Imaging Plates for Use with Synchrotron Radiation

This review summarizes the principles and performance characteristics of the imaging-plate (IP) X-ray area detector, which is based on the photo-stimulable phosphor BaF(Br,I):Eu²⁺, together with some of its applications at the Photon Factory. The photo-stimulable phosphor can temporarily store an X-ray image. The stored image is read out by measuring the intensity of luminescence, which is stimulated by an He-Ne laser beam scanning the phosphor surface. The IP has a spatial resolution of 170 μm (FWHM) with a pixel size of 100 × 100 μm and area sizes ranging from 127 × 127 to 201 × 400mm². The dynamic range is over l:10⁵. The detective quantum efficiency, which is a function of exposure level, is more than 80% for 8–20 keV X-rays at medium exposure levels. The background noise level is equivalent to less than 3 X-ray photons/pixel of 8 keV. The precision in intensity measurement is 0.5–1% at best. These performance characteristics of the IP depend largely on the performance of the IP readout system. Two applications of the IP to time-resolved measurements are discussed: one is based on a cinema method which achieves a 0.3 s time resolution for 40 exposures of size 127 × 127 mm², and the other uses the IP as a linear detector of length 200 mm with a 23 μs time resolution for a time period of 46 ms, based on the streak-camera method.