Extending the depth range in energy-dispersive X-ray stress analysis by simultaneous multi-detector data acquisition in equatorial scattering geometry

A scattering geometry for depth-resolved energy-dispersive X-ray stress analysis on polycrystalline materials is introduced. Via simultaneous data acquisition during a sin² ψ measurement using two detectors arranged in the horizontal diffraction plane, it aims to extend the accessible information depth to the free surface as well as deeper material zones. While data acquisition with the first detector takes place in a symmetrical configuration with regard to the incident and exit angles, α_i and α_e, respectively, the second detector runs in an asymmetrical mode, defined by α_i < α_e. Therefore, the scattering vectors assigned to the two diffraction geometries run in different tilt planes during a χ scan of the sample performed in the Eulerian cradle. Treatment of the data recorded in the asymmetric diffraction mode requires modifications of the fundamental equation of X-ray stress analysis, which are discussed using the example of measurements performed on a unidirectionally ground ferritic steel sample.