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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
NASA NTRS1965

Heats of mixing in praseodymium-neodymium solid solutions.

The heats of solution in liquid tin of pure praseodymium, pure neodymium and nine praseodymium-neodymium binary alloys have been measured using liquid metal solution calorimetry. A plot of the measured heat effect for the alloys as a function of composition is linear, with the terminal points being the measured values for the pure components. This linear dependency indicates that the heat of mixing in the binary praseodymium-neodymium system is zero within experimental error, and therefore the binary alloys obey one of the criteria for an ideal solution.

Calorimetry↗
NASA NTRS1980

Neodymium YAG lasers. Citations from the International Aerospace Abstracts data base

Various aspects of neodymium yag lasers are discussed in approximately 267 citations. Laser materials and outputs, laser mode locking; crystal, fiber, and nonlinear optics, optical pumping communications, energy conversion efficiency, and laser applications are covered. Pulsed, continuous wave, solid state, Q switched, infrared, and dye lasers are included.

Mauk, S. C.↗
NASA NTRS1984

Analysis of a 10 megawatt space-based solar-pumped neodymium laser system

A ten megawatt solar-pumped continuous liquid laser system for space applications is examined. It is found that a single inflatable mirror of 434 m diameter used in conjunction with a conical secondary concentrator is sufficient to side pump a liquid neodymium lasant in an annular tube of 6 m length and 1 m outer and 0.8 m inner diameter. About one fourth of intercepted radiation converging on the laser tube is absorbed and one fifth of this radiation is effective in populating the upper levels. The liquid lasant is flowed through the annular laser cavity at 1.9 m/s and is cooled via a heat exchanger and a large radiator surface comparable in size to the concentrating mirror. The power density of incident light within the lasant of approximately 68 watt/cu cm required for cw operation is exceeded in the present annular configuration. Total system weight corresponds to 20,500 kg and is thus capable of being transported to near Earth orbit by a single shuttle flight.

Kurweg, U. H.↗
NASA NTRS1985

Highly efficient neodymium:yttrium aluminum garnet laser end pumped by a semiconductor laser array

In recent experiments, 80-mW CW power in a single mode has been achieved from a neodymium:yttrium aluminum garnet (Nd:YAG) laser with only 1 W of electrical power input to a single semiconductor laser array pump. This corresponds to an overall efficiency of 8 percent, the highest reported CW efficiency for a Nd:YAG laser. A tightly focused semiconductor laser end pump configuration is used to achieve high pumping intensities (on the order of 1 kW/sq cm), which in turn causes the photon to photon conversion efficiency to approach the quantum efficiency (76 percent for Nd:YAG at 1.06 microns pumped at 0.810 micron). This is achieved despite the dual-lobed nature of the pump. Through the use of simple beam-combining schemes (e.g., polarization coupling and multireflection point pumping), output powers over 1 W and overall electrical to optical efficiencies as high as 10 percent are expected.

Sipes, D. L.↗
NASA NTRS1989

Neodymium and lead isotope evidence for enriched early Archean crust in North America

Neodymium and lead isotope measurements and uranium-lead zircon geochronology from Archaean gneisses of the Slave Province in the Northwest Territories of Canada are reported. The gneisses contain zircons with cores older than 3.842 Gyr and an epsilon(Nd) (3.7 Gyr) of - 4.8. This is the oldest reported chondritic model age for a terrestrial sample and provides evidence for strongly enriched pre-3.8-Gyr crust, a reservoir complementary to the depleted mantle already in existence by 3.8 Gyr before the present.

