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Research Topics

Precision tests of QED
A summary of recent tests of the theory of Quantum Electrodynamics in medium-Z ions. Accelerators, Tokamaks, Electron Beam Ion Traps and other devices are used in these studies.

Theoretical computation of Atomic Form Factors
How can relativistic quantum mechanics predict absorption and scattering coefficients, and are the results accurate? Atomic form factors determine photoelectric cross-sections, elastic and inelastic scattering cross-sections and X-ray (Bragg-Laue) coherent diffraction profiles. Our Web database has been receiving 10000-20000 hits per month since itís electronic installation as one of the three major references for atomic form factors and attenuation coefficients. Reliable knowledge of these factors is required for conventional fields such as crystallography and radiography, and also for the new fields of X-ray Anomalous Fine Structure (XAFS) and Multiple-wavelength Anomalous Dispersion (MAD).

Experimental measurement of the atomic form factors, attenuation and scattering in matter
Looks at the importance of careful attenuation measurement in differentiating between different theories. Our recent experiments are two orders of magnitude more accurate than earlier work and reveal new physics, new processes and new applications. Major questions remain.

Novel High-energy Sources for QED tests
A problem in most X-ray QED measurements is the presence of satellite contamination and Doppler shifts and broadening from fast beam sources. Recently, sources known as Electron Beam Ion Traps (pictured) have been shown to avoid much of these problems, and still allow desired charge states to be produced and measured.

Synchrotron Beamline Developments and XAFS
Diagnostics used to measure flux and energy in synchrotrons are in a state of development.

XAFS and Solid State Physics: Theory and Experiment
Some third or more of Australian synchrotron research uses XAFS (and the related technique called XANES) to identify band distances, chemical valence, nearest neighbour coordination and geometry, and local structure.

Our group is directly involved with several developments and proposed beam-lines at the Australian Synchrotron.

Powder Diffraction and X-ray Crystallography
Powder Diffraction is often required for structural determination of biologically active molecules, viruses, proteins or enzymes as well as for small inorganic molecules, especially where the samples cannot be grown into large crystals.

These issues impact upon X-ray diffraction theory and the interaction of X-rays with photographic emulsions. Applications of these ideas have led to new calibration devices for radiography and mammography, now patented in the US as part of the Quantum Metrology Group effort in the Atomic Physics Division at the National Institute for Standards and Technology, USA.



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