3 eV. In particular, results show a summed x-ray spectral resolution ΔEFWHM = 2.50 ± 0.04 eV 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 1 MHz to 5 MHz. 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.

A Review of X-ray Microcalorimeters Based on Superconducting Transition Edge Sensors for Astrophysics and Particle Physics

“…The geometry of these devices is rectangular with dimensions (length× width) 100 × 20 , 120 × 20, 140 × 30, 80 × 20, and 80 × 40 µm 2 , which correspond to aspect ratios ranging from 2:1 up to 6:1. The results on the characterization and uniformity of a kilo-pixels array of 140 × 30 µm 2 is reported in [121,122]. More details on the TES design and fabrication are given in [89] and in Section 3.…”

TiAu TES 32$\times$32 pixel array: uniformity, thermal crosstalk and performance at different X-ray energies

“…We can consider the averaged T c = 89.5±0.4 mK. This dispersion around the mean value might be explained considering some of the critical aspects in the whole fabrication process [9]. We have measured the energy resolution by exposing the TES array to a standard 55 Fe source, providing Mn-Kα X-rays at an energy of 5.9 keV with a count rate of approximately 1 count per second (cps) per pixel.…”

“…We have measured the energy resolution by exposing the TES array to a standard 55 Fe source, providing Mn-Kα X-rays at an energy of 5.9 keV with a count rate of approximately 1 count per second (cps) per pixel. More information about the setup are reported in this recent work [9]. Typically, we collect about 5000 X-ray events for each spectrum to get a statistical error of about 0.15 -0.18 eV for the reported energy resolution.…”

“…Square pixels [3], [5] and high aspect ratio devices [6], [7] have been fully characterised using our frequency domain multiplexing (FDM) readout system and a preliminary comparison of the performance, between same devices biased under AC and DC, have been also investigated [8]. Lately, uniformity of a 32×32 pixels array have been extensively studied and the results have been widely reported [9]. However, besides the homogeneity, many other aspects play a crucial role in fabrication and in the delivery of large arrays.…”

Simulation Method for Investigating the Use of Transition-Edge Sensors as Spectroscopic Electron Detectors

“…As such, they are a potential candidate for a range of applications, including XPS. Large arrays of TESs can be fabricated lithographically and operated simultaneously, increasing the available measurement rate without compromising energy resolution; multiplexed arrays numbering thousands of TESs are currently being developed for spacebased astronomical X-ray measurements [1,2]. TESs are also being developed for infrared, optical and UV spectroscopy in the context of emerging quantum experiments and technologies [3].…”