New Developments in Instrumentation for X-ray and Neutron Fibre Diffraction Experiments

Abstract

New instrumentation has been developed for use in X-ray and neutron fibre diffraction studies to provide automated control of sample position, orientation and ambient relative humidity. A sample mount system has been constructed for the Keele fibre diffraction camera on beamline 7.2 at the Daresbury Laboratory synchrotron radiation source. This allows the sample position and orientation to be controlled remotely, without disturbing the sample environment or the detector, and permits the implementation of efficient data-collection strategies. The system can be used to record entire datasets without incurring any loss of data in the meridional region of the diffraction pattern and has also been used to record three-dimensional datasets from fibres exhibiting `double orientation'. The design incorporates a translation feature so that the effects of radiation damage during data collection can be minimized. An automated humidity control system has also been constructed and can be used in either X-ray or neutron fibre diffraction studies where the water content of samples is a critical parameter and careful control of the relative humidity of the sample environment is required. This system allows the relative humidity to be controlled according to a pre-programmed set of instructions and alleviates some of the common problems that are encountered with conventional methods that require the use of saturated salt solutions. The system is currently installed on instrument D19 at the Institut Laue–Langevin, Grenoble. Results illustrating the application of these facilities in high-angle fibre diffraction studies of DNA are presented.