Bowring, Samuel A.↗
NASA NTRS1991

Power scaling of diode-pumped neodymium yttrium aluminum borate laser

Preliminary results are presented of the efficient diode-pumped operation of a neodymium yttrium aluminum borate (NYAB) laser at 531.5 nm using two 1-W diode-laser arrays for the pump. With 1380 mW of CW power incident on the crystal, as much as 51 mW of 532.5-nm laser radiation was obtained with the unoptimized cavity. The corresponding optical-to-optical conversion efficiency was 3.7 percent. A plot of the output 531.5 nm vs incident 807 nm pump power is shown. The crystal output power was critically dependent on the rotational and translational adjustment of the NYAB crystal inside the cavity. It is suggested that a crystal cut at the exact phase matching angle, placed in a cavity with proper optimal reflection and transmission mirror coatings, and pumped at proper wavelength can result in higher output power. Thus, the NYAB output power approaches that of a CW intracavity frequency doubled Nd:YAG laser.

Hemmati, Hamid↗
NASA NTRS1994

Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body

Neodymium, stontium, and chromium isotopic studies of the LEW86010 angrite established its absolute age and the formation interval between its crystallization and condensation of Allende CAIs from the solar nebula. Pyroxene and phosphate were found to contain approximately 8% of its Sm and Nd inventory. A conventional Sm-147-Nd-143 isochron yielded an age of 4.53 +/- 0.04 Ga (2 sigma and Epsilon(sub Nd sup 143)) = 0.45 +/- 1.1. An Sm-146-Nd-142 isochron gives initial Sm-146/Sm-144 = 0.0076 +/- 0.0009 and Epsilon (sub Nd sup 142) = -2.5 +/- 0.4. The Rb-Sr analyses give initial Sr-87/Sr-86 Iota(sub Sr sup 87) = 0.698972 +/- 8 and 0.698970 +/- 18 for LEW and ADOR, respectively, relative to Sr-87/Sr-86 = 0.71025 for NBS987. The difference, Delta Iota(sub Sr Sup 87), between Iota (sub sr sup 87) for the angrites and literature values for Allende CAIs, corresponds to approximately Ma of growth in a solar nebula with a CI chondrite value of Rb-87/Sr-86 = 0.91, or approximately 5 Ma in a nebula with solar photospheric Rb-87/Sr-86 = 1.51. Excess Cr-53 from extinct Mn-53(t(sub 1/2) = 3.7 Ma)in LEW86010 corresponds to initial Mn-53/Mn-55 = 4.4 +/- 1.0 x 10(exp -5) for the inclusions as previously reported by the Paris group (Birck and Allegre, 1988). The Sm-146/Sm-144 value found for LEW86010 corresponds to solar system initial (Sm-146/Sm-144) = 0.0080 +/- 0.0009 for crystallization 8 Ma after Allende, the difference between Pb-Pb ages of angrites and Allende, or 0.0086 +/- 0.0009 for crystallation 18 Ma after Allende, using the Mn-Cr formation interval. The isotopic data are discussed in the context of a model in which an undifferentiated 'chondritic' parent body formed from the solar nebula approximately Ma after Allende CAIs and subsequently underwent differentiation accompanied by loss of volatiles. Parent bodies with Rb/Sr similar to that of CI, CM, or CO chondrites could satisfy the Cr and Sr isotopic systematics. If the angrite parent body had Rb/Sr similar to that of CV meteorites, it would have to form slightly later, approximately 2.6 Ma after the CAIs, to satisfy the Sr and CR isotopic systematics.

