783620H / 1013 6. ANALYSIS METHODS
where:
L pk
L
Lo
L
Hi
= The peak width, L
Hi
! L
Lo
+ 1.
= The background width on the peak’s low-energy side
= The background width on the peak’s high-energy side
For special cases, see Section 6.17.7.1.
6.17.3. Other Quantities in ISO NORM
Starting from the model that uses the net peak area as the measurand, the GammaVision equivalent of the other quantities required in ISO NORM are defined in Table 16.
All parameters are expressed in units of counts. Note that GammaVision uses the term critical
level (in counts) for the ISO NORM term decision threshold; and the term MDA (in counts) for the ISO NORM term detection limit.
Table 16. Terminology Comparison: GammaVision vs ISO NORM.
GammaVision expression
ISO NORM expression Description
N
σ
N
N h
σ
Nh
N
CL
N
MDA
N < N
CL
N > N
CL
N
<
N
> y u(y)
í
u(
í)
y* y
# y < y* y
$ y*
y
=
y
<
Net peak area
Uncertainty of the net peak area
Best-estimate of the net peak area
Uncertainty of the best-estimate peak area
Critical level or decision threshold
The MDA or the detection limit
Peak area less than the critical net peak area
Peak area greater than the critical net peak area
Lower limit of the net peak area
Upper limit of the net peak area
6.17.4. Conversion from Counts to Activity
On the GammaVision analysis reports, reported quantities in activity units can be obtained by a simple conversion factor,
ξ, from the counts:
313
GammaVision
®
v7 (A66-BW) 783620H / 1013
(146)
where:
TDC
= decay corrections, incorporating DDA, DC, and DDC as defined in
Sections 6.10.1 through 6.10.3.
Mult
= multiplier entered on the System tab.
RSF
LT
ε
E
Br
= random summing correction factor (Section 6.11).
= live time.
= detector efficiency at energy E (Section 5.3.3); this efficiency factor is stored in the
.CLB
record of the
.SPC
spectrum file.
= peak branching ratio from library.
GeoFac = geometry correction factor as described in Section 6.10.5.
A c
Div s
= attenuation correction (Section 6.10.6.1).
= divisor entered on the System tab.
= sample quantity entered on the System tab.
If reporting total sample activity is requested in GammaVision, then:
(147)
Specific conversions from counts to activity units are performed on the following quantities:
! Peak Activity:
(148)
! Best Estimated Peak Activity:
(149)
! Uncertainty in the Peak Activity and Best Estimated Peak Activity:
(150)
(151)
314
