Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

ALPHANSO: Open-Source Modeling of ($α$,n) Neutron Source Terms

Anthony J. Nelson, Divit Rawal, William Zywiec, Daniel Siefman

Abstract

Applications ranging from nuclear safeguards to dark matter detection require accurate predictions of neutron fields produced by ($α$,n) reactions. Legacy tools like SOURCES-4C remain widely used but suffer from significant limitations, including outdated nuclear data, missing target nuclides, and restricted accessibility. Here, we present ALPHANSO, an open-source Python package for calculating ($α$,n) neutron source terms. ALPHANSO incorporates modern nuclear data libraries and formats covering all naturally occurring target nuclides and provides a transparent, modular framework for updating or extending the data as new evaluations are released. Comparison with SOURCES-4C and experimental measurements across a range of elements and materials shows that ALPHANSO reproduces neutron yields and spectra that typically match or exceed the accuracy of existing codes. These results demonstrate that ALPHANSO is a reliable, accessible, modern replacement for legacy ($α$,n) source term codes. Its open-source design and modular data handling make it readily extensible to future evaluated nuclear data and low-background applications.

ALPHANSO: Open-Source Modeling of ($α$,n) Neutron Source Terms

Abstract

Applications ranging from nuclear safeguards to dark matter detection require accurate predictions of neutron fields produced by (,n) reactions. Legacy tools like SOURCES-4C remain widely used but suffer from significant limitations, including outdated nuclear data, missing target nuclides, and restricted accessibility. Here, we present ALPHANSO, an open-source Python package for calculating (,n) neutron source terms. ALPHANSO incorporates modern nuclear data libraries and formats covering all naturally occurring target nuclides and provides a transparent, modular framework for updating or extending the data as new evaluations are released. Comparison with SOURCES-4C and experimental measurements across a range of elements and materials shows that ALPHANSO reproduces neutron yields and spectra that typically match or exceed the accuracy of existing codes. These results demonstrate that ALPHANSO is a reliable, accessible, modern replacement for legacy (,n) source term codes. Its open-source design and modular data handling make it readily extensible to future evaluated nuclear data and low-background applications.
Paper Structure (12 sections, 9 equations, 6 figures, 3 tables)

This paper contains 12 sections, 9 equations, 6 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Data
  3. ($\alpha$,n) Cross Sections
  4. Stopping Power
  5. Methodology
  6. Results
  7. Monoenergetic Beam Yield
  8. Neutron Emission Spectra
  9. Homogeneous Mixtures
  10. Impact of Data Sources
  11. Conclusion
  12. Acknowledgments and Funding

Figures (6)

  • Figure 1: ($\alpha$,n) cross sections from ENDF/B-VIII.1, JENDL-5, TENDL-2023, SOURCES-4A, and SOURCES-4C for selected nuclides.
  • Figure 2: Stopping power from ASTAR, SRIM, and SOURCES-4A/SOURCES-4C for selected elements. Note that SOURCES-4A and SOURCES-4C have identical stopping powers, plotted as "SOURCES".
  • Figure 3: Neutron yields from ALPHANSO, SOURCES-4A, SOURCES-4C, and experimental data for $\alpha$-beams incident on selected nuclides. Experimental data taken from west_measurements_1982.
  • Figure 4: Normalized pectra and yield ($Y$) from ALPHANSO, SOURCES-4A, and SOURCES-4C, and experimental data for selected nuclides.
  • Figure 5: Calculated-to-Experimental neutron yield ratios and Mean Absolute Error (MAE) for ($\alpha$,n) reactions on light elements for the emission spectra of $^{235}$U and $^{238}$U $\alpha$ decay series in secular equilibrium. MAE is computed across all targets for ALPHANSO and SOURCES-4A and for all targets, excluding Fe, for SOURCES-4C.
  • ...and 1 more figures