simulation of tagged neutron imaging technique

Amar Sinha, Y. Kashyap, Tushar Roy, P.S. Sarkar, Mayank Shukla

Laser and Neutron Physics section,

Bhabha Atomic Research Centre,Trombay, Mumbai -400 085

SIMULATION OF TAGGED SIMULATION OF TAGGED

NEUTRON IMAGING TECHNIQUENEUTRON IMAGING TECHNIQUE

About Our workAbout Our work

�� Imaging neutron and XImaging neutron and X--rayray

�� Imaging with low intensity neutron Imaging with low intensity neutron

sourcessources

�� Design of neutron sources Design of neutron sources ––

photoneutronphotoneutron source source --MicrotronMicrotron

�� Simulation studies for design of source Simulation studies for design of source

and its application and its application ––radiography, radiography,

tomographytomography

�� XX--ray ray –– 3D tomography, phase imaging 3D tomography, phase imaging

etcetc

�� Real time applications to high speed Real time applications to high speed

phenomenonphenomenon

Test tube

With water Zircloy piece loaded

With hydrogen

Plastic screw

14 MeV Generator

108n/s

n-scintillation

We have used Pu-Be source for

imaging – can be used for imaging at inaccesible places

Also used 108 n/s 14 MeV neutron generator

This generator is under renovation and

you may get opportunity to see this

APPLICATION DEVELOPMENTAPPLICATION DEVELOPMENT

�� 2D & 3D NEUTRON TOMOGRAPHY 2D & 3D NEUTRON TOMOGRAPHY

(USING REACTOR(USING REACTOR))

0 Volume rendered image obtained using Fig. 11 Cut away view to show broken

the broken rod.

a b

MICROTRON BASED NEUTRON SOURCEMICROTRON BASED NEUTRON SOURCE

BeTantalum

electron-photon- neutron

e

nγγγγ

Why Be?

Are there other combinations-composite

Target?

THE DESIGN FROM BASICS?

high energy electrons to produce photons

- Photons then produce neutrons through photo-neutron reaction

-Advantages are that photon yields are very high and can make up

for lower cross-sections

Why Be?

Reason –Cross-section-If using low energy accelerator Be

is the only choice –Lower Cross-section is compensated by utilization of large softer spectrum between 1.66 and 3 MeV.

At Higher EnergiesBe cross-section lowerby several factors

For Higher Electron

Energy –use composite Target Be for lower part

Of spectrum and U for

Higher energy component

DESIGN OF MICROTRON BASED DESIGN OF MICROTRON BASED

NEUTRON SOURCE AND NEUTRON SOURCE AND

APPLICATIONSAPPLICATIONS

�� Electron beam Electron beam -- 99--12 MeV12 MeV

�� current current --30mA(peak), 1030mA(peak), 10µµµµµµµµA (avg..)A (avg..)

�� Pulse width Pulse width –– 2.7 2.7 µµµµµµµµss

�� Pulse repetition rate: 50Pulse repetition rate: 50--250 Hz(max)250 Hz(max)

�� Bremsstralung Target Bremsstralung Target --tantalumtantalum�� Expected photon yield at 9 MeV electron energy : Expected photon yield at 9 MeV electron energy :

6x106x101313 p/s and for 12 MeV : 9.7 x10p/s and for 12 MeV : 9.7 x101313p/s (Ep/s (Ephph>1.67 >1.67 MeV) MeV)

�� TargetTarget-- BeBe--Uranium compositeUranium composite

�� our design 4cm Be in front optimum+1cm Uour design 4cm Be in front optimum+1cm U

�� Present Present ––30 30 mAmA, 2 , 2 µµµµµµµµss ,50 Hz ,50 Hz –– 2x102x109 9

n/sn/s --6 6 µµµµµµµµAA

�� expected yield of neutron for 9 expected yield of neutron for 9 MeVMeVelectron with optimized target design electron with optimized target design : ~2x10: ~2x101010n/s ,For 12 n/s ,For 12 MeVMeV: ~4x10: ~4x101010n/sn/s

High Pressure Physics Division, BARCHigh Pressure Physics Division, BARC

E- 9 MeV; Rep rate: 50Hz ; Pulse width: 2µµµµs

Peak Current:30mA

Thickness of Be Experimental

n/Sec

Simulation

2cm 1.4361*109 1.34*109

4cm 2.2866*109 2.25*109

6cm 2.6024*109 2.91*109

8cm 3.0708*109 3.37*109

Polyethylene Be Uranium

Lead

Thermal Neutron Radiography

In collaboration with other institutionsWe are part of a team designing indigenous high energy cargo system – our responsibility in

this project is high energy x-ray imaging system

Is High Energy cargo XIs High Energy cargo X--ray inspection system ray inspection system

––also a neutron source???also a neutron source???

