Principles and Applications of Neutron Based Inspection Techniques. Tsahi Gozani Rapiscan Laboratories 520Almanor Ave, Sunnyvale, CA

Transcription

1 Principles and Applications of Neutron Based Inspection Techniques Tsahi Gozani Rapiscan Laboratories 520Almanor Ave, Sunnyvale, CA Presentation to the International Topical meeting on Nuclear Research Applications and Utilization of Accelerators May 4 th -8 th,2009, IAEA, Vienna, Austria

2 Elemental composition of typical threats & benign materials Threat/Material determination Elemental composition γ spectral signatures Threat C H N O P F Cl S N/H N/C Explosives C TNT PETN AN Chem. agents Sarin VX CA (H-Cyanide) HD (Mustrad gas) Phosgene Benign Water Paper Plastic Salt 60 0

3 Total cross sections of organic elements-determining penetrability but also provide signatures (e.g. resonance structure) Total neutron cross section (barn) O H C HO C N O Neutron H

4 Neutron inelastic scattering cross sections. Reaction provides unique γ signatures Neutron inelastic cross section (barn) N N C O H (σ tot ), for reference Neutron

5 Fission cross sections-cover more than 2 orders of magnitude Affording thermal, epi-thermal and fast fission Fission cross section (barns) U235H Pu239 Np237 U238 Th232 Neutron

6 Penetrability of source neutrons Neutron flux (fission rate) vs. water density for different neutron source energies Fission Rate (Isotropic & collimated ources) Fission Rate (1/cm^3) 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 1.E-09 Matrix Density (g/cm^3) MeV 0.06 MeV, iso 14 MeV Cf Matrix Thickness (g/cm^2) 14 MeV,iso Cf-iso Source Isotropic Collimated Water at different densities Neutron attenuation in water (and other hydrogenous substances). The lower the source energy the higher the attenuation. The flux is lower by several order of magnitude between lower (<100KeV) and higher (>2MeV) neutron energies.

7 Explosive signature provided by VEDS (TNA component) 1.E+08 1.E+07 B10 capture Counts (0.05 MeV^-1 * 300 sec^-1) 1.E+06 1.E+05 1.E+04 1.E+03 H capture Fe capture Cou nts (0. 05 MeV^- 1 * 300 sec^ -1) AN at Center 800 AN Close to U2 AN Close to U1 700 Empt y E+02 N capture 1.E

8 Signatures: VEDS (TNA) Time Dependent Spectra- Early Thermal n-capture Time Domain detector counts Thermal Gamma-ray Spectrum Comparison from LDVEDS detector Acquisition start ~50 microseconds after neutron H 2.22 pulse and ends 1 ms after neutron pulse Fe 7.64 Fe 9.3 N 10.8 Clothing/Shoes Cargo Steel Cargo Wood Cargo E (MeV)

9 Signatures: VEDS (TNA) Time Dependent Spectra- Late Thermal n- Capture Time Domain Activation Gamma-ray Spectrum Comparison from LDVEDS detector Acquisition start 4.3 ms after neutron pulse and ends about 7.3 ms after pulse detector counts Iodine 2.13 MeV beta 25 m half-life Oxygen 6.13 Fe 7.64 Clothing/Shoes Cargo Steel Cargo Wood Cargo E (MeV)

10 Signatures: VEDS (TNA) Time Dependent Spectra- Activation (long term) Time Domain 1E+06 Short tern (5-10s) delayed activation following14mev neutron irradiation of cargo of clothing and shoes 1E+05 counts 1E+04 1E+03 1E I 2.13 MeV beta-decay 25 m half-life (inside NaI O 6.13 O 6.9, 7.1 1E E (MeV)

11 Inelastic scattering & signatures

12 PFNA Material Signatures-TOF NaI spectra from (n, n γ) reaction Rice Cocaine C4 Explosive Glass Aluminum Oxygen Acetone Apples Sarin Leather Silicon Nitrogen Polyethylene Coffee Water Plastic Iron Carbon

13 A concept of operation of NII: Neutron based technique clears alarms of high throughput primary inspection X-ray inspection X-ray image w/suspected anomalies Anomalies cleared or validated by active neutron based NII

14 14MeV neutron based Vehicle Explosive Detection System (VEDS)

15 Differential Die Away Analysis for SNM Detection in Cargo Differential Die Away Analysis for SNM Detection Count per source neutron monitor Detector signal with SNM sample at various locations in paper cargo) Background ( detector signal with no SNM in paper cargo) Cosmic rays background Time from the initial pulse trigger (ms)

16 Neutron Inspection Products Rapiscan VEDS Mobile Vehicle Explosive Detection System Rapiscan VEDS Gantry Vehicle Explosive Detection System Rapiscan PFNA Air Cargo Inspection System

17 Summary of techniques, principles & major elements detected # Technique Name 1 TNA (Thremal neutron analysis) 2 FNA (Fast neutron analysis) Probing Radiation Main Nuclear Reaction Detected Radiation Thermalized neutrons (n,γ) Neutron capture γ- rays/prompt & delayed neutrons and γ rays for SNM 2 (n,n γ) Fast (high energy, usually 14 MeV) neutrons 3 FNA/TNA Pulsed neutron source; fast neutrons during the pulse, thermal neutrons between pulses 4 PFNA (ns Pulsed fast neutron analysis) 5 API (Associated particles inspection) 6 NRA (Neutron resonance absorption) Nanosecond (ns) pulses of fast neutrons 14 MeV neutrons in coincidence with the associated -particles Nanoseconds pulsed fast neutrons (0.5-4 MeV), broad energy spectrum (n,n γ) + (n,γ) γ-rays produced from inelastically scattered neutrons During pulse (FNA), after pulse (TNA) (n,n γ) Like FNA w/tof 3 /prompt & delayed neutrons and γ rays for SNM (n,n γ) Like FNA in delayed coincidence with (n,n) Elastically and resonantly scattered neutrons Sources 252 Cf, also accelerator based sources (ENG 1 ) ENG based on (d,t) μs pulsed ENG based on (d,t) Primary & Secondary Detected Elements Cl, N, SNM** H, Metals, P, S O, C (N) (H) Cl, P N, Cl, SNM H, C, O, P, S ns pulsed (d,d) O, C, N, Cl, accelerator with E d Others, SNM ~6 MeV H, Metals, Si, P, S, Others (d,t) O, C, N Accelerator based ns pulsed (d,be) or (d,d) w/angular correlation, with E d 4 MeV Metals H, O, C, N (Others)

18 END