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Title: A Hierarchical Bayesian Approach to Neutron Spectrum Unfolding With Organic Scintillators

Journal Article · · IEEE Transactions on Nuclear Science

We propose a hierarchical Bayesian model and a state-of-the-art Monte Carlo sampling method to solve the unfolding problem, i.e., to estimate the spectrum of an unknown neutron source from the data detected by an organic scintillator. Inferring neutron spectra is important for several applications, including nonproliferation and nuclear security, as it allows the discrimination of fission sources in special nuclear material (SNM) from other types of neutron sources based on the differences of the emitted neutron spectra. Organic scintillators interact with neutrons mostly via elastic scattering on hydrogen nuclei and therefore partially retain neutron energy information. Consequently, the neutron spectrum can be derived through deconvolution of the measured light-output spectrum and the response functions of the scintillator to monoenergetic neutrons. The proposed approach is compared to three existing methods using the simulated data to enable controlled benchmarks. We consider three sets of detector responses. One set corresponds to a 2.5-MeV monoenergetic neutron source and two sets are associated with (energywise) continuous neutron sources (252Cf and 241AmBe). Our results show that the proposed method has similar or better unfolding performance compared with other iterative or Tikhonov regularization-based approaches in terms of accuracy and robustness against limited detection events while requiring less user supervision. The proposed method also provides a posteriori confidence measures, which offers additional information regarding the uncertainty of the measurements and the extracted information.

Research Organization:
Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
NA0002534; 31310019M0011
OSTI ID:
1812845
Alternate ID(s):
OSTI ID: 1798669; OSTI ID: 1861153
Journal Information:
IEEE Transactions on Nuclear Science, Journal Name: IEEE Transactions on Nuclear Science Vol. 66 Journal Issue: 10; ISSN 0018-9499
Publisher:
Institute of Electrical and Electronics EngineersCopyright Statement
Country of Publication:
United States
Language:
English