Buffle Landmines Talk

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

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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.

Buffle Landmines Talk

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