783620H / 1013 6. ANALYSIS METHODS
For the above example, if the PBC match width is 0.1 keV, then PBC subtraction will not be applied to either peak. If the PBC match width is 0.5 keV, then PBC subtraction will be applied to the 186.20 keV peak only, but not to the 185.70 keV peak, even if the latter is within the PBC
match width. In the table below, some scenarios are tabulated.
PBC Peak E = 186.00 keV
Peak No.
Peak E (keV)
Peak #1
Peak #2
185.70
186.20
PBC Total Match Width (f * FWHM) in keV
0.1
0.2
0.5
PBC — No
PBC — No
PBC — No
PBC — Yes
PBC — No
PBC — Yes
If there are multiple PBC peaks associated with a spectral peak, and if all those PBC peaks are within the PBC Match Width, then that peak is subject to multiple PBC corrections. For example, if there is another PBC peak at 186.3 keV, that PBC peak would be associated with the
186.20 keV peak, leading to two PBC peaks to subtract from. In addition, if there is another PBC peak at 185.6 keV, then that PBC peak would be associated with the 185.7 keV only. When multiple PBC are applied, the uncertainties of each PBC are propagated accordingly. See the discussion in Section 6.12.12.
Note that with the above “association rule” for matching PBC with the closest peak, the PBC match width can be set larger than the default value of 0.2 * FWHM and should not lead to PBC peaks being incorrectly applied to spectral peaks.
6.10.5. Geometry Correction
The geometry correction is used to adjust the activities reported in a sample of a given source/ detector geometry when the system was calibrated using a different source/detector geometry.
This is useful when many different geometries are used in a laboratory and calibrated sources are not available for all the geometries used. For more information, see Section 5.5.1.4.
The correction factor multiplies the peak activity for each peak in the library as shown in Eq. 87.
The factors are stored as a function of energy.
(87)
where:
A
Geo
A
= corrected activity for a given energy
= uncorrected activity for a given energy
GeoFac = the correction factor for that energy
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