Amar Sinha

Neutron and X-ray Physics Facilities Bhabha Atomic Research Centre,

Trombay, Mumbai

Detection of explosives, narcotics and Detection of explosives, narcotics and

nuclear materials using neutronsnuclear materials using neutrons

About this talkAbout this talk

This talk is about role of nuclear This talk is about role of nuclear sciences in meeting challenges of sciences in meeting challenges of counter terrorismcounter terrorism

This talk is about how the nuclear This talk is about how the nuclear techniques which have been developed techniques which have been developed for basic research can be adapted for for basic research can be adapted for detection of explosives, narcotics or detection of explosives, narcotics or nuclear materialsnuclear materials

We will talk on efforts required for We will talk on efforts required for developing a system from lab scale to developing a system from lab scale to commercial scale commercial scale

This talk will also focus on main This talk will also focus on main constraints in developing such systems constraints in developing such systems –speed, ease of operation, footprint, –speed, ease of operation, footprint, cost etccost etc

CollaboratorsCollaborators

Mayank ShuklaMayank ShuklaP.S. SarkarP.S. SarkarYogesh KashyapYogesh KashyapTarun PatelTarun PatelTushar RoyTushar RoyAshish AgrawalAshish AgrawalSaroj BishnoiSaroj BishnoiRam Kumar PalRam Kumar Pal

Our activities at BARCOur activities at BARC

NeutronsNeutrons- - Reactors (CIRUS) -Reactors (CIRUS) -Tomography and Tomography and

Neutron Phase imagingNeutron Phase imaging Neutron Generator, D-D and D-TNeutron Generator, D-D and D-T Photoneutron sources Photoneutron sources Isotopic sourcesIsotopic sources Detector developmentDetector development Applications of neutrons Applications of neutrons

X-ray-X-ray- Imaging Beamline at Indus-II, RRCATImaging Beamline at Indus-II, RRCAT Phase imaging Phase imaging Tomography (Emission and transmission)Tomography (Emission and transmission) Medical Imaging Medical Imaging

TopicsTopics Brief description of existing methods Brief description of existing methods

Why neutrons?Why neutrons?

Various Neutron based methodsVarious Neutron based methods TNA- FNA – PFNA- PFTNA- API- TNA- FNA – PFNA- PFTNA- API- Neutrons for nuclear material detectionNeutrons for nuclear material detection

Purnima neutron generator- Purnima neutron generator- testing of concepttesting of concept Experiments with Purnima generator on Experiments with Purnima generator on

prompt gamma, tagged neutron, prompt gamma, tagged neutron, backscatteringbackscattering

Plan for portable systemsPlan for portable systems

What are the various steps in technology development?What are the various steps in technology development? (a) Mathematical modeling, (a) Mathematical modeling, (b) Modeling of detector responses(b) Modeling of detector responses © Spectrum analysis and deconvolution algorithm © Spectrum analysis and deconvolution algorithm (d) Laboratory Testing and their optimization(d) Laboratory Testing and their optimization (e) control and data acquisition systems(e) control and data acquisition systems (f) Assembling and testing (f) Assembling and testing (g) Development of decision making algorithms (g) Development of decision making algorithms (h) Field trials (h) Field trials (i) method to make portable systems for smaller vehicle –truck & car (i) method to make portable systems for smaller vehicle –truck & car (j) method to detect dirty bomb inside cargo(j) method to detect dirty bomb inside cargo (k) method for IED(k) method for IED ( l) Indigenous effort to develop API based portable neutron source( l) Indigenous effort to develop API based portable neutron source

Work at BARCWork at BARC

Limitations of neutron based methodLimitations of neutron based method

Conclusion Conclusion

Conventional methodsConventional methods

X-ray - X-ray - Generator for Generator for passenger baggage to passenger baggage to

Electron Linac based 9 Electron Linac based 9 MeV sources for cargoMeV sources for cargo

Single energy Single energy dual energy (gross low dual energy (gross low

and high density and high density discrimination)discrimination)

BackscatterBackscatter – –

GammaGamma

3D CT3D CT

TransmissionTransmission

Neutron based Neutron based techniquestechniques

Why neutron based?Why neutron based?

