Count rate in EDS measurements

Count rate in EDS measurements
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At high count rates, a pile-up continuum can appear in EDS spectra as a tail on the high energy side of peaks. [1] Figure 1237 employed the same theoretical background modeling program to subtract the EDS backgrounds. However, Figure 1237 (a) shows a good background fit to the spectrum taken at a modest count rate, while the spectrum taken at a high count rate shown in Figure 1237 (b) exhibits strong pile-up effects and thus, the background modeling provides a very poor background subtraction.

Spectra from pure Cobalt standard obtained at 20 kV: (a) at a modest count rate and (b) at a high input count rate

(a)

(b)

Figure 1237. Spectra from pure Cobalt (Co) standard obtained at 20 kV: (a) at a modest count rate and (b) at a high count rate. Adapted from [2]

Table 1237. Pile up continuum and sum peaks.

Characteristic		Peak width (FWHM)	Pile up continuum	Sum peaks
Short	Processing time	Wide peaks		Less
Long	Processing time	Narrow peaks		More
	Count rate		Occurs at high count rates
High	Count rate		Pile up continuum can appear as a tail on the high energy side of peaks	May appear at the end of the tail
X-ray photons			Significant for high energy photons

[1] P. J. Statham, Pile-Up Rejection: Limitations and Corrections for Residual Errors in Energy-dispersive Spectrometers, X-Ray Spectrom. 6 (2), 94-103 (1977).
[2] Peter J. Statham, Limitations to Accuracy in Extracting Characteristic Line Intensities From X-Ray Spectra, J. Res. Natl. Inst. Stand. Technol. 107, 531–546 (2002).

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