Back-Reflection Energy-Dispersive XRD for Unprepared Samples
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Solution Overview
Problem
Conventional X-ray diffraction techniques are sensitive to sample morphology, making it difficult to analyze unprepared samples, such as whole rocks or precious archaeological artifacts, without damaging them.
Innovation Solution
The method employs back-reflection energy-dispersive X-ray diffraction with a fixed diffraction angle of approximately 180°, which reduces sensitivity to sample distance and morphology. This approach allows for the use of non-prepared samples and suppresses fluorescence signals by recording and processing multiple spectra at different energy settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional XRD techniques are used, then diffraction analysis can be performed, but the analysis is sensitive to sample morphology and requires prepared samples
Solution Approach 1:
The patent changes the diffraction angle parameter to substantially 180° (back-reflection geometry) and uses energy-dispersive detection with multiple photon energy settings. This parameter change makes the diffraction spectrum insensitive to sample distance and morphology, allowing analysis of unprepared samples while maintaining measurement reliability
Solution Approach 2:
The patent transitions from angle-dispersive to energy-dispersive detection, adding the energy dimension to the measurement. By detecting photons at multiple energy levels and processing spectra from different energy settings, the method overcomes fluorescence interference and achieves reliable analysis of unprepared samples
2Quantity of substance
If broadband X-ray source is used, then diffraction information can be obtained, but fluorescence signals obscure diffraction signals
Solution Approach 1:
The patent uses periodic action by recording spectra at multiple discrete photon energy settings (e.g., 8 kV, 4 kV, 2 kV). Each energy setting provides a spectrum where certain fluorescence signals are suppressed, and by combining these periodic measurements, complete diffraction information is obtained with fluorescence interference removed
Solution Approach 2:
The patent converts the harmful fluorescence effect into a beneficial selection criterion. By choosing specific photon energy settings that are just below absorption edges of elements in the sample, the method ensures that fluorescence signals from those elements are not excited, while still obtaining diffraction information. The fluorescence problem becomes a guide for selecting optimal energy settings
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The technique enables the analysis of unprepared samples with improved signal strength and reduced fluorescence interference, allowing for the determination of crystal spacings over a wider range than conventional methods, and facilitating the analysis of samples that were previously difficult to prepare.
Implementation Method 1
an X-ray beam with, ideally, a single wavelength λ is diffracted by a sample through a range of distinct scattering angles 2θ, according to the Bragg equation
Implementation Method 2
one fixes the scattering angle and scans the X-ray wavelength (equivalently, the X-ray energy)... together with an energy-resolving detector
Implementation Method 3
The use of this extreme angle, effectively back-reflection toward the source, helps to make the diffraction spectrum largely insensitive to sample distance or morphology
Implementation Method 4
Said plurality of spectra may be processed together to obtain diffraction information that is substantially independent of fluorescence phenomena over a greater set of energies
Data Source
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AI summary
Methods and apparatus are provided for performing back-reflection energy- dispersive X-ray diffraction (XRD). This exhibits extremely low sensitivity to the morphology of the sample under investigation. As a consequence of this insensitivity, unprepared samples can be analysed using this method. For example, in a geological context, whole rock samples become amenable to analysis. A composite diffraction spectrum can be produced using information from different recorded spectra in different energy sub-ranges. The composite spectrum excludes fluorescence signals that would otherwise obscure the diffraction signals.