SEARCH · Search NASA

Results for “section”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18

All sources NASA NTRS DOE OSTI

NASA NTRSDate not supplied

PIV Measurements of Shock-Wave/Boundary-Layer Interactions at Mach 2.5 in a Circular Test Section

The particle image velocimetry (PIV) measurement technique has been applied to make detailed measurements in an impinging shock-wave/boundary-layer interaction (SWBLI) flowfield in a test section of circular cross-section. By virtue of this test section geometry, the flowfields studied are free from effects of the complex coupling of sidewall and corner interaction into the primary impinging shock interaction typical of a rectangular test section. The cone-cylinder shock generator hardware was arranged in both coaxial alignment with the test section to generate axisymmetric SWBLIs and in offset positions to generate swept SWBLIs. The angle of the conical section was also varied to alter the strength of the impinging shock wave. The application of the PIV technique in this test section required meticulous design to provide adequate optical access without disturbing the SWBLI flow. Details of the stereoscopic PIV apparatus and the velocity measurements obtained for a Mach 2.5 freestream are presented. Key features of the mean velocity and turbulent stress fields are highlighted. This data set should enable validation of computational fluid dynamics results for these flowfields.

Shockwave Boundary Layer Interaction↗

DOE OSTI2017

Processing of hollow sections

A system and method provide a material with uniform micro-structure. In an embodiment, an equal channel angular extrusion system includes an interior mandrel. The interior mandrel includes an expanding shear material section and a contracting shear material section. In addition, the system includes a material. The material is disposed about a portion of the interior mandrel. Moreover, the system includes a pressure application device. The pressure application device applies pressure to the material to force the material to contact the expanding shear material section to provide an expanded post-shear material section. Pressure from the pressure application device applies pressure to the material to force the expanded post-shear material section to contact the contracting shear material section to provide a contracted shear material section.

42 ENGINEERING↗

DOE OSTI2022

Processing of hollow sections

Barber, Robert E.↗

DOE OSTI2021

Integral Measurement of the 237 Np($n$, γ) 238 Np Cross Section with Fast Neutrons

Accurate knowledge of the 237 Np($n$; γ) 238 Np cross section at fast neutron energies is important for applied nuclear science. The presently available experimental data has large disagreements in the fast neutron region. A measurement of the 237 Np($n$; γ) 238 Np cross section was performed using a well characterized fast neutron source and the results was compared with previous measurements and current nuclear data evaluations. This will provide an integral measurement that can be used as a benchmark for current evaluations. Multiple samples of 237 Np were irradiated in the Godiva-IV critical assembly. Following the irradiation, the samples placed in a γ-ray counting setup and the γ-rays emitted from the decay of 238 Np were measured over a time period of approximately 7 days. Multiple γ-ray decay branches of 238 Np were observed. The observed activity of 238 Np was used to calculate the amount of 238 Np produced during the irradiation via the 237 Np($n$; γ) 238 Np and an integral cross section of 359(10) mb was measured. The 238 Np half-life has been measured with a result of 50.34(7) hours. An integral measurement of the 237 Np($n$; γ) 238 Np cross section has been measured. This result has been compared to the calculated integral cross section using the ENDF/BVIII.0 and JENDL-4.0 evaluated cross sections and found to be in good agreement with ENDF/BVIII.0 value of 367 mb. The JENDL-4.0 evaluation yields a value of 312 mb, which is significantly lower than the measured cross section.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2026

Neutrino-Argon Cross Sections in MicroBooNE: Measurements Spanning Multiple Interaction Channels, Final States, and Neutrino Fluxes

