What is meant when an HPGe detector is said to be 30 efficie

What is meant when an HPGe detector is said to be 30% efficient?

Solution

A relative 30% HPGe detector has 30% of efficiency expected from 3 in x 3 in NaI detector at 1.33MeV. Although useful as an approximation of detector performance, due to difference in detector geomateries and mounting apparatuses, such sweeping generalization can be erroneous for accurate measurement. It is best to characterize the detector efficiency and resolution, a method described by ANSI/IEEE 325-1996.