783620H / 1013 6. ANALYSIS METHODS
The variance due to the change in the peak background is taken to be the increase in the peak background, N
p
. Therefore, after PBC, the total absolute uncertainty (in counts) for the net peak area is calculated as:
(134)
Note that for PBC, only the absolute uncertainties (not relative) are added in quadrature. After the PBC correction, the relative uncertainty in percent is calculated as:
(135)
If the PBC corrected area is exactly zero, the relative uncertainty is set at 1000% (or 10.0), the default value used in all cases where the activity is zero.
Note that when PBC is enabled, the counting uncertainty for a peak always has PBC contributions. That is, the counting uncertainty calculated before PBC (
σ
0
in Eq. 131) is not saved in the
.UFO
file. The same holds for the peak area; it is always the PBC corrected value, and the net peak area before PBC is not saved in the
.UFO
file.
6.12.12.2. Multiple PBC Subtraction
If there are multiple PBC peaks under a peak, that peak is subject to multiple PBC subtractions.
The sum of the PBC net areas is simply the sum of individual PBC areas (for comparison, see
Eq. 129 for single PBC subtraction):
(136)
where LT is the live time, R
p_i
is the PBC count rate for the i-th PBC, and m is the total number of PBC peaks.
The total PBC uncertainty is calculated from the following (compare to Eq. 130):
(137)
where
σ absp_i
is the absolute uncertainty of each PBC peak in counts. After calculating N
p
and
σ
absp
for the combined PBC subtraction with multiple PBC the rest of the calculations can be applied the same way as for a single PBC (that is, all equations in this section except Eqs. 129 and 130 can be applied the same way for both single and multiple PBC subtractions).
305
