Measuring the linearity of X-ray detectors: consequences for absolute attenuation, scattering and absolute Bragg intensities

Barnea, Z.; Chantler, Christopher T.; Glover, Jack L.; Grigg, Mark W.; Islam, Mohammad Tauhidul; Jonge, Martin D. de; Rae, Nicholas A.; Tran, Chanh Q.

doi:10.1107/s0021889811004493

Cited by 10 publications

(8 citation statements)

References 46 publications

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“…Higher-order undulator harmonics have the potential to deposit substantial charge in the sensor and can therefore severely affect detector counting capabilities (Barnea et al, 2011). A multiple-foil method has been previously applied to quantify the harmonic fraction at <0.01% (Tran et al, 2003), which is further reduced by the use of a Si(111) double-crystal monochromator (DCM).…”

Section: Measurementmentioning

confidence: 99%

Success and failure of dead-time models as applied to hybrid pixel detectors in high-flux applications

Sobott¹,

Broennimann²,

Schmitt³

et al. 2013

J Synchrotron Radiat

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The performance of a single-photon-counting hybrid pixel detector has been investigated at the Australian Synchrotron. Results are compared with the body of accepted analytical models previously validated with other detectors. Detector functionals are valuable for empirical calibration. It is shown that the matching of the detector dead-time with the temporal synchrotron source structure leads to substantial improvements in count rate and linearity of response. Standard implementations are linear up to $ 0.36 MHz pixel À1; the optimized linearity in this configuration has an extended range up to $ 0.71 MHz pixel À1; these are further correctable with a transfer function to $ 1.77 MHz pixel À1 . This new approach has wide application both in highaccuracy fundamental experiments and in standard crystallographic X-ray fluorescence and other X-ray measurements. The explicit use of data variance (rather than N 1/2 noise) and direct measures of goodness-of-fit ( r 2 ) are introduced, raising issues not encountered in previous literature for any detector, and suggesting that these inadequacies of models may apply to most detector types. Specifically, parametrization of models with non-physical values can lead to remarkable agreement for a range of count-rate, pulse-frequency and temporal structure. However, especially when the dead-time is near resonant with the temporal structure, limitations of these classical models become apparent. Further, a lack of agreement at extreme count rates was evident.

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Section: Measurementmentioning

confidence: 99%

Success and failure of dead-time models as applied to hybrid pixel detectors in high-flux applications

Sobott¹,

Broennimann²,

Schmitt³

et al. 2013

J Synchrotron Radiat

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“…Since at higher energies harmonics are generally negligible (Barnea et al, 2011), the plots measure the linearity of the detector and counting chain. Since at higher energies harmonics are generally negligible (Barnea et al, 2011), the plots measure the linearity of the detector and counting chain.…”

Section: X-ray Mass Attenuation Of Goldmentioning

confidence: 99%

“…Many investigations use detectors (charge-coupled devices, pixel-based or imaging detectors) which may only be linear to a few percent or which may only be linear over a single decade (Barnea et al, 2011). The type of investigation outlined here, which will allow determination of beamline-specific effects dependent on the geometry of the experiment and thereby permit determination of beamline-independent results for attenuation or XAS, is invaluable in assigning a confidence level to final results.…”

Section: X-ray Mass Attenuation Of Goldmentioning

confidence: 99%

New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique

et al. 2012

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An extension of the X-ray extended-range technique is described for measuring X-ray mass attenuation coefficients by introducing absolute measurement of a number of foils - the multiple independent foil technique. Illustrating the technique with the results of measurements for gold in the 38-50 keV energy range, it is shown that its use enables selection of the most uniform and well defined of available foils, leading to more accurate measurements; it allows one to test the consistency of independently measured absolute values of the mass attenuation coefficient with those obtained by the thickness transfer method; and it tests the linearity of the response of the counter and counting chain throughout the range of X-ray intensities encountered in a given experiment. In light of the results for gold, the strategy to be ideally employed in measuring absolute X-ray mass attenuation coefficients, X-ray absorption fine structure and related quantities is discussed.

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“…In these cases, despite a large harmonic on different beamlines which would quite invalidate absorption or XAFS accuracies and interpretation, the quantification of these components allows an accurate determination of the correct = ½ , irrespective of monochromator detuning and especially in an energy range from 10-11 keV down to 5 keV. Such tests also directly investigate the linearity of detectors, relating to such issues as detector saturation or intrinsic non-linearities (Barnea et al, 2011).…”

Section: Systematics Affecting Observed Precision: Harmonic Componentsmentioning

confidence: 99%

“…Two key topics are raised in detail by Nomura (2012) and Srihari et al (2012), namely the calibration of energy and the characterization of detector non-linearities. We will attempt not to duplicate that material here, but both issues are obviously critically important in determining and improving the quality of XAFS (Barnea et al, 2011). Common systematic errors in the energy determination of an XAFS or XANES measurement, in part beautifully discussed by Diaz-Moreno (2012), include the drifts and offsets of calibration and monochromation.…”

Section: Limitations To Precisionmentioning

confidence: 99%

A step toward standardization: development of accurate measurements of X-ray absorption and fluorescence

Chantler

Barnea

Tran

et al. 2012

J Synchrotron Radiat

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This paper explains how to take the counting precision available for XAFS (X-ray absorption fine structure) and attenuation measurements, of perhaps one part in 10(6) in special cases, to produce a local variance below 0.01% and an accuracy of attenuation of the order 0.01%, with an XAFS accuracy at a similar level leading to the determination of dynamical bond lengths to an accuracy similar to that obtained by standard and experienced crystallographic measurements. This includes the necessary corrections for the detector response to be linear, including a correction for dark current and air-path energy dependencies; a proper interpretation of the range of sample thicknesses for absorption experiments; developments of methods to measure and correct for harmonic contamination, especially at lower energies without mirrors; the significance of correcting for the actual bandwidth of the beam on target after monochromation, especially for the portability of results and edge structure from one beamline to another; definitions of precision, accuracy and XAFS accuracy suitable for theoretical model analysis; the role of additional and alternative high-accuracy procedures; and discusses some principles regarding data formats for XAFS and for the deposition of data sets with manuscripts or to a database. Increasingly, the insight of X-ray absorption and the standard of accuracy needed requires data with high intrinsic precision and therefore with allowance for a range of small but significant systematic effects. This is always crucial for absolute measurements of absorption, and is of equal importance but traditionally difficult for (usually relative) measurements of fluorescence XAFS or even absorption XAFS. Robust error analysis is crucial so that the significance of conclusions can be tested within the uncertainties of the measurements. Errors should not just include precision uncertainty but should attempt to include estimation of the most significant systematic error contributions to the results. This is essential if the results are to be subject to deposition in a central accessible reference database; it is also crucial for specifying a standard data format for portability and ease of use by depositors and users. In particular this will allow development of theoretical formulations to better serve the world-wide XAFS community, and a higher and more easily comparable standard of manuscripts.

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Measuring the linearity of X-ray detectors: consequences for absolute attenuation, scattering and absolute Bragg intensities

Cited by 10 publications

References 46 publications

Success and failure of dead-time models as applied to hybrid pixel detectors in high-flux applications

Success and failure of dead-time models as applied to hybrid pixel detectors in high-flux applications

New consistency tests for high-accuracy measurements of X-ray mass attenuation coefficients by the X-ray extended-range technique

A step toward standardization: development of accurate measurements of X-ray absorption and fluorescence

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