Neutrinos are one of the most elusive particles in the Standard Model of particle physics due to their tiny interaction cross section, which makes them challenging to detect and study. There are three known flavors of neutrinos, and any given neutrino probabilistically oscillates between them as a function of the particle's energy and propagation distance. Experimental characterization of these oscillations elucidates fundamental properties of the neutrino and the Standard Model. Meeting the precision goals of ongoing and future oscillation measurements requires detailed modeling of the way neutrinos interact with nuclear matter. Precision modeling of these interactions is a challenging theoretical problem, rich with intricate physics effects to explore, and requires input from equally precise measurements of neutrino-nucleus interaction cross sections spanning a broad range of scattering channels. To fill this need, there is an ongoing multi-experiment effort to measure these cross sections across energies, interaction channels, and nuclear targets. This thesis describes three analyses reporting neutrino-argon cross section measurements with data from the MicroBooNE liquid argon time projection chamber detector. These span multiple interaction channels, final state topologies, and neutrino fluxes. The first analysis is a set of inclusive charged current muon neutrino cross section measurements for final states with and without protons, which provides a unique view of the hadronic final state produced in these interactions. Second is a set of cross section measurements for neutral current neutral pion production, which provides a vital dataset on this under-characterized channel. Third is significant progress on measuring neutrinos produced by kaons decaying at rest, which represents a unique opportunity to measure cross sections with a mono-energetic flux of neutrinos. These measurements are accompanied by a modeling study in the GiBUU theory framework, which probes the sensitivity of the muon neutrino and pion production measurements to the modeling of nucleon-nucleon final state interactions in neutrino-nucleus scattering.

Bogart, Benjamin [Michigan U.]↗

DOE OSTI2016

State-resolved differential and integral cross sections for the Ne + H{sub 2}{sup +} (v = 0–2, j = 0) → NeH{sup +} + H reaction

State-to-state quantum dynamic calculations for the proton transfer reaction Ne + H{sub 2}{sup +} (v = 0–2, j = 0) are performed on the most accurate LZHH potential energy surface, with the product Jacobi coordinate based time-dependent wave packet method including the Coriolis coupling. The J = 0 reaction probabilities for the title reaction agree well with previous results in a wide range of collision energy of 0.2-1.2 eV. Total integral cross sections are in reasonable agreement with the available experiment data. Vibrational excitation of the reactant is much more efficient in enhancing the reaction cross sections than translational and rotational excitation. Total differential cross sections are found to be forward-backward peaked with strong oscillations, which is the indication of the complex-forming mechanism. As the collision energy increases, state-resolved differential cross section changes from forward-backward symmetric peaked to forward scattering biased. This forward bias can be attributed to the larger J partial waves, which makes the reaction like an abstraction process. Differential cross sections summed over two different sets of J partial waves for the v = 0 reaction at the collision energy of 1.2 eV are plotted to illustrate the importance of large J partial waves in the forward bias of the differential cross sections.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2005

Integral cross sections for the direct excitation of the A 3 (sigma) u +, B 3 (pi) g, W 3 (delta) u, B' 3 (sigma) u -, a' 1 (sigma) u -, a 1 (pi) g, w 1 (delta) u, and C 3 (pi) u electronic states in

Integral cross sections for electron impact excitation out of the ground state (X 1(sigma)g +) to the A 3(sigma)u +, B 3(pi)g, W 3(delta)u, B' 3(sigma)u -, a' 1(sigma)u -, a 1(pi)g, w 1(delta)u, and states in N2 are reported at incident energies ranging between 10 and 100 eV. These data have been derived by integrating differential cross sections previously reported by this group. New differential cross section measurements for the a 1(pi)g state at 200 eV are also presented to extend the range of the reported integral cross sections for this state, which is responsible for the emissions of the Lyman-Birge-Hopfield band system (a 1(pi)g (rightwards arrow) X 1(sigma)g +). The present results are compared and critically evaluated against existing cross sec In general, the present cross sections are smaller than previous results at low impact energies from threshold through the excitation function peak regions. These lower cross sections have potentially significant implications on our understanding of UV emissions in the atmospheres of Earth and Titan.

