GAMMA RESONANCE TECHNOLOGY FOR
DETECTION OF EXPLOSIVES, REVISITED
L. Wielopolski1, P. Thieberger2, J. Alessi2, J. Brondo3, D. Vartsky4, and J. Sredniawski5.
1
Environmental Science Department, 2Collider and Accelerator Department, Brookhaven National
Laboratory, Bldg. 490D,Upton NY11973, 3Scientific Innovations Inc., NY, 4Nuclear Research Center
Nahal Soreq, Israel, 5Advanced Energy Systems Inc., NY.
The physical principles of the gamma nuclear resonance absorptiometry have been laid down quite
sometime ago and have been used in many laboratories for studying nuclear structure. In the late
eighties and during the nineties it become apparent that gamma nuclear resonance methodology
can be implemented for elemental analysis in industrial environment. Specifically extensive work
has been published for detection of nitrogen. However, this progress was hampered by lack of
intense gamma sources that would interact resonantly with nitrogen. Recent advances in
production gamma resonance beams justify revisit of the Gamma Resonance Technology as a
viable tool for explosives and drug interception in large cargo containers.
techniques to measure lifetimes of the nuclear
levels shorter than ~10-10 sec. Metzger provided
in his work a comprehensive summary of the
nuclear fluorescence principles that include
references to earlier works [3]. Sowerby
presented elemental analysis in bulk samples
using gamma resonance techniques [4-6].
Multiplicity of gamma lines for gamma-ray
resonance absorption was described in Ref. 7.
The principles and its current status are
presented below.
INTRODUCTION
With the coordinated attacks against the World
Trade Center in New York and the Pentagon in
Washington on September 11, 2001, the threat
of terrorism rose to the top of the country’s
national security and law enforcement agendas.
One of the many federal efforts calls for
increased vigilance and control on the
international border crossings to prevent
infiltration of explosives, biological, chemical
and nuclear weapons. The situation of particular
concern is that of large containers or palatalized
cargo, that enter through our airports, seaports
and by land. A small fraction of these are
currently interrogated using simple gamma-ray
systems using Cs-137 or Co-60 radioisotopes.
However, these methods that provide only total
mean mass attenuation without any additional
information are highly unsatisfactory for
comprehensive inspection of sealed containers
or cargo.
Two leading methods emerging for large cargo
inspection capable of providing specificity
through elemental analysis of the cargo content
are that of Pulsed Fast Neutron Analysis
(PFNA) [1], and Gamma Resonance Technology
(GRT) [2].
Of these two methods GRT is being briefly
reviewed here. The basis for GRT also referred
to as resonance fluorescence in nuclei was laid
down during the thirties and forties to develop
THE GRT METHOD
The processes of gamma interactions with
matter include photoelectric effect, which at
high gamma-ray energies is negligible,
Compton, pair production and nuclear resonance
absorption and scattering over very narrow
energy intervals. In the case of resonance
interaction with nitrogen these processes are
qualitatively depicted in Fig. 1. In the top
section the flat atomic cross section is shown
together with the resonance cross section, which
is about 149 eV wide. Since the total beam
width is about 500 eV with a flat distribution as
depicted in the second panel in Fig.1its atomic
cross section is flat. Such a beam in the absence
of nitrogen will undergo a uniform attenuation
as depicted in the third panel the resonance
region being unaffected. However, in presence
of nitrogenous material there will be additional
CP680, Application of Accelerators in Research and Industry: 17th Int'l. Conference, edited by J. L. Duggan and I. L. Morgan
© 2003 American Institute of Physics 0-7354-0149-7/03/$20.00
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proportional to the nitrogen concentration.
Moreover by rotating the object a 3-dimensional
distribution of the total density and of the
nitrogen density can be mapped.
GAMMA RESONANCE SOURCE
Table 1.
Elemental analysis via
(p,gamma) reactions on a single
element targets.
