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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

2D coherence imaging measurements of C 2+ ion temperatures in the divertor of Wendelstein 7-X

For the first time, 2D ion temperature values are derived from coherence imaging spectroscopy (CIS) fringe contrast measurements by taking Zeeman line broadening effects into account during the analysis procedure of a spatial-heterodyne CIS instrument. This allowed 2D images of C 2+ ion temperatures (T i ) across the 3D-shaped island divertor of the Wendelstein 7-X stellarator. Ion temperatures ranging from 10 to 20 eV are observed for the C 2+ impurity species in the region above the divertor targets. During the transition from the attached to the detached plasma state, the C 2+ radiation zone moves from close to the divertor target towards the last closed flux surface. Within this radiation zone, C 2+ temperature does not decrease significantly. Experimentally, the coherence imaging measurements were cross-calibrated at one poloidal cross-section using a high resolution Echelle spectrometer, that shared its sightlines with the coherence imaging diagnostic. The spectra demonstrated that, apart from Doppler broadening, the Zeeman effect significantly contributes to the spectral line broadening and cannot be neglected when analyzing the CIS contrast data for T i extraction in the edge and scrape-off-layer of Wendelstein 7-X (W7-X), due to the relatively low temperatures (T i < 100 eV) and high magnetic fields (B ≈ 2.5 T).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Quadrupole and octupole collectivity in 143 Ba

The neutron-rich barium nuclei have been the subject of intense interest due to the enhanced octupole correlations they are predicted to exhibit. The observation of enhanced octupole collectivity in 144,146 Ba as measured in sub-barrier Coulomb excitation, consistent with static octupole deformation, has further heightened this interest. In the present work, these studies are extended to the neighboring odd-mass 143 Ba to investigate the interplay between single-particle and collective octupole degrees of freedom. A new measurement of the first 9/2 – -state lifetime is also presented. Reflection-Asymmetric Triaxial Particle Rotor Model calculations indicate that the negative-parity bands in 143 Ba can be understood as a decoupled structure of νh 9/2 parentage, while the positiveparity bands are built on a decoupled octupole phonon. Here, no evidence for E3 excitation is observed in this work, but an upper limit is placed on the E3 matrix element to the lowest octupole band.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Nuclear states projected from a pair condensate

Atomic nuclei exhibit deformation, pairing correlations, and rotational symmetries. To meet these competing demands in a computationally tractable formalism, we revisit the use of general pair condensates with good particle number as a trial wave function for even-even nuclei. After minimizing the energy of the condensate, allowing for general triaxial deformations, we project out states with good angular momentum with a fast projection technique. To show applicability, we present example calculations from pair condensates in several model spaces and compare against angular-momentum projected Hartree-Fock and full configuration-interaction shell-model calculations. This approach successfully generates spherical, vibrational, and rotational spectra, demonstrating potential for modeling medium- to heavy-mass nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Quantum Computation of Dynamical Quantum Phase Transitions and Entanglement Tomography in a Lattice Gauge Theory

Strongly coupled gauge theories far from equilibrium may exhibit unique features that could illuminate the physics of the early universe and of hadron and ion colliders. Studying real-time phenomena has proven challenging with classical-simulation methods but is a natural application of quantum simulation. To demonstrate this prospect, we quantum compute nonequal-time correlation functions and perform entanglement tomography of nonequilibrium states of a simple lattice gauge theory, the Schwinger model, using a trapped-ion quantum computer by IonQ Inc. As an ideal target for near-term devices, a recently predicted dynamical quantum phase transition in this model is studied by preparing, quenching, and tracking the subsequent nonequilibrium dynamics in three ways: (i) overlap echos signaling dynamical transitions, (ii) nonequal-time correlation functions with an underlying topological nature, and (iii) the entanglement structure of nonequilibrium states, including entanglement Hamiltonians. These results constitute the first observation of a dynamical quantum phase transition in a lattice gauge theory on a quantum computer and are a first step toward investigating topological phenomena in nuclear and high-energy physics using quantum technologies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Single-shot imaging with randomized structured illumination at a free electron laser

Stroboscopic nanoscale imaging with free electron laser light is revolutionizing our understanding of fast dynamics in heterogeneous systems. The short wavelength of X-ray and extreme ultraviolet radiation makes it possible to achieve nanoscale resolution, while resonance with atomic transitions gives access to electronic and magnetic degrees of freedom. Here, we report on our implementation of a recently developed imaging method, randomized probe imaging, at a free electron laser. The advantage of randomized probe imaging over existing methods is its compatibility with extended and strongly scattering samples. Our implementation delivers robust single-shot reconstructions at up to a full-pitch resolution of 400 nm over a field of view with a 40 µm diameter. We also demonstrate single-shot imaging of magnetic domain structures using circular dichroism at resonance, paving the way to future time-resolved studies of magnetic dynamics, shock physics, and the dynamics of collective electronic phases.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Indications of flat bands driving the δ to α volume collapse of plutonium

