Warhead verification as inverse problem: Applications of neutron spectrum unfolding from organic-scintillator measurements

Chris C. Lawrence, Michael Febbraro, Marek Flaska, Sara A. Pozzi, F. D. Becchetti

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Verification of future warhead-dismantlement treaties will require detection of certain warhead attributes without the disclosure of sensitive design information, and this presents an unusual measurement challenge. Neutron spectroscopy - commonly eschewed as an ill-posed inverse problem - may hold special advantages for warhead verification by virtue of its insensitivity to certain neutron-source parameters like plutonium isotopics. In this article, we investigate the usefulness of unfolded neutron spectra obtained from organic-scintillator data for verifying a particular treaty-relevant warhead attribute: the presence of high-explosive and neutron-reflecting materials. Toward this end, several improvements on current unfolding capabilities are demonstrated: deuterated detectors are shown to have superior response-matrix condition to that of standard hydrogen-base scintintillators; a novel data-discretization scheme is proposed which removes important detector nonlinearities; and a technique is described for re-parameterizing the unfolding problem in order to constrain the parameter space of solutions sought, sidestepping the inverse problem altogether. These improvements are demonstrated with trial measurements and verified using accelerator-based time-of-flight calculation of reference spectra. Then, a demonstration is presented in which the elemental compositions of low-Z neutron-attenuating materials are estimated to within 10%. These techniques could have direct application in verifying the presence of high-explosive materials in a neutron-emitting test item, as well as other for treaty verification challenges.

Original languageEnglish (US)
Article number064501
JournalJournal of Applied Physics
Volume120
Issue number6
DOIs
StatePublished - Aug 14 2016

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

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