Fig. 6
Observed acquisition photopeak (a, 187–229 k) and wide-spectrum (b, 18–680 keV) count rates vs. XW . The term XW is the product of activity and observed acquisition count rate in a given window (photopeak or wide spectrum, respectively), divided by the observed primary photon count rate. Solid lines represent the non-linear curve fit forced through origin of Eq. 3 to the data in the usable system range, allowing to resolve the camera calibration factor and the dead-time constant as per Method B (full-range CF). Data is shown for each detector separately, and averaged. Dotted lines represent the average calibration factor for both detectors (a, 9.40 cps/MBq; b, 9.36 cps/MBq)