Time-Dependent Delayed Signatures From Energetic Photon Interrogations
A pulsed photonuclear interrogation environment is rich with time-dependent, material specific, radiation signatures. Exploitation of these signatures in the delayed time regime (>1us after the photon flash) has been explored through various detection schemes to identify both shielded nuclear material and nitrogen-based explosives. Prompt emission may also be invaluable for these detection methods. Numerical and experimental results, which utilize specially modified neutron and HpGe detectors, are presented which illustrate the efficacy of utilizing these time-dependent signatures. Optimal selection of the appropriate delayed time window is essential to these pulsed inspection systems. For explosive (ANFO surrogate) detection, both numerical models and experimental results illustrate that nearly all 14N(n,y) reactions have occurred within l00 us after the flash. In contrast, however, gamma-ray and neutron signals for nuclear material detection require a delay of several milliseconds after the photon pulse. In this case, any data collected too close to the photon flash results in a spectrum dominated by high energy signals which make it difficult to discern signatures from nuclear material. Specifically, two short-lived, high-energy fission fragments (97Ag(T1/2=5.1 s) and 94Sr(T1/2=75.2 s)) were measured and identified as indicators of the presence of fissionable material. These developments demonstrate that a photon inspection environment can be exploited for time-dependent, material specific signatures through the proper operation of specially modified detectors.
- Research Organization:
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- DOE - NE
- DOE Contract Number:
- DE-AC07-99ID-13727
- OSTI ID:
- 915514
- Report Number(s):
- INL/CON-06-11169; TRN: US0804996
- Resource Relation:
- Conference: Conference on Accelerator Applications in Research and Industry,Fort Worth, Texas,08/21/2006,08/25/2006
- Country of Publication:
- United States
- Language:
- English
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