On cooling from the melt, plutonium (Pu) undergoes a series of structural transformations accompanied by a ≈ 28% reduction in volume from its δ phase to its α phase at low temperatures. While Pu’s partially filled 5f -electron shells are known to be involved, their precise role in the transformations has remained unclear. By using calorimetry measurements on α-Pu and gallium-stabilized δ-Pu combined with resonant ultrasound and X-ray scattering data to account for the anomalously large softening of the lattice with temperature, we show here that the difference in electronic entropy between the α and δ phases dominates over the difference in phonon entropy. Rather than finding an electronic specific heat characteristic of broad $f$-electron bands in α-Pu, as might be expected to occur within a Kondo collapsed phase in analogy with cerium, we find it to be indicative of flatter subbands. An important role played by Pu’s 5$f$ electrons in the formation of its larger unit cell α phase comprising inequivalent lattice sites and varying bond lengths is therefore suggested.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

The Hubble Space Telescope PanCET Program: An Optical to Infrared Transmission Spectrum of HAT-P-32Ab

We present a 0.3−5 μm transmission spectrum of the hot Jupiter HAT-P-32Ab observed with the Space Telescope Imaging Spectrograph and Wide Field Camera 3 instruments mounted on the Hubble Space Telescope, combined with Spitzer Infrared Array Camera photometry. The spectrum is composed of 51 spectrophotometric bins with widths ranging between 150 and 400 Å, measured to a median precision of 215 ppm. Comparisons of the observed transmission spectrum to a grid of 1D radiative-convective equilibrium models indicate the presence of clouds/hazes, consistent with previous transit observations and secondary eclipse measurements. To provide more robust constraints on the planet’s atmospheric properties, we perform the first full optical to infrared retrieval analysis for this planet. The retrieved spectrum is consistent with a limb temperature of 1248{sub −92}{sup +92} K, a thick cloud deck, enhanced Rayleigh scattering, and ∼10× solar H{sub 2}O abundance. We find log(Z/Z {sub ⊙}) = 2.41{sub −0.07}{sup +0.06}, and compare this measurement with the mass–metallicity relation derived for the solar system.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

The 1.4-2.7 micron spectrum of the point source at the galactic center

The spectrum of the 2-micron point source at the galactic center is presented over the range from 1.4 to 2.7 microns. The two-level-transition CO band heads are seen near 2.3 microns, confirming that the radiation from this source is due to a cool supergiant star. The heliocentric radial velocity is found to be - 173 (+ or -90) km/s and is consistent with the star being in orbit about a dense galactic nucleus. No evidence is found for Brackett-gamma emission, and no interstellar absorption features are seen. Upper limits for the column densities of interstellar H2, CH4, CO, and NH3 are derived.

Treffers, R. R.↗
NASA NTRS1984

Molecular astronomy at submillimeter wavelengths

It is pointed out that the region of the spectrum from 300 to 3000 GHz (100 to 1000 microns), which is referred to as the submillimeter, is one of the least explored areas in the electromagnetic spectrum. The reasons for this situation are related to a lack of adequate instrumentation for detecting the radiation and an almost complete absorption of the radiation by the earth's atmosphere. The vast majority of the rotational transitions of molecules occur in the millimeter and submillimeter wavelength region of the spectrum. The strength of the lines increases at higher frequencies until a condition is reached in which the energy levels are no longer populated. The study of molecular clouds at submillimeter wavelengths promises to provide new important results. Attention is given to the design of suitable submillimeter receivers, problems of atmospheric transmission, and galactic molecular lines.

Buhl, D.↗
NASA NTRS1986

The Orbital Acceleration Research Experiment

The hardware and software of NASA's proposed Orbital Acceleration Research Experiment (OARE) are described. The OARE is to provide aerodynamic acceleration measurements along the Orbiter's principal axis in the free-molecular flow-flight regime at orbital attitude and in the transition regime during reentry. Models considering the effects of electromagnetic effects, solar radiation pressure, orbiter mass attraction, gravity gradient, orbital centripetal acceleration, out-of-orbital-plane effects, orbiter angular velocity, structural noise, mass expulsion signal sources, crew motion, and bias on acceleration are examined. The experiment contains an electrostatically balanced cylindrical proofmass accelerometer sensor with three orthogonal sensing axis outputs. The components and functions of the experimental calibration system and signal processor and control subsystem are analyzed. The development of the OARE software is discussed. The experimental equipment will be enclosed in a cover assembly that will be mounted in the Orbiter close to the center of gravity.

