Figure 17 shows the pulse height spectra for the four pileup tests. The Al-K line is the largest peak at about 300 ADU and the remaining features are pileup peaks centered at nE ADU. As the degree of pileup increases, the amplitude of the primary peak decreases while the pileup peaks increase in amplitude. The degree of pileup estimated for these and other tests discussed on our web page was found by fitting Gaussians to, and finding the area under, each peak. While the degree of pileup can be determined easily in monochromatic data, it would be difficult for astrophysical objects with realistic spectra.
