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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Differential and total cross sections and astrophysical S-factors for {sup 2}H(d,n){sup 3}He and {sup 2}H(d,p){sup 3}H reactions in a wide energy range

Differential cross sections of deuteron–deuteron fusion reactions are needed in astrophysics, precision cosmology, nuclear physics, and controlled nuclear fusion research. New parametrizations for center of mass differential cross sections, total cross sections and astrophysical S-factors in a wide range of specific energy from 0.5 keV/u to about 0.5 GeV/u have been obtained. Straightforward approximating formulae readily suitable for multithreaded algorithmization are given here for {sup 2}H(d,n){sup 3}He and {sup 2}H(d,p){sup 3}H reactions. The energy range is about two orders of magnitude broader than that in the tables published earlier for neutron branch.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Microscopic K{sup +}-nucleus optical potential and calculations of differential elastic-scattering cross sections and total reaction cross sections

The differential elastic-scattering cross sections and the total reaction cross sections for the interaction of K{sup +} mesons with {sup 12}C and {sup 40}Ca nuclei at beam momenta of 0.635, 0.715, and 0.8 GeV/c are calculated. The microscopic optical potential derived in the high-energy approximation is used in these calculations. It is determined by the amplitude for kaon-nucleon scattering and the density distribution of pointlike nucleons of the target nucleus. In the high-energy approximation, the Klein-Gordon-Fock equation reduces to the form of the Schroedinger equation. It is shown that small distinctions between the reduction methods do not lead to significant changes in differential elastic-scattering cross sections, but the effects of relativization as such are quite large. Good agreement with experimental data on elastic K{sup +}A scattering is attained. The total reaction cross sections can be described upon adding, to the volume potential, a term that takes the form of its derivative and which has a maximum at the periphery, its contribution being fitted to experimental data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2008

Nucleon-Nucleon Total Cross Section

The total proton-proton and neutron-proton cross sections currently used in the transport code HZETRN show significant disagreement with experiment in the GeV and EeV energy ranges. The GeV range is near the region of maximum cosmic ray intensity. It is therefore important to correct these cross sections, so that predictions of space radiation environments will be accurate. Parameterizations of nucleon-nucleon total cross sections are developed which are accurate over the entire energy range of the cosmic ray spectrum.

Norbury, John W.↗
DOE OSTI2016

Measurement of the total cross section from elastic scattering in pp collisions at s = 8 TeV with the ATLAS detector

A measurement of the total ppcross section at the LHC at √s=8TeV is presented. An integrated luminosity of 500 μb-1 was accumulated in a special run with high-β beam optics to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the -t range from 0.014GeV2 to 0.1GeV2 to extrapolate t→0, the total cross section, σtot(pp →X), is measured via the optical theorem to be σtot(pp→ X) = 96.07±0.18 (stat.)±0.85 (exp.)± 0.31 (extr.) mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation t→0. In addition, the slope of the exponential function describing the elastic cross section at small t is determined to be B =19.74 ±0.05 (stat.) ±0.23 (syst.) GeV-2.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Direct Total Cross Section Measurement of the 16O(α,γ)20Ne Reaction at Ec.m. = 2.26 MeV

In stellar helium burning, (16)O represents the endpoint of the helium-burning sequence due to the low rate of (16)O(alpha,gamma)(20)Ne. We present a new direct measurement of the total capture reaction rate of (16)O(alpha,gamma)(20)Ne at E(c.m.) = 2.26MeV employing the DRAGON recoil separator. For the first time, the total S factor and its contributing direct capture transitions could be determined in one experiment.

Hager, Ulrike↗
NASA NTRS1990

Total cross sections for positrons scattered elastically from helium based on new measurements of total ionization cross sections

An improved technique is presented for employing the 2.3m spectrometer to measure total ionization cross sections, Q sub ion, for positrons incident on He. The new ionization cross section agree with the values reported earlier. Estimates are also presented of total elastic scattering cross section, Q sub el, obtained by subtracting from total scattering cross sections, Q sub tot, reported in the literature, the Q sub ion and Q sub Ps (total positronium formation cross sections) and total excitation cross sections, Q sub ex, published by another researcher. The Q sub ion and Q sub el measured with the 3m high resolution time-of-flight spectrometer for 54.9eV positrons are in accord with the results from the 2.3m spectrometer. The ionization cross sections are in fair agreement with theory tending for the most part to be higher, especially at 76.3 and 88.5eV. The elastic cross section agree quite well with theory to the vicinity of 50eV, but at 60eV and above the experimental elastic cross sections climb to and remain at about 0.30 pi a sub o sq while the theoretical values steadily decrease.

