Design and verification of a multi-layer single-sphere neutron spectrometer with water as the moderator

Abstract Measuring the neutron energy spectrum is important in nuclear radiation detection and protection. Common neutron spectrometers include the Bonner sphere spectrometer (BSS), time-of-flight neutron spectrometer, and plastic scintillation detector. Among them, the BSS is the most widely used for its wide measurement range and simple operation. A BSS usually occupies a large space because it contains several independent spheres working at the same time, leading to poor consistency. This paper proposes a multi-layer single-sphere spectrometer using water as the moderator. The spectrometer includes a multi-layered sphere that can be filled with water or air and a ^3He proportional counter placed in the center of the sphere. To verify the feasibility of this design, we use Geant4 to calculate the moderating ability of water and the response functions of the multi-layer single-sphere spectrometer. Additionally, several standard neutron energy spectra (from IAEA) are used to test the response characteristics of this spectrometer through simulation. The simulation results prove the feasibility of the design. This research provides a theoretical basis for a multi-layer single-sphere neutron spectrometer with water as the moderator.

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Finite temperature effect on knock-on ion production and neutron energy spectrum in deuteron–triton fusion plasma

Journal of Plasma Physics ◽

10.1017/s0022377806005885 ◽

2006 ◽

Vol 72 (06) ◽

pp. 1179 ◽

Cited By ~ 1

Author(s):

M. NAKAMURA ◽

Y. NAKAO

Keyword(s):

Energy Spectrum ◽

Temperature Effect ◽

Neutron Energy ◽

Finite Temperature ◽

Neutron Energy Spectrum ◽

Fusion Plasma ◽

Ion Production

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Space to Air High-Altitude Region Adjoint Neutron Transport

The Journal of Defense Modeling and Simulation Applications Methodology Technology ◽

10.1177/15485129211031669 ◽

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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