scholarly journals Uranium Fission Fragment Properties Across a Broad Incident Neutron Energy Spectrum

2015 ◽  
Author(s):  
Dana Lynn Duke
Keyword(s):  
Energy Spectrum ◽  
Neutron Energy ◽  
Fission Fragment ◽  
Neutron Energy Spectrum ◽  
Incident Neutron ◽  
Incident Neutron Energy ◽  
Uranium Fission

Space to Air High-Altitude Region Adjoint Neutron Transport

2021 ◽  
pp. 154851292110316
Author(s):  
Zachary W LaMere ◽  
Darren E Holland ◽  
Whitman T Dailey ◽  
John W McClory
Keyword(s):  
Energy Spectrum ◽  
High Altitude ◽  
Neutron Energy ◽  
Neutron Transport ◽  
Energy Sources ◽  
Source Spectrum ◽  
Detector Response ◽  
Neutron Energy Spectrum ◽  
True Source ◽  
Adjoint Transport

Neutrons from an atmospheric nuclear explosion can be detected by sensors in orbit. Current tools for characterizing the neutron energy spectrum assume a known source and use forward transport to recreate the detector response. In realistic scenarios the true source is unknown, making this an inefficient, iterative approach. In contrast, the adjoint approach directly solves for the source spectrum, enabling source reconstruction. The time–energy fluence at the satellite and adjoint transport equation allow a Monte Carlo method to characterize the neutron source’s energy spectrum directly in a new model: the Space to High-Altitude Region Adjoint (SAHARA) model. A new adjoint source event estimator was developed in SAHARA to find feasible solutions to the neutron transport problem given the constraints of the adjoint environment. This work explores SAHARA’s development and performance for mono-energetic and continuous neutron energy sources. In general, the identified spectra were shifted towards energies approximately 5% lower than the true source spectra, but SAHARA was able to capture the correct spectral shapes. Continuous energy sources, including real-world sources Fat Man and Little Boy, resulted in identifiable spectra that could have been produced by the same distribution as the true sources as demonstrated by two-dimensional (2D) Kolmogorov–Smirnov tests.

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