The key to distinguishing explosives from benign material is the use of elemental analysis.

X-ray Technique- insufficient

Problems with X-rayProblems with X-ray

Conventional technique -Conventional technique -X-rays X-rays based based methods for the detection of explosive methods for the detection of explosive materials are chemically blind. materials are chemically blind.

They can only determine They can only determine shapes and shapes and densitiesdensities of objects, leading to false of objects, leading to false recognition of material that may be recognition of material that may be physically similar to explosive physically similar to explosive compounds.compounds.

A piece of Semtex plastic explosive can be A piece of Semtex plastic explosive can be molded to look like a block of cheese or molded to look like a block of cheese or chocolate.chocolate.

Some other technologies can detect only Some other technologies can detect only surface of objects or based on close surface of objects or based on close examination of vapour near objects or too examination of vapour near objects or too cumbersome for mass screeningcumbersome for mass screening

Neutron based techniquesNeutron based techniques It is due to the limitations of conventional It is due to the limitations of conventional

techniques to meet such a challenge that other techniques to meet such a challenge that other more more definitive techniquedefinitive technique such as such as neutron based neutron based techniquestechniques are currently under active development are currently under active development for detecting such contraband materials inside for detecting such contraband materials inside vehicles, marine and air cargo containers vehicles, marine and air cargo containers

They can penetrate the shielding of cargo and to They can penetrate the shielding of cargo and to identify the composition of materials- identify the composition of materials- Of particular interest in the detection of conventional explosives are nitrogen, oxygen, carbon, and hydrogen

Neutron interrogation offers the possibility of measuring the elemental density of most elements in materials

Though not Though not as fast as x-ray screeningas fast as x-ray screening – but due to – but due to their capability to identify the chemical composition their capability to identify the chemical composition lead to lower false alarm ratelead to lower false alarm rate

They are being developed as They are being developed as second line of second line of confirmatory sensorconfirmatory sensor

Nuclear Physics behind the techniqueNuclear Physics behind the technique

The physical basis of these techniques is The physical basis of these techniques is well known to nuclear physicist. well known to nuclear physicist.

What has changed is adoption of such What has changed is adoption of such concepts in terms of reconfiguration of concepts in terms of reconfiguration of neutron sources and detector and neutron sources and detector and methodology for the purpose of explosive methodology for the purpose of explosive detectiondetection

Physical basis of detectionPhysical basis of detection

(n, n’)

(n,)

Emitted gammas are Finger print of element

SubstanceDensity (g/cm3)

%H %C %N %O%Cl

% Other elements

C/O

N/O

Cl/C

Cl/H

Benigns

Salt 0.77 0 0 0 0 60 40 0 0 0 0

Sugar 1.2 7 42 0 51 0 0 0.8 0 0 0

Sand 2.3 0 0 0 53 0 47 0 0 0 0

Water 1 11 0 0 89 0 0 0 0 0 0

Wood 0.62 6 47 0 44 0 3 1.1 0 0 0

Petroleum 0.87 14 86 0 0 0 0 0 0 0 0

Cement 2.3 0 0 0 35 0 65 0 0 0 0

PVC 1.32 5 38 0 0 57 0 0 0 1.5 11.5

Polyethylene 0.94 14 86 0 0 0 0 0 0 0 0

Fiberglass 1.7 3 46 0 35 0 16 3 1.3 0 0

Sea water 1.02 10 0 0 88 1.2 0.8 0 0 0 0.03

Explosives

PETN 1.76 2.4 19 17.7 60.8 0 0 0.3 0.3 0 0

TNT 1.63 2.2 37 18.5 42.3 0 0 0.9 0.4 0 0

Dynamite 1.18 4.2 14.8 18.5 62.4 0 0 0.2 0.3 0 0

C4 1.65 3.6 21.9 34.4 40.1 0 0 0.6 0.9 0 0

Narcotics

Heroin hydrochloride

0.87 6 62.1 3.5 19.7 8.7 0 3.2 0.2 0.1 1.5

Cocaine hydrochloride

0.87 6.5 60.1 4.1 18.8 10.4 0 3.2 0.2 0.2 1.6

Heroin 0.87 6.3 68.2 3.8 21.7 0 0 3.2 0.2 0 0

Cocaine 0.87 6.9 67.3 4.6 21.1 0 0 3.2 0.2 0 0

Elemental composition of common substances narcotics, explosives, and chemical weapons

