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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Using real-time nuclear activation detectors for measuring neutron yields from D(D, T)n reactions on the national ignition facility (NIF)

The National Ignition Facility (NIF) has 48 Real-Time Nuclear Activation Detectors distributed around the target chamber capable of measuring deuterium-triton reaction neutron yields with high precision. Here, in this work, we extend this functionality to deuterium–deuterium (DD) reaction neutrons using a nuclear reaction that occurs in the detector’s scintillator material. The corresponding decay of the activated material has a very short half-life of 5 s, which necessitates rapid data collection immediately following an experiment. In this regime, dead time can be very high (>50%) adding significant uncertainty to the measurement. To combat this, we have developed a dead time model that can self-consistently describe the measured data. Initial results show reasonable agreement (within 20%) with DD neutron yields from neutron time-of-flight spectrometers.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Magnetic excitations in the double-perovskite iridates La 2 M IrO 6 ( M = Co , Ni , and Zn ) mediated by 3 d – 5 d hybridization

By performing resonant inelastic x-ray scattering (RIXS) measurements at the Ir L 3 edge, we have investigated the low-energy elementary excitations in a series of double-perovskite iridate single crystals, La 2 MIrO 6 (M=Co,Ni,and Zn). Almost dispersionless magnetic excitations at ~42(6) meV and ~35(5) meV have been observed in crystals containing magnetic 3d ions, La 2 CoIrO 6 and La 2 NiIrO 6 , respectively. In contrast, this low-energy magnetic excitation is absent in La 2 ZnIrO 6 in which the 3d ions are nonmagnetic, suggesting the importance of 3d–5d hybridization in the magnetic properties of these double-perovskite iridates. Furthermore, the magnetic excitation is suppressed completely above the magnetic ordering temperature, suggesting the inadequacy of using a simple spin Hamiltonian to describe magnetism of these materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Elastic differential cross-section ${\mathrm{d}}\sigma /{\mathrm{d}}t$ at $\sqrt{s}=2.76\hbox {TeV}$ and implications on the existence of a colourless C-odd three-gluon compound state

The proton-proton elastic differential cross section dσ/dt has been measured by the TOTEM experiment at √ s = 2.76 TeV energy with β* = 11 m beam optics. The Roman Pots were inserted to 13 times the transverse beam size from the beam, which allowed to measure the differential cross-section of elastic scattering in a range of the squared four-momentum transfer (|t|) from 0.36 GeV 2 to 0.74 GeV 2 . The differential cross-section can be described with an exponential in the |t|-range between 0.36 and 0.54 GeV 2 , followed by a diffractive minimum (dip) at |t dip | = (0.61 ± 0.03) GeV 2 and a subsequent maximum (bump). The ratio of the dσ/dt at the bump and at the dip is 1.7±0.2. When compared to the proton–antiproton measurement of the D0 experiment at √ s = 1.96 TeV, a significant difference can be observed. Under the condition that the effects due to the energy difference between TOTEM and D0 can be neglected, the result provides evidence for a colourless C-odd three-gluon bound state exchange in the t-channel of the proton-proton and proton–antiproton elastic scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1983

NASA-JSC measurements during la campagne d'intercomparaison d'ozonometres, Gap, France, June 1981

Measurements made by the NASA-JSC ozone instrument during the ozone intercomparison campaign from Gap, France during June 1981 are reported. Two flights were made on board the large balloon platform with other instruments using different techniques. The NASA-JSC instrument employs UV absorption photometry to obtain in situ results. Concentration and mixing ratio profiles are given for altitudes from 16 km to float altitudes of 32 and 39 km, respectively, for the two flights. A measure of the total column content of ozone was obtained by integrating the NASA-JSC results from 16 km to float altitude and combining them with results from other techniques below 16 km and above float altitudes.

Robbins, D. E.↗
NASA NTRS1989

Comparison of full 3-D, thin-film 3-D, and thin-film plate analyses of a postbuckled embedded delamination

Local buckling can cause large interlaminar stresses along the delamination front, which can lead to delamination growth. This paper examines several methods of calculating strain-energy release rates, which are often used to predict delamination growth. The thin-film plate analysis, which was least expensive, calculated the total strain-energy release rate G(T) quite accurately. However, the stress field along the delamination front is highly mixed-mode and has no fixed ratio of G(I) to G(II). Since plate analysis can only calculate G(T), it would not be useful for accurate predictions of delamination growth if mode mix is important.

Whitcomb, John D.↗
NASA NTRS1990

2-D to 3-D global/local finite element analysis of cross-ply composite laminates

An example of two-dimensional to three-dimensional global/local finite element analysis of a laminated composite plate with a hole is presented. The 'zoom' technique of global/local analysis is used, where displacements of the global/local interface from the two-dimensional global model are applied to the edges of the three-dimensional local model. Three different hole diameters, one, three, and six inches, are considered in order to compare the effect of hole size on the three-dimensional stress state around the hole. In addition, three different stacking sequences are analyzed for the six inch hole case in order to study the effect of stacking sequence. The existence of a 'critical' hole size, where the interlaminar stresses are maximum, is indicated. Dispersion of plies at the same angle, as opposed to clustering, is found to reduce the magnitude of some interlaminar stress components and increase others.

Thompson, D. Muheim↗