Frequency-domain multiplexing (FDM) is the baseline readout system for the X-ray Integral Field Unit on board the Athena mission. Under the FDM scheme, TESs are coupled to a passive LC filter and ...biased with alternating current (AC bias) at MHz frequencies. Using high-quality-factor LC filters and room-temperature electronics developed at SRON and low-noise two-stage SQUID amplifiers provided by VTT, we have recently demonstrated good performance with the FDM readout of Mo/Au TES calorimeters with Au/Bi absorbers. We have achieved a performance requested for the demonstration model with the single-pixel AC bias ( ΔE = 1.8 eV ) and nine-pixel multiplexing ( ΔE = 2.6 eV ) modes. We have also demonstrated 14-pixel multiplexing with an average energy resolution of 3.3 eV, which is limited by nonfundamental issues related to FDM readout in our laboratory setup.
We are developing kilo-pixel arrays of transition-edge sensors (TESs) for the X-ray Integral Field Unit on ESA's (European Space Agency's) Athena observatory. Previous measurements of AC-biased Mo/Au ...TESs have highlighted a frequency-dependent loss mechanism that results in broader transitions and worse spectral performance compared to the same devices measured under DC (Direct Current) bias. In order to better understand the nature of this loss, we are now studying TES pixels in different geometric configurations. We present measurements on devices of different sizes and with different metal features used for noise mitigation and X-ray absorption. Our results show how the loss mechanism is strongly dependent upon the amount of metal in close proximity to the sensor and can be attributed to induced eddy current coupling to these features. We present a finite element model that successfully reproduces the magnitude and geometry dependence of the losses. Using this model, we present mitigation strategies that should reduce the losses to an acceptable level.
CNES (French Space Agency) is in charge of the development of the X-ray Integral Field Unit (X-IFU) instrument for Athena, the high resolution X-ray spectrometer of the ESA Athena X-ray Observatory. ...X-IFU will deliver spectra from 0.2 to 12 keV with a spectral resolution in the range of 2.5 eV up to 7 keV on a 5′′ pixels, with a field of view > 4′ equivalent diameter. The main sensor array detection chain is a key part of the instrument, being by far the main contributor to its performance. It involves major partners: NASA GFSC, NIST, SRON, VTT, APC, and IRAP. The cryo-harness interconnecting the Focal Plane Assembly cold interface to the Warm Front End Electronics is under CNES responsibility. The different technical solutions are the loom technology and the shielded twisted pair technology. Characterizations have been performed on breadboards to assess the crosstalk performances for each solution. The results of these analysis are a driver to perform the trade-off between the available cryo-harness technologies.
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