Element
Target
14
13
16
27
N
O
35
Cl
40
Ca
C
Al
34
S
39
K
Ep
Eg
(MeV) (MeV)
1.76
1.91
1.89
2.04
9.17
7.12
8.21
10.32
The best method of obtaining gamma-ray
beams with high intensity and energy resolution
combined with energy variability is provided by
the (p,gamma) reaction. In this reaction
choosing the scattering angle between the
gamma beam and the proton beam can vary the
gamma beam energy. Example of single element
targets for analysis of N, O, Cl, and Ca are
shown in Table 1.
These single element targets are specifically
tuned for a single element analysis, although in
some cases it might be possible by varying the
energy to achieve resonance conditions with a
different element. However layered and
composite targets can be designed for multielemental analysis. These types of targets were
not constructed yet [8].
This process of production of resonance
gamma radiation requires low energy (~2 MeV)
high intensity, in the range of 10 mA, proton
beam accelerators. Although various types of
accelerators such as Electrostatic (Single ended
or Tandem), Cyclotrons, RFQ linacs and
Induction linacs will produce proton beams with
suitable energy, the requirement for high beam
intensity and specific beam parameters limited
in the past the deployment of a system. The
required accelerator and beam specifications are
outlined in Table 2.
Figure 1.
Schematic depiction of the
nuclear resonance interaction of gamma- ray
beams with nitrogenous and non-nitrogenous
material.
attenuation due to gamma nuclear resonance that
is shown as a notch in the fourth panel in Fig. 1.
This difference is measured with resonance
detectors that exhibit a cross section as that
shown in the bottom panel of Fig. 1. Placing
resonance detectors behind the object and using
pulse shape discrimination will allow the
simultaneous measurements of the total
attenuation due to atomic interaction and the
specific resonance (nitrogen) attenuation that is
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Table 2.
Accelerator and proton beam specifications
COUNTER-TERRORISM
DESIGN SPECIFICATIONS
Nuclear
Reaction
Thin Sheet
Plastic H. E.
(N)
Bulk Explosives
(N & Cl Based)
13
13
C(p,γ) 14N
34
C(p,γ) 14N
S(p,γ) 35Cl
COUNTER-DRUG
Bulk Drugs
(N-Density)
13
C(p,γ) 14N
Bulk Drugs
(N & CL Density)
13
34
C(p,γ) 14N
S(p,γ) 35Cl
Ion Source
Current (mA)
12 (H-)
12 (H-)
12 (H-)
12 (H-)
Source Emit. 90%
(π mm-rad)
≤0.5
≤0.5
≤0.5
≤0.5
Beam Energy
(MeV)
1.75
1.75
1.89
1.75
1.75
1.89
Beam Spread (42)
(keV)
<25
<25
<12
<25
<25
Total Emittance
(π mm-mrad)
≤1.8
≤1.8
≤1.8
≤1.8
Divergence 4σ
(mrad)
≤12
≤12
≤12
≤12
Beam Current
(mA)
≥10
≥12.5
≥10
≥12.5
Target Spot Size
(cm)
0.6 x 2.4
0.6 x 2.4
0.6 x 2.4
0.6 x 2.4
Target
Coatings
13
C
13
34
C
S
13
C
13
34
C
S
Detector FOV
(deg)
53
53
53
53
Spatial Resolution
(cm)
0.5
5.0
5.0
5.0
Throughput
(bags/hr)
≥450
≥450
≥30
≥30
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RESULTS
a
Three major experiments with low intensity
proton accelerators were performed to detect
nitrogen in explosive simulants using resonance
detectors. First one was performed at Los
Alamos in 1977 to detect simulants in a LD-3
container. The set-up and the resulting image of
the total density and nitrogen density are shown
in Figs. 2a and b.
a
b
b
Figure 3.
Set-up of nitrogenous
and non-nitrogenous materials, a.
Nitrogram clearly distinguishes
between these two materials; a twoinch brick is transparent to
resonance radiation.
The third experiment was performed at
McMaster University where a roast pot was
imaged for nitrogen for medical purpose [9,
10]. Experiments were also performed using
BGO detectors.
Figure 2.
Six simulants placed in a LD3 container, a, and whole cargo and nitrogen
density are shown in, b. Cathegory A
explosive is clearly detectible. Ref. 2.
