Evaluation of an X-ray imaging detector based on a CMOS camera with logarithmic response

An X-ray imaging detector made of an X-ray image intensifier coupled to a non-integrating logarithmic CMOS camera is evaluated. Linearly scaled X-ray images over six decades of dynamic range are obtained after calibration of the detector response, representing a gain of more than one order of magnitude compared with state-of-the-art CCD-based X-ray detectors. The system provides images which are free of smearing or blooming at maximum exposure without mechanical shuttering. Other characteristics are a sensitive area of 123×61 mm, a pixel size of 240 μm, a noise-limited detection threshold of 25 photons/pixels/s at 18 keV. In X-ray diffraction images the effective measuring range is better than 104 for neighbouring diffraction spots, whereas the full 106 range is available for remote spots. At reduced dynamic range a frame rate of 60 images/s can be achieved. The performed evaluation demonstrates the interest of this detector concept as a possible alternative to CCD-based detectors for various applications at synchrotron sources requiring an extended dynamic range and subsecond duty cycle requirements.