sum peak

In EDS analysis, characteristic X-rays emitted from a specimen are detected with a semiconductor detector. Pulse voltages that are proportional to the energies of the detected characteristic X-rays are generated, and then these voltages are measured with a multi-channel pulse-height analyzer. When two different characteristic X-rays almost simultaneously enter the detector, these X-rays cannot be recognized as separate pulses. Thus, an EDS spectrum exhibits a spectral peak at an energy position of the sum of energies of the two characteristic X-rays, together with spectral peaks due to characteristic X-rays of the specimen. The peak is called a "sum peak" and therefore, care must be taken for spectral analysis.

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