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7/27/2019 Buffle Landmines Talk
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Detection of
Anti-Personnel Landmines
using Neutrons and Gamma Rays
Andy BufflerPhysics Department
University of Cape Town
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some landmine statistics . . .
> 60M abandoned in > 70 countries
(mainly small (< 300 g) plastic APM)
> 25k civilians killed annually
> 25k maimed annually
(mostly women and children)
centuries will be required to deal with this
problem unless the technology is improved greatly . . .
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some good news too . . .
the Ottawa treaty (1989) . . . .
aims to stop proliferation of landmines
more resources are now being directed towardsdeveloping methods for the detection and removal
of landmines and unexploded ordinance (UXO)
good research communication and regular
international conferences
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Some typical landmines and UXO
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anti-tank (ATM)
anti-personnel (APM)
Typical masses: ~ 5 kg (ATM); < 300 g (APM).
Plastic casing. Metal content often < 10 g.
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Detection (or destruction) of landmines
A) Established methods (in use already)Mechanical methods (flails and rollers to smash or detonate)
Metal detection (by electromagnetic induction) EMI
Ground-penetrating radar (recently introduced) GPRSniffer dogs
Probing sticks
Note:
all are methods developed primarily for military use
sensitivity of EMI sensors to metallic debris (eg shrapnel)can slow down demining operations
a second (confirmation) sensor of another type is usually
needed to discriminate against metal debris when EMI is
used as the primary (sweep) sensor.
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B) Some new (emerging) methods
Infra-red
X-ray back-scatter
Nuclear quadrupole resonance (NQR)
Laser-induced breakdown spectroscopy (LIBS)Smart prodders
Acoustic sensors
Artificial noseRats, bees, elephants, . . .
Neutrons and gammas
why neutrons and gammas ?
good penetration into the soil
capability to identify elements via nuclear interactions
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Differences between military and humanitarian demining
Military HumanitarianObjective . . . . . . minefield breaching complete clearing
Execution time . . minimum whatever it takes
Resources . . . . . . large small
Communication . . secretive free
Deep APM. . . . . . unimportant must be cleared
Removal efficiency > 90% > 99.6%
Casualty rate . . . . < 10% Nil
Established methods (A) meet the military requirements.
Humanitarian demining will probably require a multisensor
system incorporating one of the A-methods as the primarysensor and several confirmation sensors (A or B).
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SCHIEBEL ATMID (All Terrain Mine Detector)
a typical portable
(hand-held) metaldetector.
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The IAEA Coordinated Research Project
onNuclear techniques to aid humanitarian demining
(see IAEA Bulletin, 43/2/2001)
with participants from 18 countries -
Australia Austria Canada
Croatia Egypt Germany
Hungary Italy Japan
Netherlands Russia Slovakia
Slovenia South Africa Sweden
UK USA Vietnam
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New methods for landmine detection based on nucleartechnology are being investigated by means of:
computer simulations; laboratory experiments; and
field tests.
the investigations include consideration of factors
such as different soil types, environments and water
content.
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methods under study include . .
neutron-induced gamma emission
neutron moderation
neutron and gamma attenuation
fast neutron backscattering
gamma backscattering
gamma-gamma coincidence imaging
some examples ...
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Neutron-induced gammas (to detect explosives)
(studied by groups in 8 countries)
prompt . . . . . . . . . . . . (n,n), (n,x) . . . . (ns)
thermalization-delayed (n,) (s)neutron activation . . . . A(n,x)B C + (ms)
Different chemical elements are identified by means of theircharacteristic -spectra. Explosives are then identified from
elemental concentration ratios (H:C:N:O).
Example 1:
PELAN - Pulsed ELemental Analysis using Neutrons
(University of Western Kentucky and SAIC, USA)
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PELANd-T neutron generator (14 MeV n)
Gamma spectrometer (BGO 76 mm diam x 76 mm)
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Gamma rays
Detector
Mine
Pulsed neutron
generator
Neutrons
Overburden
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PELAN duty cycleFast Neutrons
Thermal Neutrons
Time
Neutron
Flux
10-15 S 80-100 S
Reaction (n,n), (n,p) .. (n, ) (n, ), (n,p) ..
Gammas Prompt Prompt Delayed
Elements C, O, .. H, S, Cl, Fe, N .. O, Na, Al, Si, P
Pulse height spectra from the BGO detector of PELAN
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478 keV, B
844 keV, Al
2223 keV, H
4438 keV, C
6129 keV, O
478 keV, B
844 keV, Al
2223 keV, H
6129 keV, O
7638 keV, Fe
Pulse height spectra from the BGO detector of PELAN
[prompt window (15 s)] [delayed window (100 s)]
Spectra are unfolded to determine element ratios
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August 2003
Preliminary PELAN results on AT mines
Probability of Detection : 97%
Probability of False Alarm : 10%
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Neutrons-in gammas-out
Example 2:
Nanosecond Neutron Analysis (NNA)(V G Khlopin Radium Institute, St Petersburg, Russia)
incorporates neutron tagging by the associated particletechnique using the reaction 3H(d,n)4He
a dual-sensor system has been developed withsweep sensor . . GPR
confirmation sensor . . . NNA
LOCALIZATION SENSOR
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LOCALIZATION SENSOR
Modulated Continuous-Wave Radar
Determines size, shape, and dielectric characteristics of objects
hidden in soil, concrete etc.