Nyquist, L. E.↗
NASA NTRS2007

Recent Progress in the Development of Neodymium Doped Ceramic Yttria

Solid-state lasers play a significant role in providing the technology necessary for active remote sensing of the atmosphere. Neodymium doped yttria (Nd:Y2O3) is considered to be an attractive material due to its possible lasing wavelengths of aprrox.914 nm and approx.946 nm for ozone profiling. These wavelengths when frequency tripled can generate UV light at approx.305 nm and approx.315 nm, which is particularly useful for ozone sensing using differential absorption lidar technique. For practical realization of space based UV transmitter technology, ceramic Nd:Y2O3 material is considered to possess great potential. A plasma melting and quenching method has been developed to produce Nd3+ doped powders for consolidation into Nd:Y2O3 ceramic laser materials. This far-from-equilibrium processing methodology allows higher levels of rare earth doping than can be achieved by equilibrium methods. The method comprises of two main steps: (a) plasma melting and quenching to generate dense, and homogeneous doped metastable powders, (b) pressure assisted consolidation of these powders by hot isostatic pressing to make dense nanocomposite ceramics. Using this process, several 1" x 1" ceramic cylinders have been produced. The infrared transmission of undoped Y2O3 ceramics was as high as approx.75% without anti-reflection coating. In the case of Nd:Y2O3 ceramics infrared transmission values of approx.50% were achieved. Furthermore, Nd:Y2O3 samples with dopant concentrations of up to approx.2 at. % were prepared without significant emission quenching.

Prasad, Narasimha S.↗
NASA NTRS2018

Probing Neodymium Isotopic Variations in the Inner Solar System

One of the key problems in planetary science is the identification of the building blocks of Earth, and whether they exist within our current collection of meteorites. Stable mass independent isotopic anomalies, usually nucleosynthetic in origin, are a key tool in fingerprinting material coming from different accretionary regions within the protoplanetary disk. For a number of isotopic systems such as O, Ni, Ti and Cr, enstatite chondrites (EC) appear to be the strongest candidates for Earth's building blocks, despite their low Mg/Si ratios relative to the bulk Earth. It has been proposed that Earth, the Moon-forming impactor and enstatite chondrites all were originally sourced from the same reservoir in the protoplanetary disk, but subsequently experienced divergent chemical evolution pathways. This was recently challenged by who used the correlation between Mo and Nd isotopes in bulk meteorites to argue that such a reservoir does not exist as the isotopic composition of enstatite chondrites is resolvable from Earth. However, in detail the Nd isotopic ratios of EC ((142)Nd/(144)Nd, (148)Nd/(144)Nd, (150)Nd/(144)Nd) show considerable variability, and overlap significantly with the isotopic composition of both the bulk Earth and ordinary chondrites (OC). previously identified Nd isotopic variability in EC, linking it to the degree of equilibration the meteorite had experienced, however they only focused on collecting high precision (142)Nd/(144)Nd, which also has contributions from the decay of the short-lived Sm-146 nuclide (t(sub 1/2) ~103 Myr), making identification of nucleosynthetic anomalies less clear. While the study of reports all the Nd isotopic ratios measured at high precision, only equilibrated EC were analyzed. Therefore, with the currently published data it is unclear to what extent thermal equilibration in the EC is responsible for the variation observed in the stable Nd isotopic ratios, and whether the EC reservoir can be resolved from Earth. In order to better understand the genetic relationship between enstatite chondrites and the Earth we are carrying out a more systematic study including both equilibrated and unequilibrated enstatite chondrites, focusing on high precision analysis of all the stable Nd isotopic ratios.

SOLAR SYSTEM↗
NASA NTRS1978

Barium and neodymium isotopic anomalies in the Allende meteorite

The discovery of Ba and Nd isotopic anomalies in two inclusions from the Allende meteorite is reported. The inclusions are Ca-Al-rich objects typical of the type considered as high-temperature condensation products in the solar nebula and contain distinctive Mg and O isotopic anomalies of the FUN (mass Fractionation, Unknown Nuclear processes) type. Mass-spectrometry results are discussed which show that inclusion C1 has anomalies in Ba at masses 134 and 136, while inclusion EK1-4-1 exhibits large marked negative anomalies at 130, 132, 134, and 136, as well as a positive anomaly at 137. It is also found that inclusion EK1-4-1 shows marked negative anomalies in Nd at masses 142, 146, 148, and 150, in addition to a positive anomaly at 145. These isotopic shifts are attributed to addition of r-process nuclei rather than mass fractionation. It is suggested that an onion-shell supernova explosion followed by injection into the solar nebula is the most likely generic model that may explain the observations.

Mcculloch, M. T.↗