Diana, L. M.↗
NASA NTRS1993

Ab initio method for calculating total cross sections

A method for calculating total cross sections without formally including nonelastic channels is presented. The idea is to use a one channel T-matrix variational principle with a complex correlation function. The derived T matrix is therefore not unitary. Elastic scattering is calculated from T-parallel-squared, but total scattering is derived from the imaginary part of T using the optical theorem. The method is applied to the spherically symmetric model of electron-hydrogen scattering. No spurious structure arises; results for sigma(el) and sigma(total) are in excellent agreement with calculations of Callaway and Oza (1984). The method has wide potential applicability.

Bhatia, A. K.↗
NASA NTRS2009

Pion Total Cross Section in Nucleon - Nucleon Collisions

Total cross section parameterizations for neutral and charged pion production in nucleon - nucleon collisions are compared to experimental data over the projectile momentum range from threshold to 300 GeV. Both proton - proton and proton - neutron reactions are considered. Overall excellent agreement between parameterizations and experiment is found, except for notable disagreements near threshold. In addition, the hypothesis that the neutral pion production cross section can be obtained from the average charged pion cross section is checked. The theoretical formulas presented in the paper obey this hypothesis for projectile momenta below 500 GeV. The results presented provide a test of engineering tools used to calculate the pion component of space radiation.

Norbury, John W.↗
DOE OSTI2015

Elastic and total cross sections for simple biomolecules in the intermediate energy range

The elastic and total cross sections for formaldehyde, acetaldehyde, acetone, 2-butanone and formamide are calculated using the spherical complex optical potential formalism in the intermediate energy range from 50 eV to 10 keV. These cross sections find application to various fields like radiation damage and biological sciences. The present results are compared with the available experimental and theoretical data and are found to give excellent agreement. The elastic cross sections reported for most of the targets in the present energy range are done for the first time. The energy dependence of the contribution of ionization and elastic cross section with respect to the total cross section and the correlation of total cross section with polarizability of the molecules are also studied.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Electron impact rotationally elastic total cross section for formamide

This paper reports computational results of the total cross sections for electron impact on formamide (HCONH₂) over a wide range of energies from 0.01 eV to 5 keV. Total cross sections over such a wide range are reported for the first time as the earlier reported data is up to maximum of 12 eV. Below ionization threshold of the target, we performed ab initio calculations using UK molecular R-Matrix code within static, exchange plus polarization (SEP), and close coupling approximations. Twenty eight target states are included in close coupling formalism. Total 350 channels and 2410 configuration state functions are included in the calculations. We observe a π* shape resonance at 3.41 eV and a σ* resonance at 15.3 eV as against similar resonances reported at 3.77 eV and 14.9 eV, respectively, by Goumans et al. [J. Chem. Theory Comput. 5, 217 (2009)] using SEP model. The cross sections at higher energies are evaluated using the spherical complex optical potential formalism. The two methods are found to be consistent with a smooth cross over at 18 eV. The vertical excitation energies, electronic excitation cross sections, differential cross sections, momentum transfer, and total cross sections are computed. In absence of experimental data, we compared our computed total cross sections with available other theoretical results.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Isotopically resolved neutron total cross sections at intermediate energies

The neutron total cross sections σ tot of 16,18 O, 58 64 Ni, 103 Rh, and 112,124 Sn have been measured at the Los Alamos Neutron Science Center from low to intermediate energies (3 ≤ E lab ≤ 450 MeV) by leveraging wave-form-digitizer technology. The σ tot relative differences between isotopes are presented, revealing additional information about the isovector components needed for an accurate optical-model description away from stability. Digitizer-enabled σ tot -measurement techniques are discussed and a series of uncertainty-quantified dispersive optical model (DOM) analyses using these new data is presented, validating the use of the DOM for modeling light systems ( 16,18 O) and systems with open neutron shells ( 58,64 Ni and 112,124 Sn). Here, the valence-nucleon spectroscopic factors extracted for each isotope reaffirm the usefulness of high-energy proton reaction cross sections for characterizing depletion from the mean-field expectation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2014

New Opportunity for Improved Nuclear Forensics, Radiochemical Diagnostics, and Nuclear Astrophysics: Need for a Total-Cross-Section Apparatus at the LANSCE

