Evaluation of peak-to-total ratio for germanium detectors

An equation for the peak-to-total ratio, P, of a germanium detector is proposed in the following form. P=var epsilonp/var epsilont+a(V/A)+b(V/A)2/2 where var epsilonp/var epsilont is the ratio of the photoelectric to the total detection efficiency for a germanium detector, V/A is the volume-to-surface ratio of the detector, and the parameters of a and b are experimentally given as a function of incident photon energy. The first term in the right side of the equation expresses the fractional single photoelectric-to-total interaction between photons and the detector. The second and third terms correspond to the multiple interactions. The peak-to-total ratios for the germanium detector with a sensitive volume up to 200 cm3 were calculated by the equation. They coincide with the experimental values to within an uncertainty of several percent in the energy region 0.3–3 MeV.