Chemical_weapons

Hydrogen cyanide 3.7 44.551.8

0 0 0 0 0 0 0

Mustard gas 5 30.2 0 0 44.6 20.2 0 0 1.5 8.9

Sarin 7.1 34.3 0 22.9 0 35.7 1.5 0 0 0

Substance Density (g/cm3)%H

%C %N %O %Cl % Other elements

C/O N/O Cl/C Cl/H

Characteristic gammaSignature

The technique one chooses is The technique one chooses is dependent on what you want to dependent on what you want to

detectdetect

Incident Neutron energy is important for some inelastic reaction

Different detection schemes have been Worked out –

(a) based on only capture(b) use Inelastic or both© use imaging to spatially localize the signal(d)other use time of flight

Which neutron Which neutron techniquetechnique

TNATNAFNAFNAPFTNAPFTNANRANRA………………..PFNAPFNAAPIAPI………………..

We focus on a few Methods

(a) (a) Thermal Neutron Analysis (TNA)Thermal Neutron Analysis (TNA)::

Basic principle of TNA

Isotopic source – 252Cf or even Am-BeIn fact this technique using 252Cf has been used extensively for interrogating parcels

Limitations –mostly qualitative–small parcels –where other background is minimal

TNA spectrum for Bag with and without small explosive

The main signatures used are derived from detecting the

- 4.43 MeV γ-ray from 12C-1.64, 2.31 and 5.11 MeV γ-rays from 14N-6.130 MeV γ-ray from 16O

(b)

© © Pulsed Fast-Thermal Pulsed Fast-Thermal Neutron Analysis (PFTNA)Neutron Analysis (PFTNA)

Being used for vehicle borne explosive detection UXO characterization landmine detection

(d)

ELECTRON LINAC BASED NEUTRON SOURCEELECTRON LINAC BASED NEUTRON SOURCE

BeTantalum

electron-photon- neutron

e

n

high energy electrons to produce photons

- Photons then produce neutrons through photo-neutron reaction-

We have helped Mangalore university design such a source based on microtron

Combined Neutron and Combined Neutron and

Gamma-Ray InterrogationGamma-Ray Interrogation

Ratio of neutron attenuation to gamma attenuation

(e)

Ratio of neutron to gamma attenuation

Device based on this concept is operationalAt Brisbane airport for air cargo scanning

NEUTRON RESONANCE NEUTRON RESONANCE

RADIOGRAPHYRADIOGRAPHY Uses energy Uses energy

selective radiography selective radiography unlike the previous unlike the previous technique which uses technique which uses white neutron source white neutron source and requires a and requires a variable energy variable energy neutron source to neutron source to extract information.extract information.

specific mapping of specific mapping of elements based on elements based on their resonance their resonance properties of their properties of their total interaction total interaction cross-sectioncross-section

Variable energy is produced using Variable energy is produced using d(d,n)3He reaction and energy selection is d(d,n)3He reaction and energy selection is made by varying production anglemade by varying production angle

(f)

Imaging Techniques?Imaging Techniques?

The ability to measure precisely elemental The ability to measure precisely elemental concentrations in an inspected object is necessary but concentrations in an inspected object is necessary but not sufficient condition for a successful inspection not sufficient condition for a successful inspection

systemsystem..

Simple detection of nuclear signature is not enough if the Simple detection of nuclear signature is not enough if the object being inspected has large volume. For large object object being inspected has large volume. For large object the information from contraband may be smeared due to the information from contraband may be smeared due to signal from surrounding constituents of the cargosignal from surrounding constituents of the cargo

If somehow the measurement can be localized inside the If somehow the measurement can be localized inside the volume of cargo, the determined elemental densities will volume of cargo, the determined elemental densities will represent the material composition at that very volume represent the material composition at that very volume element (voxel) and not an average over a larger volume. element (voxel) and not an average over a larger volume.

