Characterization of a large-format x-ray microcalorimeter array based on transition edge sensors

Abstract

We report on the development and cryogenic tests of a full-sized array of Transition Edge Sensors (TESs) designed for the X-ray Integral Field Unit (X-IFU). The wafer, comprising a fully-wired array of over 1500 high-performance TES microcalorimeters, was fabricated to meet the stringent requirements of the X-IFU. The quality of the full-sized array is assessed by the study of representative smaller arrays on pop-out diagnostic chips located near the mean array on the same wafer. Characterization is performed using a dedicated DC-biased setup featuring PTB SQUIDs and SRON lithographically-defined shunt resistors and Nyquist inductors. This setup enables the characterization of up to 14 detectors in a single cooling run. Comprehensive measurements at milliKelvin temperatures were conducted to evaluate the detector uniformity, transition parameters, noise characteristics, and energy resolution. Our results demonstrate excellent uniformity over all devices tested on the different diagnostic chips. These findings demonstrate the robustness of the SRON TES technology, and raise confidence in our capability of delivering a full-fledged detector array that fulfils all requirements for X-IFU if the need arises. Our results also demonstrate the readiness of the detector technology for other laboratory applications or future X-ray observatories.