The X-ray spectroscopy telescope Athena has been designed to implement the science theme "the hot and energetic universe", selected by the European Space Agency as the second large mission of its Cosmic Vision program. X-IFU, one of the two interchangeable focal plane instruments of Athena, is a high resolution X-ray spectrometer made of a large array of Transition Edge Sensors. Two options are under consideration for the X-IFU microcalorimeters: Ti/Au bilayers or Mo/Au bilayers. Here we report on our efforts to develop Mo/Au-based TES. The TES are made of high quality superconducting Mo/Au bilayers fabricated at room temperature on low stress Si<sub>3</sub>N<sub>4</sub> membranes; Mo is deposited by RF magnetron sputtering and in-situ covered by a thin (15nm) Au layer deposited by DC sputtering; in a second step, the Au layer thickness is increased ex-situ by e-beam deposition, to obtain suitable resistance Rn and operation temperature values. Very sharp transitions (~few mK transition width) are obtained, with typically R<sub>n</sub>~25mΩ and T<sub>c</sub>~ 100-120mK for 65/215 bilayers. First simple TES designs are being tested. Also, Bi films several μm thick, intended to constitute the X-ray absorber, are fabricated by electrochemical deposition.
Athena is designed to implement the Hot and Energetic Universe science theme selected by the European Space Agency for the second large mission of its Cosmic Vision program. The Athena science payload consists of a large aperture high angular resolution X-ray optics (2 m2 at 1 keV) and twelve meters away, two interchangeable focal plane instruments: the X-ray Integral Field Unit (X-IFU) and the Wide Field Imager. The X-IFU is a cryogenic X-ray spectrometer, based on a large array of Transition Edge Sensors (TES), offering 2:5 eV spectral resolution, with ~5" pixels, over a field of view of 50 in diameter. In this paper, we present the X-IFU detector and readout electronics principles, some elements of the current design for the focal plane assembly and the cooling chain. We describe the current performance estimates, in terms of spectral resolution, effective area, particle background rejection and count rate capability. Finally, we emphasize on the technology developments necessary to meet the demanding requirements of the X-IFU, both for the sensor, readout electronics and cooling chain.
The EURECA (EURopean-JapanEse Calorimeter Array) project aims to demonstrate the science performance and
technological readiness of an imaging X-ray spectrometer based on a micro-calorimeter array for application in future
X-ray astronomy missions, like Constellation-X and XEUS. The prototype instrument consists of a 5 × 5 pixel array of
TES-based micro-calorimeters read out by by two SQUID-amplifier channels using frequency-domain-multiplexing
(FDM). The SQUID-amplifiers are linearized by digital base-band feedback. The detector array is cooled in a cryogenfree
cryostat consisting of a pulse tube cooler and a two stage ADR. A European-Japanese consortium designs,
fabricates, and tests this prototype instrument. This paper describes the instrument concept, and shows the design and
status of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, AC-bias sources, digital
Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray
energy resolution of 1.58 eV at 250 eV and 2.5 eV @ 5.9 keV for the read-out of one TES-pixel only. Next step is
deployment of FDM to read-out the full array. Full performance demonstration is expected mid 2009.
EURECA (EURopean-JapanEse Calorimeter Array) comprises a 5 x 5 pixel imaging TES-based micro-calorimeter
array read-out by SQUID-based frequency-domain-multiplexed electronics and cooled down by an adiabatic
demagnetization refrigerator. A European-Japanese consortium designs, fabricates, and tests this prototype instrument
with the aim to show within about 2 years technology readiness of a TES-based X-ray imaging micro-calorimeter array
in anticipation of future X-ray astronomy missions, like XEUS (ESA), Constellation-X (NASA), NEXT (JAXA), DIOS
(JAXA), ESTREMO (ASI), and NEW (Dutch-multinational). This paper describes the instrument concept, and shows
the design of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, flux-locked-loop
electronics, AC-bias sources, etc.