The x-ray mirrors for the EXIST/SXI telescope

The Energetic X-ray Imaging Survey Telescope (EXIST) will continuously survey the full sky in scanning mode for 2- years followed by a 3-years pointing phase. The mission includes three instruments: a High Energy coded mask Telescope; a 1.1m aperture optical-IR Telescope; and a Soft X-ray Imager (SXI), sensitive in the 0.1-10 keV band. SXI is proposed as a contribution of ASI-Italy, fully developed by Italian institutes. Here we will present the optical and mechanical design of the SXI mirror module, that includes also a pre-collimator and a magnetic diverter to ensure a low background on the detector. In particular we will describe the mirror module characteristics in term of effective area, imaging capability, thermal requirement and mechanical properties. The current optical design foresees 26 shells providing an effective area comparable to one XMM-Newton mirror module up to 3 keV. The realization of these shells is based on the well-proven Nickel replication-process technology.