Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory Current systems: radiography

4 Lawrence Livermore National Laboratory Limitation: density silhouette

5 Lawrence Livermore National Laboratory NRF  isotopic sensitivity

6 Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory 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) AZAZ  -ray Level sensitive to  -ray excitations AZAZ or

8 Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory Schematics of proposed NRF scan techniques  -ray source Detectors Witness Foil Transmission: scatter occurs in container OR from witness foil Reflection: Transmission: Container

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

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

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

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

14 Lawrence Livermore National Laboratory HIgS

15 Lawrence Livermore National Laboratory FINDER Demo: cargo area Cargo

16 Lawrence Livermore National Laboratory FINDER Demo: witness foil

17 Lawrence Livermore National Laboratory FINDER Demo: flux monitor

18 Lawrence Livermore National Laboratory FINDER Demo: HIgS results Gated spectra:

19 Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory 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) Pu target: We used 2 of these lollipops for 7.5 g of Pu

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

23 Lawrence Livermore National Laboratory Experimental End Station HPGe NRF target Collimator/Radiator X-ray Imager

24 Lawrence Livermore National Laboratory Previous NRF measurements NRF measurement on Pu at MIT with bremsstrahlung source

25 Lawrence Livermore National Laboratory NRF results for 239 Pu Systematics imply these resonances are magnetic dipole 7.9-keV 0.0 GS ExEx E=ExE=Ex E  = E x -7.9 Transition EnergySigmaCross-section (eV barns)

26 Lawrence Livermore National Laboratory 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 Lawrence Livermore National Laboratory 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 56 Co source to measure absolute efficiency.  Subcontract with Passport Systems is in place  Pu target (3 grams) at UCSB August Measurements

28 Lawrence Livermore National Laboratory UCSB setup NRF Target Bremsstrahlung Source X-ray Imager HPGe Detectors Photon Beam

29 Lawrence Livermore National Laboratory Future work  Future measurements at HIgS: Pu and U isotopes 237 Np and 241 Am  Will be able to extract M1 versus E1  Pending funds from DOE

30 Lawrence Livermore National Laboratory Summary  NRF measurements have been performed on 239 Pu and 13 new (~dipole) levels have been discovered in 239 Pu < 2.5 MeV  Measurements on 239 Pu 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 Lawrence Livermore National Laboratory 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