A novel polymer fibre diffractometer based on a scanning x-ray sensitive charge-coupled device

This paper describes the development of a novel X-ray diffractometer, designed for the study of highly uniaxially oriented polymer fibres. The system is designed around a commercial X-ray-sensitive video camera, which is mounted on a three-circle goniometer. The active element in the X-ray camera is a charge-coupled device (CCD). The data-collection procedure consists of the combination of several diffraction images, obtained with the detector centred at different points in reciprocal space, to construct a composite diffraction pattern representing a linearized section through the symmetry axis of cylindrically averaged reciprocal space. By the combination of several images in this way, it is possible to overcome the traditional problem in fibre photography of information loss, caused by the Ewald-sphere curvature, close to the reciprocal fibre axis. Methods for optimizing the performance of the CCD detector, in terms of both its resolution and sensitivity, are discussed, and the data gathering and processing system is described in some detail. The operation of the system is demonstrated using samples of liquid-crystalline and conventional synthetic polymeric fibres.