Defense Intelligence Reference Document Inertial Electrostatic Confinement Fusion

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rays which can be extracted through a special port (requires a thin low-Z window for
transmission). This can be viewed as a small scale soft source for individual laboratory
studies such as done at various large scale national laboratories like ANL, BNL, and LBL
(synchrotron "light sources"). However, this use has not progressed much past the
initial laboratory studies.
The cylindrical geometry offers a unique configuration for security inspection
applications. To illustrate this we next consider a design proposed for such a system.
INTEGRATED X-RAY /NEUTRON SOURCES
This integrated inspection system was proposed by G. Miley, et al., in Reference 5.1. It
incorporates combined 2.5- and 14-MeV IEC neutron sources and an IEC x-ray source.
Such neutron sources have already been described, but some comments about the x-
ray version are worthwhile. The cylindrical IEC, like the spherical one, can be converted
to an attractive tunable x-ray source with minimum alteration of the apparatus. X-ray
operation involves reversing electrode polarities and adding electron emitters along the
vessel wall. Hydrogen gas is substituted for deuterium since in this configuration the
main function of gas ions is to provide electron Bremsstrahlung emission. Intense
emission is concentrated in a small volume surrounding the central axis due to the high
electron density formed there. The resulting x-ray energy spectrum is peaked at an
energy equivalent to about two-thirds of the applied voltage. In the inspection station,
a voltage around 120 kV is employed to obtain ~SO-kV x-rays with some distribution of
energies above and below this mean value. X-ray production is spread along the axis
over a long line-like region in the IEC providing broad area coverage for imaging,
consistent with the broad coverage of the companion IEC neutron sources.
Consequently, the basic concept of the integrated inspection unit is to combine IEC
neutron and x-ray sources plus appropriate detectors into a single "package". This
combination expands the range of elements that can be detected during a single scan
and incorporates x-ray imaging with the 3-D detector array for NAA to obtain improved
identification of the shape and location of suspected objects in a container. In cases
where the object is too large to allow good x-ray penetration, information is still
obtained from the 3-D NAA detector array.
Nuclear and Chemical Explosive Detection Techniques
Most current inspection systems concentrate on x-ray imaging. This interrogation relies
on the photoelectric effect or Compton Scattering Imaging (CSI). It provides good
localization and some geometric information for higher Z materials. The NAA technique,
including both thermal neutron analysis (TNA) and fast neutron analysis (FNA), are
powerful methods for detecting certain types of explosives. Basic elements such as
oxygen, carbon, and chlorine present in the explosives can be identified through the (n,
n'y) reaction initiated by fast neutrons. The gamma rays produced in the reaction are
characteristic of elements being interrogated. Another basic element in many
explosives, nitrogen, is usually measured through (n, y) reactions initiated by thermal
neutrons. Either steady-state or pulsed sources can be employed for TNA. However,
increased sensitivity can be obtained with pulsed FNA (PFNA). This method uses a
pulsed high-energy neutron source and the time-of-flight (TOF) diagnostics to reduce
the "noise" effect resulting from scattered neutrons and x-rays.
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