Can Electron accelerators used as photo neutron sourcesCan Electron accelerators used as photo neutron sources

be used for elemental characterization??be used for elemental characterization??

��There are serious obstacle to this approachThere are serious obstacle to this approach--

��What about the enormous high energy XWhat about the enormous high energy X--ray photons which ray photons which

are the source of neutrons itself are the source of neutrons itself --background???? background???? --Is there Is there

a solution to this?a solution to this?

��if it can be used it provides cheaper solution and can act if it can be used it provides cheaper solution and can act

as second check with no extra generatoras second check with no extra generator

This possibility –actually next part of CRP

What has been our What has been our

interest in this CRPinterest in this CRP

Aim has been evaluation of various methods for the detection of illicit materials in marine cargo, vehicles

In particular we are interested in exploring Associated Particle Imaging method , exploring use of PTFNA for vehicle borne explosives, Photo-neutron sources for cargo inspection

Our focus has been on simulation studies of such systems

We also plan to develop detection system for photo neutron sources.

AIM OF PRESENT CRPAIM OF PRESENT CRP

�� Simulation of tagged Neutron based Simulation of tagged Neutron based

techniques and elemental techniques and elemental

characterization for illicit materials and characterization for illicit materials and

explosivesexplosives

�� Development of reconstruction Development of reconstruction

algorithm for prompt gamma spectrum algorithm for prompt gamma spectrum

and their testing for 3D imaging of and their testing for 3D imaging of

explosives and illicit material and explosives and illicit material and

detection of fissionable material.detection of fissionable material.

�� Feasibility of explosive detection and Feasibility of explosive detection and

elemental characterization using elemental characterization using

photoneutronphotoneutron and/or isotope based and/or isotope based

sourcesource

Key signatures inelastic gamma C , O, N

For explosives and in case illicit Materials lines of Cl.

Neutron based explosive detection methodsdetect explosives by identifying their

elemental components.

Simulations : Neutron based techniques

What useful info can be What useful info can be

obtainedobtained

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

Basics of TaggingBasics of Tagging

Simulation to evaluate the technique

Simulation ModelSimulation Model

VARYING DENSITY OF ORGANIC / METALLIC MATRIX

Cargo 250 (W), 250 (H), 100 (L)

50 X 50 X50 cm3

Detector moduleDetector module

NaI detector 5 inch dia 10 inch length

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

TOP detector response TOP detector response

Increase signal

Count vs individual detector position

Front detector responseFront detector response

CONCLUSIONCONCLUSION

�� TOP detectors are more sensitive TOP detectors are more sensitive

to the presence of anomaly due to to the presence of anomaly due to

absence of less direct neutronsabsence of less direct neutrons

�� One can use more efficient TOP One can use more efficient TOP

detector array while simple detector array while simple NaINaI will will

suffice in front panel of detectors suffice in front panel of detectors

with reduced numberswith reduced numbers

�� If contribution of direct neutrons If contribution of direct neutrons

can be avoided front detectors may can be avoided front detectors may

be of great value. be of great value.

