The use of a Hamamatsu X-ray image intensifier with a cooled CCD as a solution X-ray scattering detector

Abstract

CCD detectors are now widely used in many synchrotron small-angle X-ray scattering beamlines. The use of an X-ray image intensifier with cooled CCD (XR-II + CCD) was studied, especially for use in synchrotron solution X-ray scattering. Two samples, polystyrene latex and apoferritin, were used. These two samples have fine structure in the solution scattering profile due to symmetry and narrow size distribution. The recorded scattering profile, in comparison with that obtained by a position-sensitive proportional counter (PSPC), showed that XR-II + CCD has a much smaller practical dynamic range (100:1) than that of a pixel well (7500:1). This limited dynamic range was overcome by placing various-size masks on the detection plane, thereby eliminating the high-intensity region. The images recorded with various masks were combined, and the reconstituted solution scattering profile was submitted to various analyses, including Guinier analysis, power-law analysis, size distribution analysis and calculation of radial density distributions. The results were the same as those obtained with the PSPC. This indicates that spatial distortion as well as shading, a decrease in sensitivity from the centre to the edge of the detecting region [Amemiya, Ito, Yagi, Asano, Wakabayashi, Ueki & Endo (1995). Rev. Sci. Instrum. 66, 2290-2294], have very little effect on the SAXS results. This paper presents a practical protocol for obtaining a reliable solution scattering profile given the limitations of XR-II + CCD for synchrotron solution X-ray scattering.