Ultraviolet Imaging Spectograph↗

DOE OSTI2017

Kernel reconstruction methods for Doppler broadening — Temperature interpolation by linear combination of reference cross sections at optimally chosen temperatures

This paper establishes a new family of methods to perform temperature interpolation of nuclear interactions cross sections, reaction rates, or cross sections times the energy. One of these quantities at temperature T is approximated as a linear combination of quantities at reference temperatures (T j ). The problem is formalized in a cross section independent fashion by considering the kernels of the different operators that convert cross section related quantities from a temperature T 0 to a higher temperature T — namely the Doppler broadening operation. Doppler broadening interpolation of nuclear cross sections is thus here performed by reconstructing the kernel of the operation at a given temperature T by means of linear combination of kernels at reference temperatures (T j ). The choice of the L 2 metric yields optimal linear interpolation coefficients in the form of the solutions of a linear algebraic system inversion. The optimization of the choice of reference temperatures (T j ) is then undertaken so as to best reconstruct, in the L∞ sense, the kernels over a given temperature range [T min ,T max ]. The performance of these kernel reconstruction methods is then assessed in light of previous temperature interpolation methods by testing them upon isotope 238 U. Temperature-optimized free Doppler kernel reconstruction significantly outperforms all previous interpolation-based methods, achieving 0.1% relative error on temperature interpolation of 238 U total cross section over the temperature range [300 K,3000 K] with only 9 reference temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Neutron elastic and inelastic cross section measurements on silicon from 0.8--8 MeV

Neutron elastic and inelastic scattering differential cross sections were measured at angles between 30° and 155° with incident neutron energies between 0.8 and 8 MeV. The measured differential scattering cross sections are compared to existing measurements and the ENDF/B-VIII.0, the JEFF-3.3, and the JENDL-4.0 data evaluations, as well as theoretical calculations from the TALYS-1.95 nuclear reaction code. Our results are reasonably well described by values from the ENDF/B-VIII.0 and JEFF-3.3 compilations. However, below 4 MeV, our backward-angle elastic scattering results tend to be lower than database/calculated values, suggesting that less recoil damage would occur than expected. Above 6 MeV, larger backward-angle cross sections are observed suggesting the opposite. Deexcitation γ rays produced in the inelastic scattering process were also studied for neutron energies between 1.9 and 4.5 MeV. Inelastic neutron scattering cross sections deduced from 28 Si(n,n1γ) γ-ray projection cross sections confirm our 28 Si(n,n1) results. To the extent that data from GELINA and our experimental results can be compared, we have excellent agreement between the inelastic neutron scattering cross sections.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2026

59 Co(p,X) spallation reaction cross sections for 250 MeV to 2 GeV protons

Cobalt is an advantageous target for probing the physics of nuclear spallation, because it is a naturally mono-isotopic element ( 59 Co), and its per-nucleon binding energy (BE/A = 8.768 MeV) is near the maximum value for all nuclei. We measured nuclear spallation cross sections for the 59 Co(p,X) reaction at five kinetic energies ranging from 250 MeV to 2 GeV. Cross sections for the production of 58 Co, 57 Co, 57 Mn, 56 Co, 56 Mn, 56 Cr, 55 Fe, 53 Fe, 54 Mn, 52 Mn, 51 Cr, 49 Cr, 48 V, 47 Sc, 46 Sc, 44 Sc, and 44 Scm are reported. Where comparable data exist in the EXFOR reaction database, we find that our measured cross sections generally agree. In many cases, we provide data for reactions or energies not currently reported in EXFOR. Our cross sections also provide evidence for the presence of α-clusters within the 59 Co nucleus, a surprising result given the asymmetry in Z (27) and N (32) for this nucleus. Finally, we use our measurements to evaluate the accuracy of spallation cross section simulations from GEANT4-based radiation transport toolkit, performed with the INCLXX-, Bertini-, and Binary-ion-cascade (BIC) based physics lists. This benchmarking activity revealed that the simulations overestimated the cross sections by a factor of ∼2–4 on average, and that the INCL-XX physics list provides the most reliable results. This evaluation informs the selection of the GEANT4 physics lists used for the analysis of data from NASA’s Psyche mission, which will measure γ rays and neutrons resulting from spallation reactions occurring on the surface of an asteroid whose surface is thought to be rich in iron-nickel metal.

