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Lee A Bernstein

Publications and source records attributed to Lee A Bernstein.

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Using Neural Networks to Accelerate TALYS-2.0 Nuclear Reaction Simulations

Recent efforts to improve the predictability of TALYS-2.0 calculated charged-particle residual product cross sections have focused on adjusting parameters related to the optical model potential and pre-equilibrium process. Although adjusted TALYS-2.0 outputs show marked improvements in agreement with experimental data over the default parameters, the procedure is generally time-consuming due to the need for sequential TALYS-2.0 calculations. Since the models and model parameters must be defined and constrained prior to adjustment, we show in this work that an artificial neural network can serve as a surrogate model to successfully predict TALYS-2.0 outputs within this domain of input parameters. No practical differences were observed in the trained model's performance between uniform random, Latin hypercube and Sobol sequence sampling for generating the training datasets. Once validated, trained neural network models were used to adjust TALYS-2.0 nuclear model parameters, where a multi-parameter fitting procedure was not only feasible but optimal for this process. The neural network approach is >1000x faster at generating residual product cross sections than using TALYS-2.0 directly, and a high-fidelity surrogate model could be implemented with about 1500 TALYS-2.0 files to achieve adjusted cross sections comparable to the previous publication.

physics.comp-ph

An Integral Experiment on Polyethylene Using Radiative Capture in Indium Foils in a High Flux D-D Neutron Generator

The Department of Nuclear Engineering, University of California Berkeley built a D-D neutron generator called the High Flux Neutron Generator (HFNG). It operates in the range of 100-125 keV of accelerating voltage. The generator produces neutron current of about 10^8 per second. These neutrons have energies between 2.2-2.8 MeV. We report here the results of a measurement of the scattered vs unscattered neutron fluence on polyethylene determined via neutron activation of multiple natural indium foils from a D-D neutron generator. Both the angle-integrated spectrum and the angle differential results are consistent with the predictions of the Monte Carlo N-Particle Transport (MCNP) code, using the ENDF/B-VII.1. This supports shielding calculations in the fast energy region with high density polyethylene (HDPE). To the best of our knowledge no integral benchmark experiment has been performed on polyethylene using D(D,n)alpha neutron spectrum.

nucl-ex

$^{137,138,139}$La($n$, $γ$) cross sections constrained with statistical decay properties of $^{138,139,140}$La nuclei

The nuclear level densities and $γ$-ray strength functions of $^{138,139,140}$La were measured using the $^{139}$La($^{3}$He, $α$), $^{139}$La($^{3}$He, $^{3}$He$^\prime$) and $^{139}$La(d, p) reactions. The particle-$γ$ coincidences were recorded with the silicon particle telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these experimental results, the low-energy enhancement in the A$\sim$140 region is discussed. The $^{137,138,139}$La($n, γ)$ cross sections were calculated at $s$- and $p$-process temperatures using the experimentally measured nuclear level densities and $γ$-ray strength functions. Good agreement is found between $^{139}$La($n, γ)$ calculated cross sections and previous measurements.

nucl-ex