Vii. X-ray Diffuse Scattering Academic and Research Staff Joint Services Electronics Program (contract Daag29-78-c-0020)

This research program centers around a two-spectrometer x-ray diffuse-scattering system based on a Rigaku 12-kW rotating-anode x-ray generator. The apparatus is designed in such a way that one may easily tailor the instrumental resolution function to optimize studies of structure and fluctuations in a vast range of physical systems. Angular resolution of 1.8 seconds of arc and sample temperature control of 2 mK between 10 K and 500 K are available. We are currently implementing a position-sensitive detection system to allow rapid scans over a wide range of scattering angles, again with continuously variable resolution. Our current research program emphasizes structure and melting transitions both for monolayer physiadsorbed films on graphite and for layered liquid crystals. The surface experiments involve in situ high-precision vapor-pressure and surface-coverage measurements. Experiments are also performed using the x-ray synchrotron facilities at D.E.S.Y. (Hamburg, Germany) and S.L.A.C. (Stanford). We are currently designing a two-spectrometer high-resolution x-ray system to be permanently located at the National Synchrotron Light Source under construction at Brookhaven National Laboratory.