Instead of using X-rays of single energy, which is like using light of a single wavelength or colour, energy-dispersive diffraction uses a multi-wavelength "white beam" of X-rays from the synchrotron. The white beam is diffracted by the sample, producing a spectrum with characteristic intensity peaks at specific photon energies. The position of these peaks provides information about the crystal structure of the sample. Shifts in peak position are used to measure internal strains. By scanning the sample through the beam, a 2D or 3D map of strains in the sample can be produced.
The high energy of X-rays from a synchrotron allows the technique to be used on thick samples, such as real engineering components. The high intensity reduces data collection times, so larger samples can be scanned to map internal strains.
The technique is used for strain-scanning of engineering components, for example measuring residual strains in a weld that could cause cracking in service. The high energy and high intensity X-rays can be used to "see" inside chemical processing equipment or high pressure cells. This opens up the possibility of studying chemical reactions and processes in bulk materials under realistic processing conditions.
Diamond Light Source is the UK's national synchrotron science facility, located at the Harwell Science and Innovation Campus in Oxfordshire.
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