A new treatment of radiation behaviour beyond one-body observables 05/2008; DOI: 10.1051/ndata:07398

ABSTRACT We propose a new treatment of radiation behaviour in transport calculations by introducing an event generator model in which we combine the nuclear data and the reaction models so as to trace all correlations of ejectiles keeping the energy and momentum conservation in a collision. By this new model, we can estimate the fluctuations around the mean values of one-body observables, for example, the deposit energy distribution in a cell, which cannot be obtained by the transport calculations based on the Boltzmann equation with the nuclear data.

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    ABSTRACT: Detailed analyses of Solar Particle Events (SPE) were performed to calculate primary and secondary particle spectra behind aluminum, at various thicknesses in water. The simulations were based on Monte Carlo (MC) radiation transport codes, MCNPX 2.7.0 and PHITS 2.64, and the space radiation analysis website called OLTARIS (On-Line Tool for the Assessment of Radiation in Space) version 3.4 (uses deterministic code, HZETRN, for transport). The study is set to investigate the impact of SPEs spectra transporting through 10 or 20 g/cm2 Al shield followed by 30 g/cm2 of water slab. Four historical SPE events were selected and used as input source spectra particle differential spectra for protons, neutrons, and photons are presented. The total particle fluence as a function of depth is presented. In addition to particle flux, the dose and dose equivalent values are calculated and compared between the codes and with the other published results. Overall, the particle fluence spectra from all three codes show good agreement, with the MC codes showing closer agreement compared to the OLTARIS results. The neutron particle fluence from OLTARIS is lower than the results from MC codes at lower energies ( ). Based on mean square difference analysis the results from MCNPX and PHITS agree better for fluence, dose and dose equivalent when compared to OLTARIS results.
    Life sciences and space research 01/2015; 4. DOI:10.1016/j.lssr.2014.12.003
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    ABSTRACT: A new theoretical model to simulate gamma de-excitation of excited nuclei, EBITEM (ENSDF-Based Isomeric Transition and isomEr production Model), is developed based on the Evaluated Nuclear Structure Data File (ENSDF), supplementary evaluated data tables, and theories. In the model, reaction products after nucleon evaporation were de-excited by using theoretical calculations if the excitation energy was higher than 3000 keV and the mass number was greater than 40 amu. Otherwise, the nuclei were de-excited based on the scheme provided in the ENSDF. Thus by tracking nuclear de-excitation, production of prompt gamma-rays and isomers was simulated. The model is applicable for neutron capture products and spallation products of 1071 nuclear species from Li to Bk. Except for some of the light nuclei with discrete level structure, simulated isomer production and prompt gamma-ray spectra agree generally within 40% and a factor of 3, respectively.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 04/2014; 325:35–42. DOI:10.1016/j.nimb.2014.02.007 · 1.19 Impact Factor
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    ABSTRACT: A new phenomenological approach is developed to reproduce the stochastic distributions of secondary particle energy and angle with conservation of momentum and energy in reactions ejecting more than one ejectiles using inclusive cross-section data. The summation of energy and momentum in each reaction is generally not conserved in Monte-Carlo particle transport simulation based on the inclusive cross-sections because the particle correlations are lost in the inclusive cross-section data. However, the energy and angular distributions are successfully reproduced by randomly generating numerous sets of secondary particle configurations which are compliant with the conservation laws, and sampling one set considering their likelihood. This developed approach was applied to simulation of (n,xn) reactions (x Z 2) of various targets and to other reactions such as (n,np) and (n,2nα). The calculated secondary particle energy and angular distributions were compared with those of the original inclusive cross-section data to validate the algorithm. The calculated distributions reproduce the trend of original cross-section data considerably well especially in case of heavy targets. The developed algorithm is beneficial to improve the accuracy of event-by-event analysis in particle transport simulation. & 2014 Elsevier B.V. All rights reserved.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 07/2014; 763. DOI:10.1016/j.nima.2014.06.088 · 1.32 Impact Factor