1. Monte Carlo simulation of active neutron interrogation system developed for detection of illicit materials
А.Sh. Georgadze
Kiev Institute for Nuclear Research
2nd Jagelonian Symposium on Fundamental and Applied Subatomic Physics

2. Associated alpha-particle detection
Probing with fast-neutron analysis (FNA) can excite gamma rays from carbon and oxygen found in excess in these explosives. To enhance the signal from the target and suppress background noise used a generator that produces back-to-back neutrons and α particles (a technique called associated-particle imaging) to identify the volume in which the neutron produces a gamma ray by tagging its time of emission and direction 

3. Explosive detection
Using gamma lines after Nitrogen and Oxygen nuclei excitation
Detect automatically 30 explosives
High cost EURO !

4. Experiment in Ukraine Neutron generator ІNG-3
matrix 11×13 CsI (30×30 cm) with coded aperture mask
Need repeat 5 times with changed mask.
150 см
TNT

5. Chemical composition of explosives, drugs and common materials

6. Compact neutron generators
Neutron flux 108 – 1014 n/s

7. Neutron pulses /s

8. Cost effective gamma/neutron detector design
Have applied block-detectors design (for PET) → less number of PMTs
Photomultipliers
PMT 9 х 9
Light sharing light guide
Scintillation bars
30 bars 50 mm х 50 mm x 400 mm - plastic scintillator
10 bars 50 mm х 50 mm x 400 mm
- CsI scintillator
plastic scintillator - scatterer
CsI (BGO) - absorber

9. Neutron captur gated detection principle
Fast signal from proton γ n Gd p
  8 MeV n
t 25 ms
Delayed signal

10. Scintillation bar enclosing
Neutron
captured
by Gd [%]
mean time until
the capture [μs]
5  5 cm 88 25
55400 сm3
Plastic scintillator
Mylar
Gadolinium oxide containing film
Light output ph/МеV

11. Compton imaging of gamma sources

12. GEANT4 simulation of Compton scattering
Gamma-ray source
Gray rays - gammas Green rays – electrons

13. Electronic collimation simulation
Gamma ray beam direction

16. Electronic collimation

17. GEANT4 simulation of fissile material detection with neutron analysis
Neutron generator
Gamma/neutron detector
Fissile or explosive
material
Distance to gamma/neutron detector 40 cm

18. Chemical compositions of the materials used for the simulation
Explosives
Composition
1. Ammonium nitrate
H4N2O3
2. Ammonium picrate
C8H8N4O7
3. RDX
C3H8N8O8
4. Ethylenediamine
C2H10N4O6
5. TNT
C7H6N703
6. C4
C4H6N6O6
7. CL20
C8H8N12O12
8. Nitrocellulose
C8H7N3O11
9. Nitroglycerine
C3H8N3O3

19. Simulation of detected gamma-quanta and neutrons hitting detector -
neutron generator flux n/s expositions 1 min
Material
number of
neutrons
gammas
PLUTONIUM_DIOXIDE+
4,80E+03
5,52E+04
URANIUM_OXIDE
4,20E+03
4,96E+04
G4_CELLULOSE NITRATE
2,51E+03
2,45E+04
G4_NYLON-11_RILSAN
2,40E+03
2,36E+04 AN
2,96E+04
4,12E+04
TNT
2,66E+04
RDX
3,00E+03
5,46E+04
CL20
2,80E+03
5,91E+04
No object
2,10E+03
2,06E+04

20. GEANT4 simulation of explosive detection with neutron analysis
Blue rays – neutrons
Red rays - gammas
Neutron generator
Gamma/neutron detector
Explosive
SiO2