A method to determine the absolute harmonic content of an X‐ray beam using attenuation measurements

Glover, Jack L.; Chantler, Christopher T.

doi:10.1002/xrs.1206

Cited by 12 publications

(5 citation statements)

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“…This is crucial in demonstrating the reproducibility of results and permitting absolute tests of theory. This includes but is not limited to: energy calibration [23,24] and correction of lattice parameters [25,26], scattering and fluorescent radiation [27,28], detector non-linearity [29] and harmonic contamination [30,31], nanoroughness [32] and finite spectral-bandwidth [33]. We show that harmonic contamination and fluorescent radiation in this work were not significant factors, whilst the bandwidth of the beam had a large impact upon foils of different thickness near the absorption edge.…”

Section: Sources Of Systematic Errormentioning

confidence: 70%

Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV–28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum

Tantau

Chantler

Bourke

et al. 2015

J. Phys.: Condens. Matter

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We use the x-ray extended range technique (XERT) to experimentally determine the mass attenuation coefficient of silver in the x-ray energy range 11 kev-28 kev including the silver K absorption edge. The results are accurate to better than 0.1%, permitting critical tests of atomic and solid state theory. This is one of the most accurate demonstrations of cross-platform accuracy in synchrotron studies thus far. We derive the mass absorption coefficients and the imaginary component of the form factor over this range. We apply conventional XAFS analytic techniques, extended to include error propagation and uncertainty, yielding bond lengths accurate to approximately 0.24% and thermal Debye-Waller parameters accurate to 30%. We then introduce the FDMX technique for accurate analysis of such data across the full XAFS spectrum, built on full-potential theory, yielding a bond length accuracy of order 0.1% and the demonstration that a single Debye parameter is inadequate and inconsistent across the XAFS range. Two effective Debye-Waller parameters are determined: a high-energy value based on the highly-correlated motion of bonded atoms (σ(DW) = 0.1413(21) Å), and an uncorrelated bulk value (σ(DW) = 0.1766(9) Å) in good agreement with that derived from (room-temperature) crystallography.

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Section: Sources Of Systematic Errormentioning

confidence: 70%

Structure determination from XAFS using high-accuracy measurements of x-ray mass attenuation coefficients of silver, 11 keV–28 keV, and development of an all-energies approach to local dynamical analysis of bond length, revealing variation of effective thermal contributions across the XAFS spectrum

Tantau

Chantler

Bourke

et al. 2015

J. Phys.: Condens. Matter

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“…The measured harmonic content did not differ significantly from zero for any of these measurements. The effective harmonic parameter α (defined in [41]) remained below 10 −5 for all our measurements. This demonstrated the linearity of our detection system far beyond the range of our main measurements.…”

Section: Harmonicsmentioning

confidence: 81%

Measurement of the x-ray mass-attenuation coefficients of gold, derived quantities between 14 keV and 21 keV and determination of the bond lengths of gold

Glover

Chantler

Barnea

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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Can we test QED? Is it true? We are the only group to test QED in Australia and have just had a breakthrough reported in Physics Today. This was an international team effort and doctoral thesis work but also with contributions from an Honours/Masters student. 2. How can we get structural information from an isolated quantum system-molecule, gas or non-crystalline solid? We have been the world leaders in extracting structural and quantum information from atomic, molecular and organometallic (i.e. biophysical) systems with advanced experiments and analysis, advancing the techniques used by more than 30% of all synchrotron researchers across the world. 3. Can I develop or invent a new field of physics? Yes but probably not in Masters! Recent doctoral students have developed new fields of non-destructive nanoroughness measurement; and electron inelastic scattering (mean free path) experiment and theory; or made major developments in dominant fields of X-ray science or relativistic Quantum Mechanics. • Facilities: X-ray labs; Synchrotrons around the world & Melbourne; EBIT labs around the world. Our local laboratories develop new technology in-house, & ask fundamental questions about the universe & matter. • Two honours students (2005) produced 3 major papers from honours (one high profile Phys. Lett.). Three honours students (2006) got the best experimental thesis in the School (Ramm Prize), and one of the top 3 theory theses. Both students in 2008 got top marks in theory and experiment. These great results reflect on them, the potential of the field & our group. Martin de Jonge was awarded the Chancellor's Prize (best Doctoral Thesis at Melbourne University), 'Best Synchrotron Thesis in Australia', flew off to an exciting career at the Advanced Photon Source (Chicago) & has now returned to get first light on the Australian Synchrotron on a key beamline. We receive national & international awards for group achievements. Our experiments are two orders of magnitude more accurate than all earlier publications in the field. 1 This has opened up exciting new opportunities & opened our eyes to new phenomena and new ways of testing earlier assumptions. Our experiments have been the first to measure scattering 2 & synchrotron bandwidth in photoabsorption experiments, have redefined the international standards for (powder) diffraction 3 , and have placed the field of X-ray Absorption Fine Structure (XAFS) on an absolute footing for the first time. Our relativistic atomic theory and tabulation 4 is the most successful currently available in terms of agreement with experiment. Theory must be based on condensed matter physics near absorption edges to explain detailed oscillations, which in turn raises new questions. Honours students have developed new theory & computational tools for condensed matter science, including the first extended XAFS solution avoiding 'muffin-tin' approximations 5 & the largest (organometallic) XAFS modelled without this assumption, 6 with major implications for biological

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“…The fitted effective harmonic percentage represents the product of the overall detector efficiency and optic losses compared with that of the fundamental (8.04 keV) energy, multiplied by the actual harmonic percentage. This has been discussed elsewhere; note that the air absorption is negligible so that the differential efficiency is dominated by the source, detector, and window components. The amplitude of the spectral intensity will vary from first‐order to second‐order.…”

Section: Experiments and Key Characteristicsmentioning

confidence: 99%

Count‐rate, linearity, and performance of new backgammon detector technology

et al. 2019

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The meander wire backgammon technology has high levels of flux and spatial linearity across a wide range of energies. One of the attractive features of these technologies is the stability of response and robustness under long X-ray exposure, compactness, and portability. A key problem historically has been the limited range of count-rate for processing to the optimum resolution. We report dramatic advances in this and other areas appropriate for high-accuracy experiments including tests of quantum electrodynamics, fundamental relativistic atomic physics, X-ray calibration, and crystallography. We illustrate this technology applied to the K 1,2 spectra of titanium, chromium, and copper. The quality of the spectra permits deeper insight into atomic and solid state science and permits accurate measurement of energy and relativistic atomic physics processes, below 1-m accuracy or down to 1 ppm in energy. 218 The University of Melbourne (UM) backgammon detector relies on a sophisticated data acquisition system specifically developed for the detector and its use as part of our Johann-type curved crystal X-ray spectrometer. The design allows single photon counting over a wide range of count rates. [30]

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A method to determine the absolute harmonic content of an X‐ray beam using attenuation measurements

Cited by 12 publications

References 12 publications

Measurement of the x-ray mass-attenuation coefficients of gold, derived quantities between 14 keV and 21 keV and determination of the bond lengths of gold

Count‐rate, linearity, and performance of new backgammon detector technology

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