  The ATHENA X-ray Observatory-IXO is a planned multinational orbiting X-ray
observatory with a focal length of 11.5m. ATHENA aims to perform pointed
observations in an energy range from 0.1 keV to 15 keV with high sensitivity.
For high spatial and timing resolution imaging and spectroscopic observations
the 640x640 pixel^2 large DePFET-technology based Wide field Imager (WFI) focal
plane detector, providing a field of view of 18 arcsec will be the main
detector. Based on the actual mechanics, thermal and shielding design we
present estimates for the WFI cosmic ray induced background obtained by the use
of Monte-Carlo simulations and possible background reduction measures.