Improved S/N ratioImproved S/N ratio

Two schemes –PFNA and API

(g) Pulsed Fast Neutron analysis (PFNA)(g) Pulsed Fast Neutron analysis (PFNA)

PFNA –use of PFNA –use of pulsed pulsed nanosec beam nanosec beam directional directional monoenergetic monoenergetic beambeam

Producing pulsedNanosec beam Directional beam -requires large Accelerator -expensive

(h) Tagged Neutron(h) Tagged Neutron

(Associated particle Imaging)(Associated particle Imaging)

• It can provide 3D information about any volume by detecting gamma in coincidence with alpha in the DT reaction

• It can be used to detect explosives, narcotics etc in cargo

• It can be used to detect SNM in CARGO by detecting the fission gamma induced by burst of external neutron

• It can be used to detect SNM by use of correlation/coincidence techniques

This method has been extensively tested at a Port in Europe under a project named “EURITRAC”

EURITRACK –consotorium of EURITRACK –consotorium of

16 European Agencies16 European Agencies

Explosive detection Explosive detection technique using neutronstechnique using neutrons

We feel API method also called tagged Neutron Method has potential to be used in large cargo/container scanning which is of interest to us. We are coordinating with several agencies in evaluation of such system and for this reason we are evaluating several technologies including API system

Fissile material Fissile material DetectionDetection

Passive – coincidence -gammaPassive – coincidence -gammaActive interrogation- A variety Active interrogation- A variety

of signatureof signatureNeutron in- fission neutron outNeutron in- fission neutron out

Prompt and delayed – both carry Prompt and delayed – both carry signaturesignature

Neutron in – fission gamma outNeutron in – fission gamma out

Differential Die awayDifferential Die away

Tagged neutron coincidenceTagged neutron coincidence

Residual fissile material in waste stream Residual fissile material in waste stream Differential Die AwayDifferential Die Away

This technique is also used in Hull MonitoringThis technique is also used in Hull Monitoring

In reprocessing plant to monitor plutoniumIn reprocessing plant to monitor plutonium

Dirty Bomb

The background flux below 10 MeV to be ≈0.01 n/s.cm2 . One kilogram of weapon grade plutonium (WGP) emits 6.104 n/s following a Watt energy spectrum . Simple algebra shows neutron flux from the plutonium becomes over shadowed by the background beyond a distance of about 7 m. Standard scanning methods will not be able to detect such an amount of WGP in a sea container since 7 m is of the order of the dimension of the container.

Directional fast neutron ImagingDirectional fast neutron Imagingfor special Nuclear material (SNM)for special Nuclear material (SNM)

Substantial reduction of the background will be possible by using a fast neutron detector with imaging properties. The background rate within an opening angle corresponding to an angular resolution of 10o for example is reduced by a factor:

2

4128

tan 10

under the assumption of isotropy of the background. With such a direction sensitive detector the WGP can be detected above the natural background up to a distance of about 70 m.

Delft University of Technology - harbor of Rotterdam

Fast neutrons lose energy when penetrating hydro-Fast neutrons lose energy when penetrating hydro-carbon scintillator materials by interactions with protons carbon scintillator materials by interactions with protons and carbon nuclei. The recoil proton energy is released and carbon nuclei. The recoil proton energy is released as scintillator light and the collision kinematics uniquely as scintillator light and the collision kinematics uniquely defines the scattering angle of the neutron. The proton defines the scattering angle of the neutron. The proton track itself is too short to be observed. When the track itself is too short to be observed. When the scattered neutron experiences a second collision with a scattered neutron experiences a second collision with a proton inside the scintillator the direction of the original proton inside the scintillator the direction of the original incoming track can be determined see figure 1 incoming track can be determined see figure 1