LOCALIZATION SENSOR
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LOCALIZATION SENSOR
Test measurements in strongly absorbing medium
Electricallength[cm]
Teflon cylinder ( 7 cm 4 cm) placed under 4 cm layer of sand(humidity 10% by weight)
7 cm
Surface of sand
4 cm
Shift along the scanning line [cm]
IDENTIFICATION SENSORIDENTIFICATION SENSOR
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Prototype device based on DT neutron generator with builtPrototype device based on DT neutron generator with built--inin
ninenine--segmentsegment --detectordetector
Nine-segment
detector of alpha-
particles built into the
neutron generator
Prototype of the NNA device for detectionof hidden hazardous objects based on a
portable neutron generator
IDENTIFICATION SENSORIDENTIFICATION SENSOR
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IDENTIFICATION SENSORIDENTIFICATION SENSORExperimental results for Dummy Land Mine (DLM 2.3) and calculated response
functions to carbon, oxygen and nitrogen. DLM2.3 was under 1cm layer of dry sand.
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
0.12
Experimental Actual
C/O 1.5 0.2 1.16
C/N 5.6 1.7 4.9
experimental spectrum of DLM2.3
experimental background
contribution of carbon
contribution of oxygen
contribution of nitrogenbest approximation
Countrate[/(sec100keV)]
E[MeV]
3 4 5 6 7
-2
0
2
Distance[]
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Gamma-ray Imaging
PACSI
Primary detector
Secondary
detector
e+ source
MINE
James Tickner et al.CSIRO Minerals
A gamma-ray camerathat takes 3D images
of objects that canonly be viewed fromone side.
10 cm
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PACSI Simulation results
Simulation of AP mine buried 100 mm deep in soil
Horizontal slice through centre of mine
L d i d t ti i t d ti
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Landmine detection via neutron moderation(based on detection of a hydrogen anomaly)
(under study by groups in 10 countries)
some of the devices developed are . .DUNBLAD (Netherlands)
DIAMINE (Italy & Croatia)
NO-NAME-YET (Hungary)HYDAD (South Africa)
Example:HYDAD landmine detectors (UCT)
Frank Brooks and Andy Buffler
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HYdrogen Density Anomaly Detection
Why a hydrogensignature?H in some explosives andplastics . . .
PETN RDX NylonTNT C-4 Acrylic Polyethylene
. . . . . . . . .
0 20 40 60 80
atom percent H
HYDAD
HYDAD H (hand held system)
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HYDAD-H (hand-held system)
Detector (3
He or10
BF3proportional counter)
DLM (100 g TNT in 100 g acrylic cylinder)
d
Sand
AmBe or252Cf source
The detector is insensitive to
fast neutrons and gammas
emitted by the source but
responds efficiently to the
thermal and epithermal
neutrons that result from n-pscattering in DLM.
Works well ford< 10 cm in dry sand.Not suitable for use on very wet sand.
HYDAD-H prototype
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HYDAD-H prototype
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HYDAD-H
prototype
ready for hand-heldoperation . . .
with batteries, powersupplies & electronics
attached to the belt
fastened around the
operators waist
HYDAD H i l
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-15 -10 -5 0 5 10 1510
100
1000
-15 -10 -5 0 5 10 150.1
1
10(b)(a)
Countspersecond
x (cm)
Beeps
persecond
x (cm)
HYDAD-H signals
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HYDAD movies : see www.phy.uct.ac.za/hydad
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V hi l t d HYDAD t f d APM
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Vehicle-mounted HYDAD system for deep APM
Detector
DLM2Source
Pipe
z
d
a Sand
r
The empty pipe is driven
into the ground at each point
where the primary sensor
showed a positive response.
The source and detector arebrought into position after
this is done. Count rate is
measured asf(r, z, ).
is the angle of rotation of
the detector about the pipe. HYDAD-VM
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Neutron and gamma attenuation method
the HYRAD detector . . .
(HYdrogen RADiography)
senses the hydrogen content of APM by means of
neutron and gamma-ray transmission radiography
similar to the neutron-gamma transmission technique
neugat, of Bartle et al.
and others !
HYRAD
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The count rates for n and are given by:
Nn = nNon exp(-n r)
N
= No exp(-r)
Their ratio isR =Nn/ N = nNon /Noexp {(-n)r}
If
= n (for sand) thenR is independent ofrand of
density variations in the sand.R may change if an object
M displaces sand between S and D.R decreases if M is alandmine and increases if M is a high-Z object.
r
S D
M
S - neutron and gamma source
D - NE213 detector (with PSD)M - landmine
S and D are mechanically coupled
sand
furrows
vertical section
3 x NE213A test of HYRAD
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x
d
DLM2 Lead disc
The source and 3 detectors are
scanned synchronously alongx tolocate maxima & minima inR.
minima
maxima
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Conclusion
Neutron- and gamma-based methods for landmine
detection have now reached a level of developmentat which they are ready for field testing.
A convincing success in field tests will be requiredin order for detectors of this type to be considered as
components of future multisensor mine detection
systems.