Total-cross-section measurements are feasible on a much wider range of radioactive samples than (n,γ) cross-section measurements, and information extracted from the former can be used to set tight constraints on the latter. There are many (n,γ) cross sections of great interest to radiochemical diagnostics, nuclear forensics, and nuclear astrophysics which are beyond the reach of current direct measurement, that could be obtained in this way. Our simulations indicate that measurements can be made at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center for samples as small as 10μg. There are at least 40 high-interest nuclides which should be measurable, including 88 Y, 167,168,170,171 Tm, 173,174 Lu, and 189,190,192 Ir.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2010

Threshold photoelectron source for the study of low-energy electron scattering: Total cross section for electron scattering from krypton in the energy range from 14 meV to 20 eV

An experimental technique for the measurement of the total cross section for electron scattering from atoms and molecules at high resolution is described. The total cross sections for electron scattering from Kr in the energy range from 14 meV to 20 eV obtained with the technique are also reported. The present technique employs a combination of the penetrating field technique and the threshold photoionization of rare-gas atoms using synchrotron radiation as an electron source in order to produce a high-resolution electron beam at very low energy. The characteristics of the electron sources were determined by measuring the ionizing photon energy dependence of photoelectron yield. Absolute total cross sections for electron scattering are obtained by the attenuation method. The measured absolute values of the total cross sections for electron scattering from Kr agree with those obtained by other groups down to 175 meV, above which several experimental works have been reported. Below 175 meV, the present results generally agree with theoretical cross sections down to 14 meV. The resonant structures in the total cross sections due to Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 3/2}) and the Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 1/2}) Feshbach resonances are also reported. The resolution of the present setup has been estimated from a fit of the measured profile of the Kr{sup -} (4p{sup 5}5s{sup 2} {sup 2}P{sub 3/2}) resonance by the theoretical curve obtained from the resonant scattering theory.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

High-resolution total-cross-section measurements for electron scattering from Ar, Kr, and Xe employing a threshold-photoelectron source

Absolute total cross sections for electron scattering from Ar and Xe at electron energies ranging from 7 meV to 20 eV were obtained with the experimental technique employing the threshold-photoelectron source. The measured total cross sections are in good agreement with those obtained by other groups down to 100 meV, above which several experimental works have been reported. Scattering lengths for electron scattering from Ar, Kr, and Xe were determined from the present total cross sections and our recent results for Kr using the modified effective range theory. The values of the scattering length obtained in the present analysis differ from the values determined from the previous swarm experiments and beam experiments. The resonant structures in the total cross sections due to Feshbach resonances of Ar, Kr, and Xe with an improved energy resolution were also measured. Analyses of the resonant structure were carried out based on the spin-dependent resonant scattering theory in order to determine the values of the natural width of Feshbach resonances of Ar, Kr, and Xe precisely.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

The γ{sup *}γ{sup *} total cross section in NLA BFKL

We study the γ{sup *}γ{sup *} total cross section in the NLA BFKL approach. We have extracted the NLO corrections to the photon impact factor from two recent papers of Balitsky and Chirilli and Chirilli and Kovchegov and used them to build several representations of the total cross section, equivalent within the NLA. We have combined these different representations with two among the most common methods for the optimization of a perturbative series, namely PMS and BLM, and compared their behavior with the energy with the only available experimental data, those from the LEP2 collider.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Experimental Results on Ultrahigh-Energy Cosmic Rays and Asymptotic Behavior of the Total Cross Section for Nucleon–Nucleon Interaction

Results obtained by studying the energy dependence of the total cross section for nucleon–nucleon interaction are presented. The analytic parametrization proposed within axiomatic quantum field theory describes quantitatively a unified set of experimental data on proton–proton and antiproton–proton scattering. At collision energies above 86 GeV, the parameter values fitted to subsets of all available data and accelerator data alone were found to deviate from the respective asymptotic values. This indicates that the Froissart–Martin limit for the total cross section has not yet been reached in the case of these subsets. An approximation of the total nucleon–nucleon cross section measured in cosmic rays leads for some parameters to fitted values that, within 1.0 to 1.3 standard deviations, agree with the respective asymptotic values. This resultmay be viewed as an indication of the beginning of the asymptotic functional behavior of the total nucleon–nucleon cross section measured in cosmic rays of ultrahigh energy O(100 TeV). This is confirmed within the color glass condensate approach.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1989

Improved calculation of total cross section for pair production by relativistic heavy ions

A calculation of the total cross section for direct electron-positron pair production by heavy ions is described. It combines the use of the Weizsaecker-Williams method for low-energy transfers and existing calculations for high-energy transfers. Higher-order corrections to the total cross section are calculated based on the Weizsaecher-Williams method and existing results for pair production by photons.

Eby, P. B.↗