Directional fast neutron ImagingDirectional fast neutron Imagingfor special Nuclear material (SNM)for special Nuclear material (SNM)

Two successive n-p elastic Two successive n-p elastic scatteringscattering

Determine:Determine: interaction positionsinteraction positions energy scattered neutron energy scattered neutron En’En’ direction scattered neutrondirection scattered neutron energy of the first recoil proton energy of the first recoil proton

p1p1 Determine the incident neutron Determine the incident neutron

energyenergy

Calculate scatter angle Calculate scatter angle Construct coneConstruct cone

Common direction on several Common direction on several cones points to the sourcecones points to the source

'1 npn EEE

p2

p1

n

n'

'n p nE E E 2sin p

n

E

E

Double elastic n-p scattering showing the basic kinematics of event reconstruction. If the full neutron energy is measured, the incident neutron direction is restricted to the mantle of a cone and an “event circle” can be drawn

: Schematic of the source-imaging fast-neutron detector. Reactions of two incoming neutrons are shown (tracks in green and blue). The small arrows show recoiling protons (in red). For simplicity only one light sensor (PMT) is indicated.

Working on Various steps in technology Working on Various steps in technology development?development?

(a) Simulation (a) Simulation -optimize parameter-optimize parameter (b) Laboratory Testing and their (b) Laboratory Testing and their

optimizationoptimization (c) Modeling of detector responses(c) Modeling of detector responses (d) Spectrum analysis and deconvolution (d) Spectrum analysis and deconvolution

algorithm algorithm (e) control and data acquisition systems(e) control and data acquisition systems (f) Assembling and testing (f) Assembling and testing (g) Development of decision making (g) Development of decision making

algorithms _neural network, Fuzzy Logicalgorithms _neural network, Fuzzy Logic (h) Field trials (h) Field trials (i) method to make portable systems for (i) method to make portable systems for

smaller vehicle –truck & car smaller vehicle –truck & car (j) method to detect (j) method to detect nuclear material in cargonuclear material in cargo ( k) Indigenous effort to develop portable ( k) Indigenous effort to develop portable

neutron sourceneutron source

Photograph of the Purnima neutron generator

•Cockcroft-Walton voltage multiplier

•300KV -10mA

Tritium Target

Ion source Dome High

Voltage Power Supply

Faraday Cup

BPM

Beam Steerer

Accelerating Tube

Turbo Molecular Pump

F

400 kV DCPower Supply

Ion Source Dome

Accelerating Column

Beam Steerer

BPM

Faraday Cup

Tritium Target

TMP

Neutron Generator at Purnima, BARCNeutron Generator at Purnima, BARC

Schematic of the Purnima Neutron Generator

Basic facility for testing before field application

StatusStatus

This generator is running in This generator is running in both D-D and D-T modeboth D-D and D-T mode

Safety committee has Safety committee has permitted us to operate it at 10permitted us to operate it at 107 7

n/s in D-T and 3x 10n/s in D-T and 3x 107 7 n/s in D-n/s in D-D modeD mode

However shortly we are going However shortly we are going to take a trial run in D-T mode to take a trial run in D-T mode upto 10upto 101010 n/s n/s

Graph of the Signal and background data in terms of channel versus counts. The Hydrogen peak at 2.22 MeV and the nitrogen photopeak at 10.829MeV are very clearly visible. Nitrogen single escape peak is also distinguishable. The data collection time was 1800 seconds. Urea (CO(NH2)2) : Molecular weight: 60.06 gm, Density: 1.33gm /cc: Composition: H—6.71%, C – 20%, N – 46.65% and O – 26.64%

Spectrum of Urea showing H and N capture lines

-Top curve with urea-bottom without urea

Experiments on PGNAExperiments on PGNA

Sample: Salt (NaCl)Sample: Salt (NaCl) The main aim to carry out the detection chlorine (Cl) The main aim to carry out the detection chlorine (Cl)

capture lines in salt is due to fact that chlorine based capture lines in salt is due to fact that chlorine based compounds form part of narcotics. Since Cl has more compounds form part of narcotics. Since Cl has more neutron capture cross-section (43b) than Na the neutron capture cross-section (43b) than Na the capture gammas of Cl are much more detectable than capture gammas of Cl are much more detectable than Na. In a data collection time of 1200 seconds we Na. In a data collection time of 1200 seconds we could detect 4 Chlorine photo-peaks and one of their could detect 4 Chlorine photo-peaks and one of their escape peaks. escape peaks.

