Polychromatic Small-Angle X-Ray Scattering (SAXS)
Small-angle scattering with broadband illumination and energy-resolved detection.
Also known as: energy-dispersive SAXS (ED-SAXS, EDSAXS), spectral SAXS (sSAXS, SSAXS), pink-beam SAXS.
Small-angle X-ray scattering (SAXS) normally uses monochromatic X-rays so detector position maps cleanly to a single scattering vector. With a broader spectrum, the same detector position can correspond to different scattering vectors, which can blur features in the scattering curve.
Polychromatic SAXS, addresses this by combining broadband illumination with a detector that measures both position and photon energy. The pnCCD based Colour X-Ray Camera (CXC) provides this energy and position information for each detected photon, enabling energy-resolved SAXS workflows.
Why use a polychromatic beam
A broader spectrum can increase usable photon flux compared to strictly monochromatic operation. This can reduce exposure time in flux-limited SAXS measurements, including time-resolved experiments. Pink-beam SAXS work demonstrates the feasibility of SAXS with finite bandwidth and reports shorter exposures due to higher beam intensity.
Key points
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Uses more of the available source spectrum
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Can reduce exposure time in suitable geometries
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Supports measurements where speed matters
Comparison of traditional SAXS (upper image) and advanced polychromatic SAXS (lower image). The spatial and energy resolving capabilities of the CXC allow a deeper understanding of the sample.
How the CXC makes polychromatic SAXS practical
With a broadband spectrum, you must account for photon energy when converting detector position to scattering vector. The CXC records both the arrival position and the energy of detected photons, so analysis can calculate scattering in an energy-resolved way and then combine results into a consistent scattering curve.
This approach is widely described as spectral SAXS or energy-dispersive SAXS. In energy-dispersive SAXS, a polychromatic source is used and an energy-sensitive detector records scattered X-ray energy.
Key points
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Energy and position are captured in the same dataset
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q can be reconstructed with reduced bandwidth-induced blur
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One detector supports broadband operation without energy scanning
The CXC records the position and energy of each detected X-ray photon, enabling energy-resolved projection data.
What this enables for SAXS users
Polychromatic SAXS is mainly attractive when the measurement is limited by flux or time. By avoiding strict monochromatisation, the setup can prioritise photon throughput while retaining the ability to interpret the data using energy resolution.
Key points
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Faster acquisition for suitable samples and beam conditions
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Stable geometry without changing beam energy during a measurement series
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Time-resolved SAXS workflows that benefit from higher flux
Learn more
If you are interested in polychromatic SAXS, or want to discuss whether a spectral SAXS approach is realistic for your flux, sample, and geometry, please contact us to discuss your application.
If you are specifically looking for commercially available systems built on this core technology, explore our range of Colour X-Ray Camera (CXC) products here.