High-sensitivity CCD-based X-ray detector

The detector is designed for imaging measurements requiring relatively high sensitivity and high spatial resolution. The detector can discriminate single X-ray photons, yet has the wide dynamic range (∼10000:1) associated with integrating detectors. A GdO₂S₂ phosphor screen converts the incoming X-ray image into an optical image. The optical image is coupled (without demagnification) to the CCD image sensor using a fiber optic faceplate. The CCD (Philips Semiconductors) has an area of 4.9 × 8.6 cm with 4000 × 7000 12 µm pixels. A single 12 keV X-ray photon produces a signal of 100 e⁻. With 2 × 2 pixel binning, the total noise per 24 µm pixel in a 100 s image is ∼30 e⁻, the detective quantum efficiency is >0.6 at 1 X-ray photon per pixel, and the full image can be read out in <4 s. The spatial resolution is 50 µm. The CCD readout system is fully computer-controlled, allowing flexible operation in time-resolved experiments. The detector has been characterized using visible-light images, X-ray images and time-resolved muscle diffraction measurements.