iSERIES Algorithm
Sample Analysis Delay
The
i
SERIES is designed with multiple alpha counting regions. Radon daughter RaA
(Po-218) has energy of 6.0 MeV with half-life of 3.05 minutes. Mirion Technologies
(Canberra) recommends aging each sample for 10 minutes prior to the start of the first
analysis. Practically speaking, this limitation may only apply if the full alpha (Cm-242,
Cm-244) region is being used but the recommendation still holds for the other regions
as well.
Figure 11 Radon and Thoron Decay
Currently, there are no documented cases of a user getting an incorrect result strictly
from counting a sample too soon. In practice, the 10 minute aging time may be a
theoretical rather than a practical limitation.
Count Time
The sample analysis time should be set to no less than 10 minutes for the algorithm to
work properly. As counter intuitive as it sounds, the more radon/thoron present the
better the fitting routine will work.
Users have reported that the most accurate results come from counting a sample for 10
minutes three times and averaging the results of the three measurements. Note: this
methodology has not been validated by Mirion Technologies (Canberra).
iMatic Automatic Counting System User's Manual - 9239221K
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