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Results for “elastic cross sections”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Complete quantification of parametric uncertainties in ( d , p ) transfer reactions

Deuteron-induced transfer reactions are a popular probe in nuclear structure and nuclear astro physics studies. The interpretation of these transfer measurements relies on reaction theory that takes as input effective interactions between the nucleons and the target nucleus. Previous work quantified the uncertainty associated with the optical potentials between the nucleons and the target. In this study, we extend that work by also including the parameters of the mean field associated with the overlap function of the final bound state, thus obtaining the full parametric uncertainty on transfer observables. We use Bayesian Markov Chain Monte Carlo simulations to obtain parameter posterior distributions. We use elastic-scattering cross sections to constrain the optical potential parameters and use the asymptotic normalization coefficient of the final state to constrain the bound state interaction. We then propagate these posteriors to the transfer angular distributions and obtain confidence intervals for this observable. We study (d,p) reactions on 14 C, 16 O, and 48 Ca at energies in the range $E$ $d$ = 7 - 24 MeV. Our results show a strong reduction in uncertainty by using the asymptotic normalization coefficient as a constraint, particularly for those reactions most sensitive to ambiguities in the mean field. For those reactions, the importance of constraining the bound state interaction is equal to that of constraining the optical potentials. Furthermore, the case of 14 C is an outlier because the cross section is less sensitive to the nuclear interior. When minimal constraints are used on the parameters of the nucleon-target interaction, the 1σ uncertainties on the differential cross sections are large (~ 500-100%). However, if elastic-scattering data and the asymptotic normalization coefficient are used in the analysis, with an error of 10% (5%), this uncertainty reduces to ~ 30% (~ 15%).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2001

Monte Carlo track structure for radiation biology and space applications

Over the past two decades event by event Monte Carlo track structure codes have increasingly been used for biophysical modelling and radiotherapy. Advent of these codes has helped to shed light on many aspects of microdosimetry and mechanism of damage by ionising radiation in the cell. These codes have continuously been modified to include new improved cross sections and computational techniques. This paper provides a summary of input data for ionizations, excitations and elastic scattering cross sections for event by event Monte Carlo track structure simulations for electrons and ions in the form of parametric equations, which makes it easy to reproduce the data. Stopping power and radial distribution of dose are presented for ions and compared with experimental data. A model is described for simulation of full slowing down of proton tracks in water in the range 1 keV to 1 MeV. Modelling and calculations are presented for the response of a TEPC proportional counter irradiated with 5 MeV alpha-particles. Distributions are presented for the wall and wall-less counters. Data shows contribution of indirect effects to the lineal energy distribution for the wall counters responses even at such a low ion energy.

NASA Center JSC↗
NASA NTRS1985

Differential scattering cross sections for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2

This paper reports the first results of an experimental program established to provide cross section data for use in modeling various atmospheric processes. Absolute cross sections, differential in the scattering angle, have been measured for collisions of 0.5-, 1.5-, and 5.0-keV helium atoms with He, H2, N2, and O2 at laboratory scattering angles between 0.1 deg and 5 deg. The results are the sums of cross sections for elastic and inelastic scattering of helium atoms; charged collision products are not detected. Integration of the differential cross section data yields integral cross sections consistent with measurements by other workers. The apparatus employs a position-sensitive detector for both primary and scattered particles and uses a short target cell with a large exit aperture to ensure a simple and well-defined apparatus geometry.

Newman, J. H.↗
DOE OSTI2022

An iron evaluation story: from TALYS model parameters to validation on the ASPIS benchmark with the Monte-Carlo code TRIPOLI-4

Iron is a widespread structural material in nuclear applications. However some benchmark studies show that for many libraries, including TENDL-2019, producing good iron evaluations is still an open challenge. This work aims at improving TENDL-2019 {sup 56}Fe and {sup 54}Fe evaluations through feedbacks from experimental data and Monte Carlo results of the iron benchmark ASPIS. Part of the T6 code infrastructure was used to produce the evaluations. In the new evaluations, particular attention to resonance parameters and formalism was paid to address the importance of elastic scattering. The total inelastic scattering and inelastic continuum cross sections were shaped by modifying the input parameters of TALYS, one of the T6 codes. Additionally, it was necessary to normalise some reaction channels to those of JENDL-4.0. With the new files ASPIS results, obtained with the Monte Carlo code TRIPOLI-4, improved noticeably compared to TENDL 2019. The evaluations and parameter setting modifications are to be included into TENDL-2021. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1991

Studies of electron collisions with polyatomic molecules using distributed-memory parallel computers

Elastic electron scattering cross sections from 5-30 eV are reported for the molecules C2H4, C2H6, C3H8, Si2H6, and GeH4, obtained using an implementation of the Schwinger multichannel method for distributed-memory parallel computer architectures. These results, obtained within the static-exchange approximation, are in generally good agreement with the available experimental data. These calculations demonstrate the potential of highly parallel computation in the study of collisions between low-energy electrons and polyatomic gases. The computational methodology discussed is also directly applicable to the calculation of elastic cross sections at higher levels of approximation (target polarization) and of electronic excitation cross sections.

