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Using Nuclear Resonance Fluorescence to Isotopically Map Containers

Using Nuclear Resonance Fluorescence to Isotopically Map Containers. Micah S Johnson, D.P. McNabb. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Outline. Motivation for isotopic mapping

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Using Nuclear Resonance Fluorescence to Isotopically Map Containers

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  1. Using Nuclear Resonance Fluorescence to Isotopically Map Containers Micah S Johnson, D.P. McNabb This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  2. Outline • Motivation for isotopic mapping • Nuclear Resonance Fluorescence • NRF scanning technologies • FINDER - transmission detection • Feasibility test at Duke • NRF measurements on Pu • Future NRF measurements

  3. Current systems: radiography

  4. Limitation: density silhouette

  5. NRF  isotopic sensitivity

  6. Programmatic Needs • Applications of NRF detection technology • Contraband detection • Safeguards • Fuel assay • Waste assay • Examples of some materials that may be of interest • 239Pu, 235U, 233U, 237Np • NRF scanning technologies will detect: • Presence of materials • Amount of material

  7. AZ AZ Nuclear Resonance Fluorescence (NRF) • An energetic photon (-ray) at a resonant energy of a particular isotope can excite that isotope. • The excited nucleus then will decay by emitting a set of -rays • Dipole excitations (e.g. scissors mode) Level sensitive to -ray excitations -ray or

  8. Proposed NRF scanning methods • Reflective • Detectors are arranged at back-angles relative to the -ray source and facing the container • Directly detect NRF scatter from within the container • Positive result occurs when the detected NRF photon is identified with a material of interest • Transmissive • Witness foil is placed on the opposite side of the container relative to the -ray source • Detectors are at back-angles focused on the foil • Positive result occurs when no NRF scatter is detected from foil Each has its own advantages and disadvantages

  9. Schematics of proposed NRF scan techniques Container Reflection: Transmission: Detectors -ray source Witness Foil Transmission: scatter occurs in container OR from witness foil

  10. Transmission technique Container Witness Foil -ray source If material is present then the incident spectrum obtains a notch

  11. Transmission technique Container Pass: Fail: Witness Foil -ray source Scatter from witness foil exposes NRF lines OR not

  12. LLNL concept: FINDER FINDER has quantifiably low false positive and false negative rates -- concept details are published: Pruet et al., J. Appl. Phys. 99, 123102 (2006).

  13. FINDER Demo: setup at HIgS Recent feasibility test at Duke University’s FEL with HIgS Detectors Cargo: W and/or DU Witness Foil: DU HIgS -ray source Flux Monitor NRF scatter for DU occurs in cargo area OR from witness foil

  14. HIgS

  15. FINDER Demo: cargo area Cargo

  16. FINDER Demo: witness foil

  17. FINDER Demo: flux monitor

  18. FINDER Demo: HIgS results Gated spectra:

  19. FINDER Demo: HIgS results (continued) • Different cargo configurations listed on left. Raw counts and counts normalized to fluence in the dominant peak at 2176 keV are shown. • Results are consistent with no notch refilling • More statistics are needed.

  20. Pu measurements at HVRL at MIT The FINDER/NRF technique seems to work (with additional study required). Therefore, we need to identify NRF states in different materials, e.g. Pu, U, etc… *This effort can be done in parallel to fine-tuning of FINDER.

  21. Pu target: Pu Mass: 3.8-grams Diameter: 1.4-cm Thickness: 1.5-mm Nitronic-40 holder: 25-g (63%Fe, 21%Cr, 6%Ni, 9%Mn) We used 2 of these lollipops for 7.5 g of Pu

  22. Experimental Setup: (Passport) Radiator: 102-m Au on 1-cm Cu (cooling and e- cleanup) e-beam

  23. Experimental End Station Collimator/Radiator NRF target HPGe X-ray Imager

  24. Previous NRF measurements NRF measurement on Pu at MIT with bremsstrahlung source

  25. Ex E= Ex E= Ex-7.9 7.9-keV 0.0 GS NRF results for 239Pu Transition Energy Sigma Cross-section (eV barns) Systematics imply these resonances are magnetic dipole

  26. Higher lying resonances? • Systematics of actinides and rare-earths indicate that magnetic dipole strength is closer to 3 MeV • Sensitivity region for HVRL measurement is less than 2.5 MeV • Will perform NRF measurements at UCSB • Electron accelerator maximum ~ 6 MeV • For average strengths: • Sensitivity range is 500 keV below endpoint • Sensitivity range is 500 keV wide

  27. Status of UCSB work • Passport has completed upgrade to their end-station at UCSB that includes 7 HPGe detectors • Collaborating with UC Berkeley, Rick Norman. • Try to get 56Co source to measure absolute efficiency. • Subcontract with Passport Systems is in place • Pu target (3 grams) at UCSB August Measurements

  28. HPGe Detectors X-ray Imager Photon Beam NRF Target Bremsstrahlung Source UCSB setup

  29. Future work • Future measurements at HIgS: • Pu and U isotopes • 237Np and 241Am • Will be able to extract M1 versus E1 • Pending funds from DOE

  30. Summary • NRF measurements have been performed on 239Pu and 13 new (~dipole) levels have been discovered in 239Pu < 2.5 MeV • Measurements on 239Pu will be performed in August at UCSB to search for resonances > 2.5 MeV • Feasibility test of the NRF technique to scan containers has been performed at Duke • Future measurements of NRF states will be performed at Duke pending DOE funding

  31. Collaboration • M.S. Johnson, D.P. McNabb, C.A. Hagmann, E.B. Norman, LLNL • W. Bertozzi, S.E. Korbly, R.J. Ledoux, W.H. Park, Passport Systems Inc. • Facilities at UCSB and HVRL/MIT

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