Case study Case study

�� Varying explosive quantityVarying explosive quantity

�� Varying explosive locationVarying explosive location

�� Varying density of embedded Varying density of embedded

matrixmatrix

�� Different 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


0.2gm/cc0.2gm/cc

N14 C12N14

O16

Front DetectorFront Detector

C12

O16

100kg of explosive in 100kg of explosive in

0.2gm/cc0.2gm/cc

12C 12O

Front detectorsFront detectors


0.2gm/cc0.2gm/cc

Front Front detctorsdetctors


0.2gm/cc matrix0.2gm/cc matrix

FRONT DETECTORSFRONT DETECTORS

CONCLUSIONSCONCLUSIONS

�� As the explosive quantity As the explosive quantity

decreases it becomes difficult decreases it becomes difficult

to detect the explosivesto detect the explosives

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

matrixmatrix

100Kg in 0.5gm/cc 100Kg in 0.5gm/cc

matrixmatrix


matrixmatrix

CONCLUSIONSCONCLUSIONS

�� For high density matrix the For high density matrix the

detection of small quantity of detection of small quantity of

explosive/illicit material using explosive/illicit material using

this technique is not possiblethis technique is not possible

�� This imposes a limit on This imposes a limit on

minimum detectable quantity of minimum detectable quantity of

such materials in a high such materials in a high

density matrixdensity matrix

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



away from top detectorsaway from top detectors

ConclusionConclusion

�� 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

100kg Nylon in metallic 100kg Nylon in metallic

matrix of 0.5gm/ccmatrix of 0.5gm/cc


�� Materials such as nylon can be Materials such as nylon can be

easily distinguished by weak easily distinguished by weak

presence of Opresence of O1616 signature signature

�� However as stated earlier However as stated earlier

organic cargo scanning need organic cargo scanning need

special treatment to improve special treatment to improve

signal to noise ratiosignal to noise ratio

Overall CONCLUSIONOverall CONCLUSION

�� 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 explosive

�� Matrix densityMatrix density

�� Type of matrixType of matrix

�� Location of explosive in the cargoLocation of explosive in the cargo

�� Nature of surrounding matrixNature of surrounding matrix

�� Nature of background etcNature of background etc

Next 18 months planNext 18 months plan

Continuation of these simulation studies of tagged Continuation of these simulation studies of tagged

neutron system to know its limitations and potentials neutron system to know its limitations and potentials

--also for vehicle borne system and smaller luggage. also for vehicle borne system and smaller luggage.

�� Simulation of PTFNA method for medium sized Simulation of PTFNA method for medium sized

system such as vehicle borne explosive systemsystem such as vehicle borne explosive system

Analysis of various scenarios such asdifferent explosive quantities within organic

Medium of various densities

-Simulation for testing suitability of Tagged neutron method for smaller objects

Fast Neutrons

Thermal Neutrons

10 µs 90 µs

Reactions

Gamma

Elements

(n,n’γ), (n,pγ)

Prompt

C, O

(n,γ)

Prompt

H, S, Cl, Fe, N ...

Activation

(n,α), (n,p)

Delayed

O, Al, Si

Feasibility study of using high energy XFeasibility study of using high energy X--ray ray

system for simultaneous neutron inspectionsystem for simultaneous neutron inspection

�� As it was discussed earlier, there are major problem As it was discussed earlier, there are major problem such as high primary gamma. However many of the such as high primary gamma. However many of the electron electron LinacLinac that are being used for cargo scanning that are being used for cargo scanning are high rep rate pulsed system (a few microare high rep rate pulsed system (a few micro--sec sec

pulsed) pulsed)

�� One of the solutions to the problem of detecting neutron One of the solutions to the problem of detecting neutron induced gamma in presence of primary gamma could induced gamma in presence of primary gamma could bebe to gate the detector system such that first to gate the detector system such that first few microfew micro--sec the detector system is shutoff.sec the detector system is shutoff.

�� Such a concept will be tested by simulationSuch a concept will be tested by simulation

�� This will be followed by testing this concept on This will be followed by testing this concept on microtronmicrotron based neutron system which also based neutron system which also has similar characteristics. has similar characteristics.

Fast Neutrons

Thermal Neutrons

10 µs 90 µs

Reactions

Gamma

Elements

(n,n’γ), (n,pγ)

Prompt

C, O

(n,γ)

Prompt

H, S, Cl, Fe, N ...

Activation

(n,α), (n,p)

Delayed

O, Al, Si

Decision algorithm Decision algorithm

DevelopmentDevelopment

�� As pointed out by Prof As pointed out by Prof

KuznetsovKuznetsov and Prof and Prof LanzaLanza, the , the

decision making algorithm decision making algorithm

plays important role.plays important role.

�� We plan to address this We plan to address this

problem in next part of CRP.problem in next part of CRP.

simulation of tagged neutron imaging technique

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