This article attempts to describe the recent trends of X-ray detectors in synchrotron radiation science in the light of not only the advance but also the stagnation of which are seriously dependent upon the current semiconductor technology.

  The Imaging Plate (IP) has the excellent properties of the large active area size and the wide dynamic range, however the long readout time of the stored image is becoming the greatest drawback at synchrotron radiation facility. To overcome the difficulty, a high-speed IP detector, which can readout a large number of 400 x 400 mm² IPs successively less than 60 seconds / IP has been designed and developed for protein crystallography.

SPring-8 BL40XU is designed to use high flux X-ray for small angle X-ray scattering and multi purpose. The flux at the experimental hutch is about 1×10¹⁵ photons/sec at 12.4 KeV, which is larger 2～3 figures than other beamlines at SPring-8. To utilize the high flux X-ray efficiently, new high-speed detector is needed. Therefore, a high frame rate CCD camera C7770 (Hamamatsu) and a new 6-inch X-ray image intensifier V5445P (Hamamatsu) were developed for BL40XU. The CCD camera has three CCD chips to increase the readout speed. Three identical images are created by a prism system in the CCD camera and projected onto the three chips. The pixel number of the CCD is 640×480 and the frame rate is 291 frames/sec. Reduction of the number of horizontal lines leads to a faster frame rate up to a few thousands. The combination of the CCD and with an X-ray shutter also leads to faster discrete data acquisition.

  High spatial resolution X-ray detector is a key technology for X-ray micro-imaging. In SPring-8, visible light conversion type (CCD-based) detector is used because of its wide dynamic range and low-noise. The detectors consist of a thin fluorescent (Gd₂O₂S:Tb or Lu₂SiO₅:Ce) screen, visible light optics and CCD camera. A spatial resolution of 1μm was obtained from its point spread function with high resolution system. Some applications in micro-tomography are shown.

  In order to efficiently perform diffraction and scattering experiments at the SPring-8 facility, three types of position sensitive detectors have been developed. A silicon pixel detector could detect X-rays above 6-keV in single counting mode, and an image accumulated could be read out within 5 msec. A 128-channel microstrip Germanium detector has made it possible for the users to efficiently investigate high resolution Compton scattering experiments. A high energy X-ray imager with a 128 x 128 matrix of YAP crystal has been developed for high energy X-ray diffraction experiments.

  Two types of the silicon avalanche photodiode (Si-APD) array detector have been developed for synchrotron X-ray experiments on nuclear resonant scattering. A 16×2 array of 3×5mm² pixels (thickness: 0.15mm) was designed for large solid angle measurements of the nuclear resonant inelastic scattering on ⁵⁷Fe (nuclear resonant level: 14.4keV). A 4×2 array of 0.5×1 mm² pixels (thickness: 0.05mm) was produced for measurements of the nuclear resonant forward scattering. X-ray detectors using the Si-APD arrays were tested on detection efficiency and timing performance for 14.4-keV X-rays. With a proper readout electronics for each pixel, an array of Si-APDs can be an X-ray detector having a count-rate capacity of up to 10⁸ s^-1 per pixel, position resolution and a sub-nanosecond time resolution.

  Measurements of X-ray polarization provide us with a new probe for the study of the structure of magnetic fields around pulsars and of synchrotron nebulae, the structure of black hole candidates and active galactic nuclei (AGN), and the emission mechanism of γ-ray burst (GRB). The development of polarimeter with higher sensitivity than currently available is necessary for the systematic observation of polarized X-rays from stellar objects. Since directions of K-shell photoelectrons emitted by photoabsorption depend on the electric vector of incident X-rays, the degree of X-ray polarization can be measured by detecting the emission directions of the photoelectrons. For accurate detection of the direction, it is essential to obtain image of a photoelectron track and hence the polarimeter employing the photoabsorption effect simultaneously has the capability of X-ray imaging. For this purpose, we have been developing an optical imaging capability gas proportional counter, which consists of the capillary gas proportional counter (CGPC) and an optical system with an image-intensified CCD camera (I.I.CCD). This paper reviews the recent development of the CGPC.