,
2
Detector response defined in terms of an effective
detector area, A, given by
where
Np = net photopeak count rate
The detector response, in general, varies as a function of
the gamma ray angle of incidence and is normally written as
A=
AOR
(G)
(5)
where
A. = detector photopeak count rate for unit flux incident
perpendicular to detector face
(*)
R’{6) = ratio of detector response at angle
G
to that at B= 0°
Determine A. and R (6) experimentally for a given detector.
Combining Eq’s 4 and 5 with Eq. 3 leads to an expression
relating measured photopeak count rate to source activity
in the soil.