Left graph shows the Chlorine peaks (labeled in MeV energy): Cl-6.619MeV and Cl – 6.11 MeV along with its single escape peak Cl’ – 5.599MeV and double escape peak Cl’’ – 5.08MeV. The right hand side graph shows the other Cl lines, 1.16MeV and 1.95MeV.

Graphite (6-8kg)sample was irradiated for Graphite (6-8kg)sample was irradiated for the detection of theprompt gamma the detection of theprompt gamma

4.439MeV from carbon element.4.439MeV from carbon element.We have observed the 4.439 as well as We have observed the 4.439 as well as

its first escape peakits first escape peak

100 200 300 400

104

105

Cou

nts

Channel Number

...Background...Graphite

C-4439C(3928-SE)

Aquisition Time=20 min

Prompt inelastic gammaD-T neutron

Similarly experiments with urea and water for nitrogen and oxygen detection have been done.

Developing Tagged NeutronDeveloping Tagged Neutron

(Associated particle Imaging)(Associated particle Imaging)

API method diagramAPI method diagram

DT (En=14 МeV)

Eα = 3.5 MeV

Time-of-flight for

14 МeV neutron:1 ns => 5.2 cm

Ability for 3D-imaging:

elemental analysis +

direction and depth

Sufficient improvement

for ratio effect/background

In the d + t reaction a neutron with energy of 14 MeV and an alpha particle with energy of 3.5 MeV are emitted “back-to-back”

Experiments on Experiments on developing neutron developing neutron

tagging method tagging method

D+T – n+D+T – n+

It is a challenge to discriminateIt is a challenge to discriminate

D+D – n+He-3D+D – n+He-3

D+D –t+pD+D –t+p

Experiments on tagging in collaboration with Italian Researchers

Simulated experiment on illicit material detection using tagged Simulated experiment on illicit material detection using tagged neutron techniqueneutron technique

Fig. 4 Gamma spectrum and time domain counting for tagged neutron analysis

DetectorsDetectors

We are conducting We are conducting experiments with NaI (3”, 5”). experiments with NaI (3”, 5”). BGO, LaBr to optimize the BGO, LaBr to optimize the detector configuration for a detector configuration for a workable detection system for workable detection system for cargo, vehicle.cargo, vehicle.

We are also developing We are also developing suitable electronics and data suitable electronics and data acquisition system for this acquisition system for this work. work.

Development of simulation tools

Simulation ModelSimulation Model

VARYING DENSITY OF ORGANIC / METALLIC MATRIXCargo 250 (W), 250 (H), 100 (L)

50 X 50 X50 cm3

TOP DETECTOR RESPONSE AS A TOP DETECTOR RESPONSE AS A FUNCTION OF TIMEFUNCTION OF TIME

Tagging Interval

signal to noise ratio increases in 30-50ns time interval indicating presence of an anomaly

FRONT DETCTOR FRONT DETCTOR RESPONSE AS A RESPONSE AS A

FUNCTION OF TIMEFUNCTION OF TIME

Tagging interval

Case study Case study

Varying explosive quantityVarying explosive quantityVarying explosive locationVarying explosive locationVarying density of embedded Varying density of embedded

matrixmatrixDifferent types of material such Different types of material such

as Nylon, Cocaine etcas Nylon, Cocaine etc

200kg explosive in 200kg explosive in 0.2gm/cc0.2gm/cc

N14 C12N14

O16

sum of counts of all top detector

in 27-45ns

Front DetectorFront Detector

C12

O16

50kg explosive in 50kg explosive in 0.2gm/cc0.2gm/cc

25kg explosive in 25kg explosive in 0.2gm/cc matrix0.2gm/cc matrix

200kg in 0.5gm/cc 200kg in 0.5gm/cc matrixmatrix

50Kg in 0.5gm/cc 50Kg in 0.5gm/cc matrixmatrix

25 kg explosive in 25 kg explosive in 0.5gm/cc matrix located 0.5gm/cc matrix located

near to top detectorsnear to top detectors

Location of detectors with Location of detectors with respect to explosive plays a respect to explosive plays a important role.important role.

