X-ray instruments
The small-angle x-ray scattering (SAXS) instrument in the Bragg Institute has suffered a major breakdown; as a consequence the instrument will be out of working order until at least February 2008.
The x-ray reflectometer has recently been commissioned to examine reflectivity from free-liquid surfaces. This will allow the instrument to perform exciting work in many more areas, such as protein/lipid/surfactant adsorption at interfaces.
Problems with evaporation, vibration and acoustic noise have been solved with a specially designed sample can, see photo below. The sand is necessary to damp low-frequency vibrations passed up through the instrument.
The sample and instrument are stable enough to measure both specular and off-specular scattering, from the air-liquid interface in a quick and easy manner. The diagrams below show the reflectivity (and fits) from pure water, and from a sodium dodecyl sulphate (SDS) solution.
As expected the pure water has a roughness of 2.8 ? - its literature value. SDS adsorbs at the air-water interface and forms a layer that is ~21 ? thick. Each of the specular curves was measured in around 2 minutes, with the off-specular scattering taking about an hour.
Future advances in this sample environment will include temperature control and variable gas/humidity atmospheres. We aim to access temperature ranges between 0 and 150°.