Winstead, C.↗
DOE OSTI2022

Elastic Electron Scattering From Mirror Nuclei 3He and 3H

The primary aim of my work is the extraction of the elastic cross-sections from data collected in Jefferson Lab Hall A experiment E12-11-112 which measured inclusive elastic scattering from the mirror nuclei 3He and 3H at low momentum transfer Q2 ? 0.1 GeV2. The obtained 3H cross-section is 0.630 ± 0.027 ?barn/sr with fractional uncertainty 4.35% and 3He cross- section is 1.274 ± 0.055 ?barn/sr with fractional uncertainty 4.29% . I determined the ratio of the 3He and 3H cross-sections since it cancels many of the systematic uncertainties that enter into the absolute cross-section extraction, and it reduced the fractional uncertainty to 1.85%.

Kurbany, Leiqaa↗
NASA NTRS1988

Nucleon-nucleus interaction data base: Total nuclear and absorption cross sections

Neutron total cross sections are represented for Li to Pu targets at energies above 0.1 MeV and less than 100 MeV using a modified nuclear Ramsauer formalism. The formalism is derived for energies above 100 MeV by fitting theoretical cross sections. Neutron absorption cross sections are represented by analytic expressions of similar form, but shape resonance phenomena of the Ramsauer effect is not present. Elastic differential cross sections are given as a renormalized impulse approximation. These cross section data bases are useful for nucleon transport applications.

Wilson, J. W.↗
NASA NTRS2006

Low-Energy Elastic Electron Scattering by Atomic Oxygen

The B-spline R-matrix method is employed to investigate the low-energy elastic electron scattering by atomic oxygen. Flexible non-orthogonal sets of radial functions are used to construct the target description and to represent the scattering functions. A detailed investigation regarding the dependence of the predicted partial and total cross sections on the scattering model and the accuracy of the target description is presented. The predicted angle-integrated elastic cross sections are in good agreement with experiment, whereas significant discrepancies are found in the angle-differential elastic cross sections near the forward direction. .The near-threshold results are found to strongly depend on the treatment of inner-core short-range correlation effects in the target description, as well as on a proper account of the target polarizability. A sharp increase in the elastic cross sections below 1 eV found in some earlier calculations is judged to be an artifact of an unbalanced description of correlation in the N-electron target structure and the (N+l)-electron-collision problems.

Zatsarinny O.↗
NASA NTRS1986

Studies of electron-molecule collisions - Applications to e-H2O

Elastic differential and momentum transfer cross sections for the elastic scattering of electrons by H2O are reported for collision energies from 2 to 20 eV. These fixed-nuclei static-exchange cross sections were obtained using the Schwinger variational approach. In these studies the exchange potential is directly evaluated and not approximated by local models. The calculated differential cross sections, obtained with a basis set expansion of the scattering wave function, agree well with available experimental data at intermediate and larger angles. As used here, the results cannot adequately describe the divergent cross sections at small angles. An interesting feature of the calculated cross sections, particularly at 15 and 20 eV, is their significant backward peaking. This peaking occurs in the experimentally inaccessible region beyond a scattering angle of 120 deg. The implication of this feature for the determination of momentum transfer cross sections is described.

Brescansin, L. M.↗
DOE OSTI2022

Characterisation of the dip-bump structure observed in proton–proton elastic scattering at $\sqrt{s}$ = 8 TeV

The TOTEM collaboration at the CERN LHC has measured the differential cross-section of elastic proton–proton scattering at √s = 8TeV in the squared four-momentum transfer range 0.2GeV 2 < |t| < 1.9GeV 2 . This interval includes the structure with a diffractive minimum (“dip”) and a secondary maximum (“bump”) that has also been observed at all other LHC energies, where measurements were made. A detailed characterisation of this structure for √s = 8 TeV yields the positions, |t| dip = (0.521 ± 0.007)GeV 2 and |t| bump = (0.695 ± 0.026)GeV 2 , as well as the cross-section values, dσ/dt| dip = (15.1 ± 2.5)μb/GeV 2 and dσ/dt| bump = (29.7 ± 1.8)μb/GeV 2 , for the dip and the bump, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1978

Model potentials for electron scattering - Converged close coupling calculations for the differential cross section for e/-/N2 at 30-50 eV

A calculation has been made of the elastic scattering and rotational excitation cross sections for e(-)-N2 scattering at 30 and 50 eV using quantum chemical techniques specially designed to be applicable to elastic and inelastic electron scattering by general polyatomic molecules. The angle dependence of the sum of the elastic and rotational excitation differential cross sections is in good agreement with experiment at all scattering angles at both energies, but at 50 eV the difference from experiment exceeds the experimental uncertainty at small scattering angles and near the minimum of the differential cross section. At large scattering angles the rotational excitation cross sections are predicted to exceed the elastic scattering cross sections. The absolute cross sections agree with experiment at some angles but at other angles are as much as 51% (30 eV) or 90% (50 eV) higher; this may be due at least in part to the difficulty of putting the experimental results on an absolute scale.

Onda, K.↗