5.3 Analytical sensitivity

Intrinsic efficiency of radiation detectors is proportional to the detector sensitive volume. Therefore, radiation detectors designed for laboratory analysis can have a comparatively larger intrinsic efficiency than that of the portable instruments, for which the requirements of low weight and power consumption are a compulsory requirement.

However, the geometry efficiency in laboratory analysis is limited to the physical size of the sample, whereas in field measurements the effective sample size depends on the energy of the radiation and its attenuation in the media. This can be illustrated by the estimation of such volumes for gamma spectrometry analysis: in laboratory analysis the samples is limited to about one cubic decimeter, whereas for in-situ measurements it can reach several cubic meters. The latter leads to a significant difference in the time required for attaining similar counting statistics.