Double sided scanning may Double sided scanning may help to improve the possibility help to improve the possibility of detection of explosivesof detection of explosives

Cocaine in a organic Cocaine in a organic matrix of 0.5gm/cc matrix of 0.5gm/cc

Organic matrix has self Organic matrix has self background which may be background which may be sufficient to shield these sufficient to shield these materials if put in high density materials if put in high density matrixmatrix

Need additional tool or Need additional tool or information to distinguish these information to distinguish these from organic materialsfrom organic materials

Detection of explosive with Detection of explosive with Tagged Neutron method will be Tagged Neutron method will be dependent of several factorsdependent of several factors

Quantity of explosiveQuantity of explosiveMatrix densityMatrix densityType of matrixType of matrixLocation of explosive in the cargoLocation of explosive in the cargoNature of surrounding matrixNature of surrounding matrixNature of background etcNature of background etc

Study of neutron Study of neutron backscattering method backscattering method for landmine detectionfor landmine detection

What are its potentials and limitations What kind of system will work in specific condition

Such studies have been carried out by other researchers for specific experimental systemand different source and experimental condition

Simulation geometrySimulation geometry

TNT

(C7H5N3O6

)

Neutron detector+ shielding

(2.5x2.5x15 cm3)

Soil

Mine depth (5cm -20cm)

DD/DT neutron source

Standoff distance (2cm)

PMA2-mine at the PMA2-mine at the depth 5cmdepth 5cm

Simulation for SNMSimulation for SNM

Schematic of SNM monitoring device

Plot of reaction rates as a function of Time with and without fissile material (A drum containing 0.5% of fissile material in 13.3 kg of actinide content)

Polythene

graphite

Multivariate calibrationMultivariate calibration

• • Often want to estimate a property based on a multivariate Often want to estimate a property based on a multivariate responseresponse

• • Typical casesTypical cases

• • Estimate analytic concentrations (Estimate analytic concentrations (yy) from spectra () from spectra (XX))

• • Finding Elemental composition (Finding Elemental composition (yy) from fluorescence ) from fluorescence spectrum (spectrum (XX))

• • Want solution of form Want solution of form Xb Xb = = y y + + ee

• • Problem: how to estimate Problem: how to estimate bb??

Further data analysis consists in decomposition of energy spectra of γ-rays collected for every “voxel” of the inspected volume, into contributions from various chemical elements.

Response function of individual elements

Partial least Square Partial least Square regressionregression

X is a matrix containing spectrum of several X is a matrix containing spectrum of several samples with known compositions samples with known compositions

Y is the matrix of concentrations of various Y is the matrix of concentrations of various elements present in the modeled samples then elements present in the modeled samples then their relation can be written their relation can be written

Let Y = XB + F (Where F is the matrix of Let Y = XB + F (Where F is the matrix of residual) (1)residual) (1)

The PLSR model can be considered as consisting The PLSR model can be considered as consisting of three relationsof three relations

X = TP’ + E, Y = UQ’ + F, and U = BTX = TP’ + E, Y = UQ’ + F, and U = BT Where P,Q are loading matrixes of X,Y. T,U are Where P,Q are loading matrixes of X,Y. T,U are

score matrix of X,Y and E,F are matrix of score matrix of X,Y and E,F are matrix of residuals. B is matrix relating X block scores to Y residuals. B is matrix relating X block scores to Y block scores. When all the scores are calculated block scores. When all the scores are calculated the concentration of unknown sample can be the concentration of unknown sample can be obtained from the following relation obtained from the following relation

