NEW DEVELOPMENTS IN INSTRUMENTATION FOR X-RAY AND NEUTRON FIBER DIFFRACTION EXPERIMENTS

New instrumentation has been developed for use in X-ray and neutron fi bre diffraction studies to provide automated control of sample positio n, orientation and ambient relative humidity. A sample mount system ha s been constructed for the Keele fibre diffraction camera on beamline 7.2 at the Daresbury Laboratory synchrotron radiation source. This all ows the sample position and orientation to be controlled remotely, wit hout disturbing the sample environment or the detector, and permits th e implementation of efficient data-collection strategies. The system c an be used to record entire datasets without incurring any loss of dat a in the meridional region of the diffraction pattern and has also bee n used to record three-dimensional datasets from fibres exhibiting 'do uble orientation'. The design incorporates a translation feature so th at the effects of radiation damage during data collection can be minim ized. An automated humidity control system has also been constructed a nd can be used in either X-ray or neutron fibre diffraction studies wh ere the water content of samples is a critical parameter and careful c ontrol of the relative humidity of the sample environment is required. This system allows the relative humidity to be controlled according t o a pre-programmed set of instructions and alleviates some of the comm on problems that are encountered with conventional methods that requir e the use of saturated salt solutions. The system is currently install ed on instrument D19 at the Institut Laue-Langevin, Grenoble. Results illustrating the application of these facilities in high-angle fibre d iffraction studies of DNA are presented.