IXPE DU-FM ions-UV filters characterization

IXPE (Imaging X-ray Polarimetry Explorer) is a NASA SMEX in a partnership with ASI. The focal plane Detector Units (DUs) and the Detector Service Unit (DSU) were developed by the Italian research Institutes INAF-IAPS and INFN and were manufactured by OHB-I. IXPE will investigate X-ray polarimetry in the 2-8 keV energy band. The payload comprises three identical telescopes, each composed of a mirror and a detector unit with an X-ray polarimeter based on the Gas Pixel Detector (GPD). A stray-light collimator (SLC) is mounted on the top of the DU to shield the GPD from background X-rays not coming from the optics. At the bottom of the SLC, an ions-UV filter is mounted to reduce the thermal load and to prevent ions and UV from entering the DU. The ions-UV filters consist mainly of 1 um LUXFilm (based on polyimide). During on-ground calibration activities of the IXPE DUs, X-ray transparency of DU-FM ions-UV filters was measured with monochromatic X-ray at 2.7 keV and 6.4 keV at INAF-IAPS.