iSERIES Algorithm
Table 5 Sample Activity Range
Alpha 3 - 6.4
MeV
1
σ
σ %
95%
Range
Low
95%
Range
High
Glass Fiber Model LB5211 A-O
170
18
10.59 %
134
206
PTFE
16
4
25.00%
8
24
Glass Fiber Model LB5211 A-O
89
13
14.61%
63
115
PTFE
4
2
50.00%
0
8
Using a 95% confidence interval (2 standard deviations) we can easily see that the
range of Glass Fiber Model LB5211 A-O was from 134 to 206.
Manual Gain Adjust
The gain calibration is critical for the algorithm to work properly. For the gain
calibration to work correctly, the system must be able to place the peak channel of the
Am-241 standard in channel 133.
In the case of Figure 17, the gain had been set too high. The blue peak is actually from
Po-214 (7.68 MeV) and should be in a considerably lower channel than what is
displayed. In this case, the algorithm is misidentifying the Po-214 peak as Po-212 at
8.78 MeV. Step 2 of the algorithm was “Use the Peak Shape of
212
Po (ThC', 8.78 MeV)
to derive correction for the
212
Bi (ThC, 6.05 MeV) contribution” so the misidentified
peak is used to subtract the Bi-212 peak that does not exist. Figure 17 shows the
disastrous effect of this with the red “negative peak” between 5-5.6 MeV.
iMatic Automatic Counting System User's Manual - 9239221K
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