DISCUSSION
A second set of experiments was performed at
Birmingham University by the same team from
Nahal Soreq in Israel as in Reference 2. In these
experiments use was made of a lead brick, metal
tools, a thin 5 mm simulant and vials with
various concentrations of nitrogen in the range
from 0.1 to 10 % by weight. The results from
these measurements are presented in Figs. 3a
and b.
Developments in the electrostatic accelerator
technology in the last ten years brought once
again the GRT to the surface as a viable
approach for large cargo containers interrogation
tool at the nation air- and seaports. The currently
proposed PFNA method has some shortcomings
that might be socially unacceptable. Furthermore
a recently published assessment of the
practicality of the PFNA system for aviation
security that uses relatively small standardized
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7. Van’T Westende APM., Lancman H., and
Van Der Leun C., The Resonance GammaRay Absorption Method. NIM 151, 205-210,
1978.
8. Gardner SD., Frankle CM., and Berman
BL., March, 1944 Status Report Nuclear
Resonance Fluorescence Study, LANL,
NIS6-94:341SDG, 1994.
9. Vartsky D., Goldberg MB., Bar D.,
Goldschmidt A., Feldman G., Sayag E.,
Katz D., Stronach IM., Stark JW., Prestwich
WV., McNeill FE., and Chettle DR.,
Gamma
Resonance
Absorption:
An
Alternative Method for In Vivo Body
Composition Studies. Eds. Yasumura S,
Wang J., and Pierson Jr. RN. In Vivp Body
Composition Studies, Annals of the New
York Academy of Sciences, 904, 236-246,
2000.
10. Wielopolski L., Vartsky D., Pierson Jr. RN.,
Goldberg M., Heymsfield S., Yasumura S.,
Melnychuk ST., and Sredniawski J, Gamma
Resonance Absorption New Approach in
Human
Composition
Studies.
Eds.
Yasumura S, Wang J., and Pierson Jr. RN.
In Vivp Body Composition Studies, Annals
of the New York Academy of Sciences, 904,
229-235, 2000.
11. Griffin PJ., chair of the panel on Assessment
of the Practicality of Pulsed Fast Neutron
Analysis for Aviation Security. National
Security Council, National Academy Press,
Washington, DC. 2002.
LD-3 containers, found serious limitations in the
PFNA capabilities [11]. The major ones being
the requirement for a separate building due to
residual induced activity build-up, uncertain
diagnostics in one third of the LD-3 containers
and effect of hydrogenous cargo, e.g., food, in
which neither Category A nor Category B
explosives could be reliably detected.
In light of these serious limitations,
notwithstanding the multi-elemental capabilities
of the PFNA, 2GRT should be vigorously
developed and tested for interrogation of large
cargo containers. Initial results presented are
very encouraging and tests are required to
confirm the viability of the method for large
cargo containers.
REFERENCES
1. Gozani T., Understanding the physics
limitations of PFNA – the nanosecond
pulsed fast neutron analysis. NIM in Physics
research B99, 743-747, 1995.
2. Vartsky D., Goldberg MB., Engler G.,
Goldschmidt A., Feldman G., Bar D., Sayag
E., Katz D., and Krauss RA, Gamma-Ray
Nuclear Resonance Absorption (gammaNRA) for Explosive Detection in Air Cargo.
In Applications of Accelerators in Research
and Industry CP475, eds. Duggan JL and
Morgan IL., 687-690, 1999.
3. Metzger FR. Resonance Fluorescence in
Nuclei, in Progress in Nuclear Physics Ed.
Frisch OR., Volume 7, 53-88, 1959.
4. Sowerby BD., A New Method of Element
Ana;ysis
Using
Nuclear
Resonance
Scattering of Gamma Rays, NIM, 94, 45-51,
1971.
5. Sowerby BD., A Comparison of Gamma
Ray Resonance Scattering Techniquesnfor
Borehole Analysis, NIM, 108, 317-326,
1973.
6. Sowerby BD, Ellis Wk., and GreenwoodSmith R., Bulk Analysis for Copper and
Nickel in Ores Using Gamm-Ray Resonance
Scattering, in Nuclear Techniques and
Mineral Resources, Proceeding of a
Symposium in Vienna7-10 March 1977,
IAEA-SM-216/4, 499-521, 1977.
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