ORTEC
®
Fission Meter
®
(FM-P3) Portable Neutron Source Identification System
931026D / 060118
20
Figure 24. Email with 2A.log File Attached.
3.4.3
Graphing the Data
Once you have downloaded the Characterization Mode data, it can be displayed on the instrument in two
very informative ways.
The first is the multiplicity plot (Figure 25), showing a Poisson (purely random) distribution matched in mean
count to the data. Deviations from a Poisson distribution could indicate non-cosmic neutrons. For instance,
when the static mode’s
N-Cosmic Near CPS
parameter indicates a nearby source, and Characterization Mode
data are subsequently collected from the source and graphed, the data will be clearly more correlated than
the expected background shape, and far more correlated than a Poisson distribution. This excess in
correlation is recognized by the Fission Meter software when you make a near measurement.
The second plot is the neutron lifetime (Figure 26), which can aid in detecting moderation material such as
polyethylene shielding.
Figure 25. Multiplicity Plot.