43 PARTICLE ACCELERATORS↗

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 OSTI2016

Absolute cross sections for electronic excitation of pyrimidine by electron impact

We measured differential cross sections for electron-impact electronic excitation of pyrimidine, both as a function of electron energy up to 18 eV, and of scattering angle up to 180°. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. The differential cross sections were summed to obtain integral cross sections. These are compared to results of R-matrix calculations, which successfully reproduce both the magnitude of the cross section and the major resonant features. Comparison of the experiment to the calculated contributions of different symmetries to the integral cross section permitted assignment of several features to specific core-excited resonances. Comparison of the resonant structure of pyrimidine with that of benzene revealed pronounced similarities and thus a dominant role of π–π{sup ∗} excited states and resonances. Electron energy loss spectra were measured as a preparation for the cross section measurements and vibrational structure was observed for some of the triplet states. A detailed analysis of the electronic excited states of pyrimidine is also presented.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Effects of cross-section on mechanical properties of Au nanowire

The aim of this paper is study of the effects of multiple cross-section of Au nanowire on mechanical properties. Different cross-section models of Au nanowires including circular, hexagonal, pentagonal and rectangular were simulated by finite element modeling using ABAQUS. In this study, the bending technique was applied so that both ends of the model were clamped with mid-span under loading condition. The cross-sections had the length of 400 nm and the diameter of 40 nm, except the circular cross-section while the rest of the cross-sections had an equivalent diameter. Von Misses stresses distribution were used to define the stress distribution in the cross-section under loading condition, and elastic deformation was analyzed by the beam theory. The results disclosed that the circular and the rectangular models had highest and lowest strengths against plastic deformation, respectively.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2016

Calculation of total and ionization cross sections for electron scattering by primary benzene compounds

The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observations for all the targets reported here, especially for the total cross section.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

New constraint on the Np 237 ( n , γ ) Np 238 integral cross section using the Godiva-IV critical assembly

Accurate knowledge of the 237 Np(n, γ) 238 Np cross section at fast neutron energies is important for applied nuclear science. The presently available experimental data has large disagreements in the fast neutron region. Perform a model-independent measurement of the 237 Np(n, γ) 238 Np integral cross section using a well characterized fast neutron source and compare the result with previous measurements and current nuclear data evaluations. Provide an integral measurement that can be used as a benchmark for current evaluations. Multiple samples of 237 Np were irradiated in the Godiva-IV critical assembly. Following the irradiation, the samples placed in a γ-ray counting setup and the γ-rays emitted from the decay of 238 Np were measured over a time period of approximately 7 days. Multiple γ-ray decay branches of 238 Np were observed. The observed activity of 238 Np was used to calculate the amount of 238 Np produced during the irradiation via the 237 Np(n, γ) 238 Np reaction and an integral cross section of 342(11) mb was measured for the Godiva-IV neutron spectrum. Further, the 238 Np half-life has been measured with a result of 50.31(5) hours. The 237 Np(n, γ) 238 Np integral cross section measured in this work is in agreement with overlapping 1σ error bands to ENDF/B-VIII.0. However, the measured value is 3σ away from the calculated integral cross section using JENDL-5. This measurement offers a reliable benchmark for future 237 Np(n, γ) 238 Np cross section evaluations.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

DOE OSTI2023

Electron collisional excitation cross-section measurements and modeling for select Ni-like to Ge-like gold transitions

We have experimentally determined the electron collisional excitation cross-sections for several 3d→4f and 3d→5f excitations in Ni- to Ge-like Au at energies of ~ 0.4, 1, 2, and 3 keV above threshold energy, E T , for the 3d→4f excitations ( E T ~ 2.5 keV) and ~ 0.2, 1, and 2 keV above threshold energy for the 3d→5f excitations ( E T ~ 3.3 keV). The cross-section measurements are possible by using the GSFC micro-calorimeter to record emission spectra from beam plasmas created in the Livermore EBIT-I electron beam ion trap. The cross-sections are experimentally determined from the ratio of the measured intensities of the collisionally excited lines to the intensities of the radiative recombination lines in monoenergetic electron distribution EBIT-I plasmas. The effects of polarization and Auger processes in the beam plasmas are accounted for in the cross-section determination. Experimentally determined cross-sections are compared with those from HULLAC, DWS, and FAC calculations. Finally, the measurements exhibit significant differences with the calculations of these excitation cross-sections.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2022