Y = BTQ’ + FY = BTQ’ + F

PLS is related to PCR ( Principle component Regresion) and MLR (Multi Linear Regression)PCR captures maximum variance in XMLR achieves maximum correlation between X and YPLS tries to do both by maximizing covariance between X and Y

Calibration and cross-Calibration and cross-validationvalidation

Sample Sample ( wt % )H( wt % )H ( wt % ) C( wt % ) C ( wt % ) N( wt % ) N ( wt % ) O( wt % ) O

S1S1 55 2525 3030 4040

S2S2 66 1818 3535 4141

S3S3 55 2020 2828 4747

S4S4 88 2828 2020 4444

S5S5 22 3030 1818 5050

S6S6 33 2525 2222 5050

S7S7 44 1818 2525 5353

S8S8 66 2121 3030 4343

S9S9 44 1515 24 24 5757

S10S10 33 2323 3333 4141

Application of PLS technique in Application of PLS technique in quantitative determination of explosive quantitative determination of explosive

elementselements

S7S7 S8S8 S9S9 S10S10

HH ActualActual 44 66 44 33

PredictedPredicted 3.993.99 5.9925.992 4.474.47 2.612.61

CC ActualActual 1818 2121 1515 2323

PredictedPredicted 17.4917.49 20.9020.90 14.2814.28 23.0823.08

NN ActualActual 2525 3030 2424 2323

PredictedPredicted 25.7525.75 30.1630.16 25.0925.09 32.5032.50

OO ActualActual 5353 4343 5757 4141

PredictedPredicted 52.5352.53 43.4643.46 55.9955.99 41.5141.51

Artificial Neural Artificial Neural NetworkNetwork

(ANN) for Explosive (ANN) for Explosive DetectionDetection

Neural network Neural network architecturearchitecture

Neuron Model

Transfer functions

ANN model for ANN model for explosive detectionexplosive detection

Feed-forward network with backpropagation Feed-forward network with backpropagation algorithmalgorithm

Two stage networkTwo stage network 10 element vector input (C, H, N, O, Cl, C/N, 10 element vector input (C, H, N, O, Cl, C/N,

C/O, N/O, Cl/C, Cl/H)C/O, N/O, Cl/C, Cl/H) 29 patterns (explosives/narcotics)29 patterns (explosives/narcotics) 35 neurons in the hidden layer35 neurons in the hidden layer

Tan-sigmoid transfer function

Tan-sigmoid transfer function

Feed-Forward Network

Training dataTraining data

Input Input Vector Vector ElementElement

ParametParameterer

11 CC

22 HH

33 NN

44 OO

55 ClCl

66 C/OC/O

77 C/NC/N

88 N/ON/O

99 Cl/CCl/C

1010 Cl/HCl/H

Training PerformanceTraining Performance

Recall test valuesRecall test values

Input: Original input values used in training

Simulated Input for:

RDX: [16.22 2.72 37.84 43.22 0 0.42865 0.87552 0.37529 0 0 ]

Cocaine: [67.3 6.9 4.6 21.1 0 14.63 0.2 3.2 0 0 ]

Recall test values with Recall test values with 5% error5% error

Input: 5% random error added to original input values used in training

Simulated Input for:RDX: [15.855 2.6772 37.75 44.995 0 0.44322 0.91611 0.37401 0 0 ]

Cocaine: [70.514 6.8679 4.5525 21.77 0 15.223 0.19993 3.12 0 0 ]

LimitationsLimitations

The method is slower The method is slower compared to X-ray (seconds vs compared to X-ray (seconds vs minutes)minutes)

Can be used as confirmatory Can be used as confirmatory sensorsensor

Still much work remains to be Still much work remains to be done to make it commercial done to make it commercial

ConclusionsConclusions

We have reviewed various methods We have reviewed various methods of explosive detectionof explosive detection

The necessary steps in developing The necessary steps in developing such systems have been highlightedsuch systems have been highlighted

We have described our work at We have described our work at BARC for this developmentBARC for this development

We have brought out We have brought out multidisciplinary nature of this workmultidisciplinary nature of this work

We have also pointed out the We have also pointed out the limitations of the techniquelimitations of the technique