Branching Ratio Variation with Flux

Branching ratios can be defined as the number of x-rays detected in one grade selection divided by the total number of x-rays detected. The branching ratio is not only energy dependent but is flux dependent. The laboratory pileup data can be used to compute the effect of flux on the branching ratios. These ``branching ratio epsilons'' are presented in Figs.  4.30 and  4.31, which show some variation between the various CCDs. These numbers are relative correction factors to the branching ratio per detected g02346 x-ray per quadrant. For example, if the BR epsilon equals $4\times10^{-5}$, and there are 1000 x-rays per quadrant per frame, then the relative correction to the branching ratio is 4%. The numbers in Figs.  4.30 and  4.31 are specfically the number of G02346 events in the $K_{\alpha}$peak divided by all events in the peak. The effect of pileup on branching ratio has a direct effect on methods which use the branching ratio to determine the depletion depth. An example of this method is discussed in section  4.6.2.

  

Figure 4.30: Branching ratio epsilons from data set for elements Al - V

  

Figure 4.31: Branching ratio epsilons from data set for elements Fe - Ge