High Energy Coupled Nucleon Tranpsort in One Dimension

The problem of energetic nucleon transport through extended bulk matter is considered in the context of the \u27straight ahead\u27 approximation. The applicable form of the Boltzmann transport equation is derived and solved in one dimension. The production term for secondary generation nucleons due to nuclear fragmentation includes \u27coupling\u27 of the flux to other types of nucleon projectiles. A physically motivated perturbation series approach is developed to enhance solution convergence. The Boltzmann operator is inverted and the flux is computed using a numerical marching scheme. The secondary production integrals are optimized for second order accuracy using a set of analytical benchmarks. The benchmarks provide precise estimation of the truncation errors involved in the numerical method. A set of continuous benchmarks are developed for cosmic ray transport applications and a set of mono-energetic benchmarks is developed for accelerator applications. The optimized marching scheme is incorporated into the BRYNTRN transport code along with a sophisticated reaction database for nuclear and atomic scattering. The method is applied to typical space shielding applications and comparisons are made with the HETC Monte Carlo benchmarks. The BRYNTRN results compare well with HETC while requiring significantly less computing power. The transport of elastically scattered neutrons is shown to be poorly converged using the coarse energy grids suited to non-elastic scattering. A grid independent model is developed for neutron elastic scattering which maintains particle conservation to within acceptable limits for deep penetration transport cases. The elastic scattering model is applied to a range of shielding cases

Benchmark solutions for the galactic heavy-ion transport equations with energy and spatial coupling

Nontrivial benchmark solutions are developed for the galactic heavy ion transport equations in the straightahead approximation with energy and spatial coupling. Analytical representations of the ion fluxes are obtained for a variety of sources with the assumption that the nuclear interaction parameters are energy independent. The method utilizes an analytical LaPlace transform inversion to yield a closed form representation that is computationally efficient. The flux profiles are then used to predict ion dose profiles, which are important for shield design studies

A Hierarchy of Transport Approximations for High Energy Heavy (HZE) Ions

The transport of high energy heavy (HZE) ions through bulk materials is studied neglecting energy dependence of the nuclear cross sections. A three term perturbation expansion appears to be adequate for most practical applications for which penetration depths are less than 30 g per sq cm of material. The differential energy flux is found for monoenergetic beams and for realistic ion beam spectral distributions. An approximate formalism is given to estimate higher-order terms

HZETRN: A heavy ion/nucleon transport code for space radiations

The galactic heavy ion transport code (GCRTRN) and the nucleon transport code (BRYNTRN) are integrated into a code package (HZETRN). The code package is computer efficient and capable of operating in an engineering design environment for manned deep space mission studies. The nuclear data set used by the code is discussed including current limitations. Although the heavy ion nuclear cross sections are assumed constant, the nucleon-nuclear cross sections of BRYNTRN with full energy dependence are used. The relation of the final code to the Boltzmann equation is discussed in the context of simplifying assumptions. Error generation and propagation is discussed, and comparison is made with simplified analytic solutions to test numerical accuracy of the final results. A brief discussion of biological issues and their impact on fundamental developments in shielding technology is given

Benchmark Solutions for the Galactic Heavy-Ion Transport . . .

(Maximum 200 words) Nontrivial benchmark solutions are developed for the galactic heavy-ion transport equations in the straightahead approximation with energy and spatial coupling. Analytical representations of the ion fluxes are obtained for a variety of sources with the assumption that the nuclear interaction parameters are energy independent. The method utilizes an analytical Laplace transform inversion to yield a closed-form representation that is computationally efficient. The flux profiles are then used to predict ion dose profiles, which are important for shield-design studies. 14. SUBJECT TERMS 15. NUMBER OF PAGES Benchmark solutions; Space radiation; Heavy-ion transport 55 16. PRICE CODE A04 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF REPORT OF THIS PAGE OF ABSTRACT OF ABSTRACT Unclassified Unclassified NSN 7540-01-280-5500 Standard Form 298(Rev. 2-89) Prescribed by ANSI Std. Z39-18 298-102 NASA-Langley, The u..

11. SUPPLEMENTARY NOTES 5. FUNDING NUMBERS

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11. SUPPLEMENTARY NOTES

OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of thi