Performance of the SRON Ti/Au Transition Edge Sensor X-ray Calorimeters

TL;DR

This paper reviews the development and performance of SRON's Ti/Au transition-edge sensor X-ray calorimeters, highlighting their excellent energy resolution, tunability, and readiness for deployment in ESA's Athena X-ray observatory.

Contribution

It presents a comprehensive overview of the properties, fabrication, and optimization of Ti/Au TES arrays, advancing their application for high-resolution X-ray spectroscopy in space missions.

Findings

Energy resolution below 1.8 eV at 5.9 keV

Precise control of detector properties like resistance and critical temperature

Successful tuning for different read-out schemes

Abstract

In the early 2030s, ESAs new X-ray observatory, Athena, is scheduled to be launched. It will carry two main instruments, one of which is the X-ray Integral Field Unit (X-IFU), an X-ray imaging spectrometer, which will consist of an array of several thousand transition-edge sensors (TESs) with a proposed energy resolution of 2.5 eV for photon energies up to 7 keV. At SRON we develop the backup TES array based on Ti/Au bilayers with a transition temperature just below 100 mK. In this contribution we will give a broad overview of the properties and capabilities of these state-of-the-art detectors. Over the years we have fabricated and studied a large number of detectors with various geometries, providing us with a good understanding of how to precisely control the properties of our detectors. We are able to accurately vary the most important detector properties, such as the normal resistance, thermal conductance and critical temperature. This allows us to finely tune our detectors to meet the demands of various applications. The detectors have demonstrated excellent energy resolutions of below 1.8 eV for 5.9 keV X-rays. By tuning the properties of the devices, they can be optimally matched to various read-out schemes using both AC and DC biasing. The next step is to increase the size of our TES arrays from our current kilo-pixel arrays towards the full-sized array for X-IFU.