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How the Applied Physics Institute is developing technologies for the War on
Terror.
by Phil Womble
WKU's Applied Physics Institute is developing technologies to help the
Nation's war on terror. These technologies will help law enforcement
officers or soldiers to detect explosives or other contraband materials
such as drugs in a non-destructive and non-intrusive manner.
In the past, x-ray systems have been used to detect explosives.
Operators of these systems look for suspicious shapes and wires. However,
terrorists have become sophisticated in their methods of hiding
explosives. Explosives can be differentiated from innocuous materials and
from other contraband materials through the examination of the elemental
content. In particular, the ratios of chemical elements have been used to
perform this differentiation with great success.
Pulsed Elemental Analysis with Neutrons (PELAN) is a system that
determines the elemental content of objects in an automatic manner and was
designed for the characterization of explosives. The system consists of a
pulsing d-T neutron generator and a bismuth germanate (BGO) gamma-ray
detector. PELAN is a small man-portable device, composed of a suitcase
that contains the necessary power supplies for the neutron generator and
the data acquisition system, and of a probe which is placed next to the
object under interrogation (see figure below). The probe contains the
neutron generator tube (upper horizontal tube in the figure), the BGO
g-ray detector (lower horizontal tube), and the necessary material to
shield the detector from the neutrons (vertical tube). The total mass of
the probe and suitcase is less than 45 kg.
 In principle, a neutron impinging on an object can initiate one of
several nuclear reactions with the chemical elements of which the object
is composed. In most of these cases, as a result of these reactions, g
rays are emitted with characteristic and distinct energies. These g rays
are like the "fingerprints" of the elements contained in the
object. By counting the number of g rays emitted with
a specific energy
(e.g. the g rays of sulfur), one can deduce the amount of the element
contained within the object. In the case of an object that is hidden among
other innocuous materials, the identification takes place through the
correlation of various chemical elements observed, coupled to the
information about the innocuous material itself.
The PELAN was invented by Dr. George Vourvopoulos, Director of the
Applied Physics Institute. The two people chiefly responsible for its
development are WKU Alumni, Dr. Phil Womble and Jon Paschal. As
undergraduates Paschal and Womble worked closely with Vourvopoulos on
applied nuclear research.
 PELAN has undergone three field trials since 1999. The first field
trial concentrated on PELAN's ability to detect explosives. PELAN was
ability to identify threats with 100% success. The other two field trials
concentrated on detecting chemical warfare (CW) agents such as mustard
gas, lewisite, and nerve agents such as sarin (sarin was used in the Tokyo
subway attack several years ago).
The first CW agent trial took place in May 2001 at Poellkapelle,
Belgium at the request of the Belgian military. PELAN examined French,
German, and British shells from World War I. Despite nearly a century
beneath the soil, these weapons still posed a threat to the people of
Belgium.
In the Belgium tests , PELAN was not only able to identify whether CW
agent was present but also to identify the type of CW age. Further tests of
PELAN are planned for PELAN in 2002, and commercial prototypes of the
PELAN are expected to be distributed to bomb squads in early 2002.
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