The use of a variety of synchrotron techniques in the study of cementitious materials

Abstract

The electron synchrotron ’revolution’ is barely twenty years old yet its impact on materials science is immeasurable. Fig.1 captures the essence of synchrotron radiation with the dipole magnet, which is associated with a highly collimated fan of radiation due to the centripetal acceleration of electron bunches responding to the inwardly acting Lorentz force; however dipole magnets often play a secondary role in current “third generation” synchrotrons which also utilize more advanced magnet configurations (wigglers and undulators) that are capable of producing even more brilliant sources of X-radiation. The five main attributes of synchrotron X-ray beams are:• The X-ray beam is intense, such that up to 1012 photons per second might be incident on a sample, thus enabling measurements with excellent counting statistics and/or short collection times.• The radiation is horizontally polarized in the plane of the electron orbit.• The X-ray beam is highly collimated, with a typical working divergence of ∼mrads, such that there is less wastage during its passage through the optical components and a superior angular resolution in the eventual measurement.• The radiation has a smooth continuous 'white' spectrum extending into the hard (penetrating) X-ray region, thus offering the choice of conducting experiments with white radiation or alternatively enabling a free choice of wavelength by use of a monochromator.• Since the electrons move in bunches the synchrotron X-ray source is actually pulsed, at a frequencies in the region of 3×108 s−1.