GammaVision
®
v7 (A66-BW) 783620H / 1013
The correction is not applied to unknown peaks. The peak values in the isotope/peak list in the output report are uncorrected values. The peak uncertainty is maintained as a constant percentage. The factor is linearly interpolated between the points in the table and linearly extrapolated outside the energy range of the table points.
The geometry correction table is stored in the spectrum file (
.SPC
). The correction can be enabled or disabled for a specific analysis.
6.10.5.1. Example
As an example of this correction, two spectra were taken of the same point source (Fig. 249). In case 1, the source was about 4 cm from the end cap and on-axis of the detector. The second geometry (case 2) is with the source about 7.5 cm from the center of the detector in a position in the plane of the end cap of the detector.
Table 8 shows the analysis of the two spectra for the peaks due to
154
Eu. The ratio of the peak count rates is shown in column 4. These values are entered into the geometry table. The spectrum was re-analyzed with the geometry correction turned on. The comparison of all three analyses is shown in Table 9.
Note that the
155
Eu activity is not corrected as much as needed. This is primarily due to all of the
155
Eu gammaray lines falling below the lowest energy in the correction table. It is in these low energies that the differences in the geometries is most noticeable.
Fig. 249. Example Geometries
Used.
The geometry correction table can be made automatically using analysis results files (
.UFO
) of the pairs of geometries or manually by entering the correction factor and energy pairs.
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