X-ray absorption spectrum detector is an advanced analytical device that places a sample between a high-brightness X-ray light source and an energy-resolved spectral detector, and obtains its absorption spectral characteristics by measuring the absorption intensity of X-rays in different energy segments of the sample. When the incident multi-energy X-ray penetrates the sample, different elements and their chemical bond states have different absorption cross-sections for photons in a specific energy range, and thousands of fine and accurate spectral lines will appear in the signal exiting the detector, and their energy positions and absorption depths together form a clear fingerprint. By accurately fitting and contrasting these spectral lines, it is possible not only to classify and identify individual substances with high sensitivity – such as different types of plastics, metal oxides, organic compounds, ore samples, and even illicit drugs and flammable and explosive substances – but also to quantitatively measure thickness and concentration based on the transition characteristics of the absorption edges. Experimental results show that when the composition of the measured object is pure, the system can distinguish the element type and valence state at the millielectron volt level. When the sample is a multi-component system, multivariate analysis and machine learning methods can also be combined to realize the inversion of component proportions and spatial distribution imaging. Thanks to the detector's high energy resolution and fast readout ability, the instrument is gradually expanding to application scenarios such as online monitoring, process control and on-site rapid screening, providing a non-destructive, accurate and quantitative analysis method for materials science research, environmental monitoring and safety protection.

The following figure shows a comparison of the X-ray absorption spectra of 15 plastics, and it can be seen that the spectral characteristics of the 15 to 25 keV range are very different.