Blanchard, R. C.↗
NASA NTRS1986

Detection of OH from Comet Halley in the far-infrared

The 2 Pi 3/2 (J = 5/2 yields 3/2 + yields - parity) transition of OH was detected in comet Halley at 119.44 microns. The upper limit to the line intensity of the - yields + parity transition is 119.23 microns. The ratio of these lines is consistent with radiative pumping of the rotational levels through absorption of near ultraviolet solar photons which excite the low lying vibrational levels of OH. The far-infrared lines probe the inner regions of the coma where OH is produced through photodissociation of a parent molecule (presumably H2O). Hence, these lines complement the 18 cm radio measurements which are sensitive to the outer regions of the comet coma. The OH production rate is highly model dependent but is of the order 2 to 4 times 10 to the 29th power molecules/sec.

Stacey, Gordon J.↗
NASA NTRS1990

Intersubband absorption in Si(1-x)Ge(x/Si superlattices for long wavelength infrared detectors

Researchers calculated the absorption strengths for intersubband transitions in n-type Si(1-x)Ge(x)/Si superlattices. These transitions can be used for the detection of long-wavelength infrared radiation. A significant advantage in Si(1-x)Ge(x)/Si supperlattice detectors is the ability to detect normally incident light; in Ga(1-x)Al(x)As/GaAs superlattices, intersubband absorption is possible only if the incident light contains a polarization component in the growth direction of the superlattice. Researchers present detailed calculation of absorption coefficients, and peak absorption wavelengths for (100), (111) and (110) Si(1-x)Ge(x)/Si superlattices. Peak absorption strengths of about 2000 to 6000 cm(exp -1) were obtained for typical sheet doping concentrations (approx. equals 10(exp 12)cm(exp -2)). Absorption comparable to that in Ga(1-x)Al(x)As/GaAs superlattice detectors, compatibility with existing Si technology, and the ability to detect normally incident light make these devices promising for future applications.

Rajakarunanayake, Yasantha↗
NASA NTRS1990

Study of a cesium plasma as a selective emitter for thermophotovoltaic applications

This experimental study evaluates the potential of a cesium plasma as an emitter for a thermophotovoltaic (TPV) energy conversion system. A cesium plasma, as a result of the ground-state transitions of its single outer-shell electron, produces large amounts of radiation in the 850-890-nm wavelength region. This would provide excellent coupling to silicon, gallium arsenide, and indium phosphide photovoltaic cells. Measurements of the radiative efficiency, the sum of the power at the 852 and 894 nm wavelengths relative to the total emitted power, were made and correlated to the plasma operating variables. It was determined that, for atomic density in the range (3-6) x 10 exp 21/cu cm and electron temperature in the range 2000-3000 K, radiative efficiencies in excess of 70 percent are attainable. This would indicate that a cesium plasma with its selective emission characteristics and low electron operating temperatures of 2000-3000 K would be an excellent candidate as an emitter in a TPV system.

Lowe, R.↗
NASA NTRS1992

Observations of a new SAGE II aerosol extinction mode following the eruption of Mt. Pinatubo

In the aftermath of the eruption of Mt. Pinatubo, multiwavelength stratospheric aerosol extinction measurements by the satellite-borne Stratospheric Aerosol and Gas Experiment (SAGE II) revealed the presence of a previously unobserved mode of aerosol that exhibited high extinction but a small inferred particle size. This mode may represent a transitional phase between the very small aerosol created by gas-to-particle conversion and a quasi-steady state, post-volcanic aerosol that exhibits both large extinction and large particle size. The presence of a transitional small aerosol mode may have a significant impact on chemical and radiative processes in the stratosphere.

Thomason, Larry W.↗
NASA NTRS1997

The Effectiveness of the Proportional Counter With a Specially Designed Filter as a Solar X-Ray Monitor on the NEAR Mission

The X-ray instrument package on the Near Earth Asteroid Rendezvous (NEAR) spacecraft is designed to provide direct measurements of the major elemental abundances for the asteroid 433 Eros. These will be the first such measurements ever made for a 'primitive' body. For this task to be performed, simultaneous measurements must be provided of both the X-ray lines characteristic of major elements at the asteroid's surface as well as the solar flux, which is the source of these lines (1,2). The solar flux consists of a continuum which is generated by thermal bremstrahlung and radiative recombination, with superimposed major lines which result from emission due to transitions in H and He-like ions. The relative contribution of each component of the solar flux varies as the level of solar output changes, and thus solar output must be monitored to correct for varations in surface data caused by the changing levels of solar output.

Clark, P. E.↗