High Aspect Ratio Transition Edge Sensors for X-ray Spectrometry

TL;DR

This paper characterizes high aspect ratio transition edge sensors (TES) for X-ray spectrometry, demonstrating that optimized geometries can achieve excellent energy resolution suitable for space observatories.

Contribution

It provides a comprehensive analysis of various high aspect ratio TES geometries, showing their potential for high-performance X-ray detection under AC bias.

Findings

High aspect ratio TESs achieve energy resolutions around 1.63 eV at 5.9 keV.

Properly tuned critical temperatures (~90 mK) are crucial for optimal performance.

AC-biased TESs can match the performance of traditional DC-biased devices.

Abstract

We are developing large TES arrays in combination with FDM readout for the next generation of X-ray space observatories. For operation under AC-bias, the TESs have to be carefully designed and optimized. In particular, the use of high aspect ratio devices will help to mitigate non-ideal behaviour due to the weak-link effect. In this paper, we present a full characterization of a TES array containing five different device geometries, with aspect ratios (width:length) ranging from 1:2 up to 1:6. The complex impedance of all geometries is measured in different bias configurations to study the evolution of the small-signal limit superconducting transition parameters, as well as the excess noise. We show that high aspect ratio devices with properly tuned critical temperatures (around 90 mK) can achieve excellent energy resolution, with an array average of 2.03 +- 0.17 eV at 5.9 keV and a best achieved resolution of 1.63 +- 0.17 eV. This demonstrates that AC-biased TESs can achieve a very competitive performance compared to DC-biased TESs. The results have motivated a push to even more extreme device geometries currently in development.