Introduction to SAXS (Small-angle X-ray scattering), instrumentation, applications

J. Ilavský

Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA
ilavsky@aps.anl.gov

Small-angle scattering of X-rays or neutrons is time tested technique suitable for characterization of microstructural features from few Angstroems to tens of microns and larger. While well known by name and principle, it is, unluckily, often misunderstood or even abused by current generations of scientists. And that at time when, at least from point of view of SAXS beamline scientist, the field of applications broadens up tremendously. Clearly, the education of the principals and methods in current university curriculum on SAXS and SANS is lacking. This is pity as the advancement in X-ray and neutron sources, instrumentation, and detectors - combined with the latest developments in computer modeling - provide tremendous opportunities and capabilities. Current systems can collect broad range of data (up to five decades in sizes), can measure in very short times (nano seconds and shorter), have sensitivities unheard of just few years ago etc. Current experiments can be performed at wide range of wavelengths and with tremendous flux - both on synchrotrons as well as high flux neutron sources. And latest developments in desktop X-ray optics have also resulted in major improvements of desktop SAXS capabilities. The lecture will attempt to summarize the basics of small-angle scattering, current capabilities available on new desktops and at advanced facilities, and present examples of applications from speakers experience. We will discuss methodology, including instrument and radiation selection, absolute intensity calibration, and sample preparation. Software for data reduction and analysis will be briefly listed and summarized. While presentation in the allocated time cannot substitute proper college level course or specialized courses offered routinely by large facilities, it should be a good start for novices and, hopefully, enjoyable and entertaining event for present SAXS/SANS experts.