The enhanced X-ray Timing and Polarimetry mission (eXTP) is a Chinese science satellite with a strong European participation. The planned launch date of the mission is earlier than 2025. eXTP’s scientific purpose is to study the state of matter under extreme conditions of density, gravity and magnetism. Primary goals are the determination of the equation of state of matter at supra-nuclear density, the measurement of QED effects in highly magnetized stars, and the study of accretion in the strong-field regime of gravity. Primary targets include isolated and binary neutron stars, strong magnetic field systems like magnetars, and stellar-mass and supermassive black holes.

The payload consist of a unique and unprecedented suite of state-of-the-art scientific instruments enabling for the first time ever the simultaneous spectral-timing-polarimetry studies of cosmic sources in the energy range from 0.5-30 keV. The payload consist of four complementary components (Fehler: Verweis nicht gefunden):

  • the Spectroscopic Focusing Array (SFA): a set of eleven identical X-ray telescopes operating in the 0.5‑10 keV energy band with a field-of-view (FoV) of 12 arcmin each and a total effective area of 0.8 m2 and 0.5 m2 at 2 keV and 6 keV respectively. The telescopes are equipped with Silicon Drift Detectors offering < 180 eV spectral resolution.

  • the Large Area Detector (LAD): a deployable set of 640 Silicon Drift Detectors, achieving a total effective area of 3.4 m2 between 6 and 10 keV. The operational energy range is 2‑30 keV and the achievable spectral resolution better than 250 eV. LAD is a non-imaging instrument, with the FoV limited to <1° FWHM by the usage of compact capillary plates. 

  • the Polarimetry Focusing Array (PFA): a set of four X-ray telescopes, achieving a total effective area of 900 cm2 at 2 keV, equipped with imaging gas pixel photoelectric polarimeters. The FoV of each telescope is 12 arcmin and the operating energy range is 2‑10 keV.

  • the Wide Field Monitor (WFM): a set of three coded mask wide field units, equipped with position-sensitive Silicon Drift Detectors, covering almost a third of the sky sphere and operating in the energy range 2-50 keV.

The detector part of the SFA instrument is under the responsibility of the Max-Planck-Institute for Extraterrestrial Physics (MPE). SFA will record the light curve of time-variable sources in the energy band from 500 eV to 10 keV. For this purpose, the sensor will be placed out of the focal plane and does not need position resolution but excellent energy resolution, high rate capability, and large area coverage. The baseline detector for the SFA is a multi-cell Silicon Drift Detector (SDD). The SDD concept combines a large area and a small value of the readout capacitance. To take the full advantage of the small capacitance the first stage of the amplifying electronics is integrated on the SDD chip. For the signal acquisition the SDD output lines will be connected to readout ASICs developed by the Politecnico di Milano. The system will deliver the spectral information of the observed source with an energy resolution better than 180 eV (FWHM at 6 keV) and a time resolution better of 10 µsec.

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