Efficiency of Ge Detectors

The efficiency of Ge detectors quoted in the list of specifications by the manufacturer may be a relative full-energy peak efficiency or an absolute 

Consider a case of 10,000 counts being recorded by a 3 in X 3 in Na(Tl) detector under the 1.33-MeV peak of Co. A Ge detector with 10 percent relative efficiency will record only 1000 counts. The FWHM of the Na(Tl) peak is 70 keV the corresponding width of the Ge peak is about 2 keV. Since the total number of counts under the peak is proportional to the product of the FWHM times the peak, the heights of the two peaks are related by 

even though the Ge detector is only 10 percent efficient, relative to the NaI(Tl) crystal, it produces a peak that is 3.5 times higher. 

Another parameter specified by the manufacturer of Ge detectors is the peak-to-Compton ratio (PCR). Looking at Fig. 12.26, the PCR is defined by the equation 

The average of the plateau is taken between 1040 and 1096 keV, in accordance with IEEE Standard No. 325-1971. The PCR is important because it indicates the capability of the detector to identify lov/-energy peaks in the presence of 

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