Status of the end-to-end demonstration readout chain for Athena/X-IFU

Abstract The X-ray Integral Field Unit (X-IFU) of the Athena observatory, scheduled for launch in the mid 2030's, will provide X-ray imaging spectroscopy data with unprecedented spectral and spatial resolution. The detection chain, based on a ~ 1.5 kilo-pixel array of transition edge sensors (TESs) cooled down to 55 mK, is under development by a large international collaboration. In order to perform an end-to-end demonstration of the X-IFU readout chain, a 50 mK test bench (Elsa), is being developed at IRAP in collaboration with CNES. Based on a commercial ADR cryostat, it includes a 1024-pixel TES array provided by NASA/GSFC with its associated cold readout chain provided by NIST. The validation of the performance of the system was performed using a NIST and NASA/GSFC laboratory warm readout chain. These laboratory electronics will be replaced step by step by the demonstration models of the space qualified electronics designed for the X-IFU: the digital readout electronics by IRAP and the warm front-end electronics by APC. We present here the status of the 50 mK test bench, its performance budget, and the demonstration of a prototype of a first element of the flight electronics.