
6.4 Threat Material Detection with PFNA
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plastic bombs, it is C
6
N
6
O
6
H
6
. Fermi argued that the presence of nitrogen is the
“explosive signature” and should be detected via 10.8 MeV γ’s emitted by ther-
mal neutron capture in
14
N. Westinghouse researchers followed his idea by a
development program that was abandoned 10years and $100 million later with
the admission: “We developed a nitrogen detector, not an explosive detector.”
One cubic meter of air contains nearly a kilogram of N
2
. Qualitatively detecting
the mere presence of one or more elements of the explosive does not make an
explosive detector.
Since there are no excited states of H, the ...