The wide field imager for the international X-ray observatory

The large collecting area of the X-ray optics on the International X-ray Observatory (IXO), their good angular resolution, the wide bandwidth of X-ray energies and the high radiation tolerance required for the X-ray detectors in the focal plane have stimulated a new development of devices which unify all those science driven specifications in one single detector. The concept of a monolithic, back-illuminated silicon active pixel sensor (APS) based on the DEPFET structure is proposed for the IXO mission, being a fully depleted, back-illuminated 450 μm thick detector with a physical size of about 10 × 10 cm2 corresponding to the 18 arcmin field of view. The backside will be covered with an integrated optical light and UV-filter. Corresponding to the 5 arcsec angular resolution of the X-ray optics, 100 x 100 cm2 large pixels in a format of approximately 1024 x 1024 are envisaged, matching the point spread function of approximately 500 μm HEW of the optics. The energy range from 100 eV to 15 keV is achieved by an ultra thin radiation entrance window for the low energies and 450 μm depleted silicon thickness for higher energies. The fast readout of 1.000 full frames per second is realized by a dedicated analog CMOS front end amplifier IC. The detector device is intrinsically radiation hard. The leakage current from the bulk damage is controlled through the operation temperature around -60 °C and by the high readout speed. Results of various prototype measurements will be shown.