Initial study on cross section generation requirements for a PBR equilibrium core

A Serpent model of the HTR-PM equilibrium core was developed for use in cross section prepa-ration studies in order to guide methods development for the Griffin reactor multiphysics applica-tion. The model includes detailed isotopics for 10 distinct pebble burnup groups in 126 core zoneswith unique fuel and moderator temperatures obtained from a coupled neutronics-thermal-fluidsequilibrium core calculation using Griffin-Pronghorn. A sensitivity study of the fuel and mod-erator temperatures for various core regions was performed with the MOOSE stochastic tools.The results show that the uncertainties are, not unexpectedly, dominated by the value of the fluidtemperature and that the power level, heat transfer coefficient and effective conduction to neigh-boring pebbles and fluid constitute, at best, second order effects. The temperature uncertaintyrange varies from 28 K to 57 K at the core entry and exit planes, respectively, but these val-ues are probably higher. We still have to quantify the significance of these uncertainties in thepreparation of cross sections, which will be postponed for future work. In addition, we verifythat the single effective pebble approach works well for the preparation of region averaged crosssections in the infinite domain approximation. Nevertheless, there are significant discrepanciesin the cross sections when compared to the multi-pebble model. This could affect the predictionof peak values and in the depletion calculation. We conclude that is highly desirable for futurestudies with Griffin to be able to handle both the ?effective? pebble approximation and the multi-pebble approach for the various pebble burnup groups. This enables Griffin users the flexibilityto perform higher-fidelity studies. Finally, we initiate the preparation of cross sections for variouscore regions from the full core Serpent reference model. We quantify the differences in 26 groupcross sections from infinite domain models. These reference cross sections will serve to validatethe double heterogeneity, self-shielding, and spectrum-correction methods in Griffin.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2016

On-the-Fly Treatment of Temperature Dependent Cross Sections in the Unresolved Resonance Regions in RMC Code

Monte Carlo method can provide high fidelity neutronics analysis of different nuclear reactors, owing to its advantages of the flexible geometry modeling and the use of continuous-energy nuclear cross sections. It can also be coupled with thermal-hydraulics codes to consider the feedback. For thermal reactors such as PWR and HTGR, two main temperature effects should be considered. The first is the effect of thermal motion of target nuclei in resolved resonance energy regions, which is known as Doppler effect. The second is the thermal scattering and bound effect in thermal energy regions. The traditional approach of pre-generated cross sections has difficulty in memory footprint for detailed temperature modelling in multi-physics calculations. Recently, on-the-fly (OTF) technique has been proposed in order to reduce the memory consumption for both resolved resonance energy and thermal energy. For fast reactors calculations, the temperature dependence of cross sections in the unresolved resonance energy regions is also important. However, less attention was paid to the unresolved resonance regions compared with resolved resonance energy and thermal energy. In this paper, the on-the-fly temperature treatment of cross sections in unresolved resonance regions was proposed and developed in RMC codes. The results show that the on-the-fly treatment has high efficiency and satisfactory fidelity. The on-the-fly treatment of unresolved resonance region was also combined with the target motion sampling (TMS) method for resolved resonance energy. The formats of libraries were changed, in which the probability tables were separated from the cross sections. Then the interpolation of probability table was performed on-the-fly during the transport routine. The results show that the on-the-fly treatment has high efficiency and satisfactory fidelity. The on-the-fly treatment of unresolved resonance region was also combined with the target motion sampling (TMS) method for resolved resonance energy, showing that TMS method is effective and accurate for cross sections treatment in resolved resonance energy regions. The memory saving of the on-the-fly treatment is also considerable. For the high-fidelity 'transport-burnup-thermal-hydraulics' coupling calculation, the memory requirement is 60 Mb. (authors)

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