Performance Characterization of Microwave-Multiplexed Transition Edge Sensors for X-Ray Synchrotron Applications

State of the art energy-resolving detectors for synchrotrons are required to take full advantage of the capabilities of these facilities. Most spectroscopic applications at x-ray beam-lines require energy resolutions of the order of E/E>1000 and high detection efficiencies, which is beyond the capabilities of both semiconducting detectors and wavelength-dispersive spectrometers. Transition Edge Sensors represent the best candidates for this role by providing high-energy resolution with non-dispersive operation, and with much higher photon-collection efficiency. Recently a novel readout scheme for TESs based on microwave resonators has been introduced by NIST that allows array scalability to high pixel counts. In this work, we describe its application to TESs for x-ray, with particular attention to the optimization of the readout settings. Parameters such noise, linearity and sampling rate represent the benchmarks of this characterization.