SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The xenon anomalies trapped in meteorites and the moon may have first been trapped in circumstellar grains formed in or outside of postexplosive stars. In that case, the initial solar nebula need not have contained most of their radioactive progenitors, and this would necessitate major revision of the history of solar system formation.
The process of trapped particle absorption by the inner Jovian satellites is considered in detail taking into account both the particle and satellite motions in a magnetic dipole field which is displaced from the center of the planet and tilted with respect to the planetary rotation axis. An expression is derived for computing the sweeping time at a given satellite, defined as the time required for the satellite to sweep up a given fraction of the trapped particles within its sweeping region. By making use of the sweeping time and the radial diffusion equation of particle transport approximate expressions for the diffusion coefficient are derived. Measurements obtained by Pioneer 10 are then used to obtain estimates of the diffusion coefficient at the orbits of Io and Europa. We find that the diffusion coefficient is a function of energy and magnetic latitude for electrons in the energy range 0.7-14 MeV.
It was previously shown that trapped electron fluxes of energies in the range from 50 keV to 1 MeV observed in the afternoon magnetosphere during substorms frequently undergo periodic variations. High-resolution electron spectrometer data indicate that these electron variations are periodic in the range of about 2-12 min, correlated with magnetic field variations, organized by the local magnetic field, and dependent on pitch angle. The observations suggest that the electron variations are adiabatic. The study derives quantitative adiabatic expressions of particle flux variations in a model geomagnetic field perturbation to show that the observational features are consistent with effects arising from adiabatic modulation of trapped particle fluxes.
A pressure vessel is described that can be closed by a single translational motion within 1 sec. The vessel is a key component of a trap for small marine animals and operates automatically on the sea floor. As the vessel descends to the sea floor, it is subjected both internally and externally to the high pressures of the deep sea. The mechanism for closing the pressure vessel on the sea floor is activated by the timed release of the ballast which was used to sink the trap. As it rises to the sea surface, the internal pressure of the vessel remains near the value present on the sea floor. The pressure vessel has been used in simulated ocean deployments and in the deep ocean (9500 m) with a 75%-85% retention of the deep-sea pressure. Nearly 100% retention of pressure can be achieved by using an accumulator filled with a gas.
System for controlled injection of electrons or holes into oxide layer of MOS capacitor can be used to measure oxide trapping parameters. Since trapping mechanisms can cause degradation and ultimate failure of MOS elements exposed to ionizing radiation, system can be helpful in predicting device tolerance.
Results are presented of rare-gas analyses of 10084 ilmenite samples which have been etched to depths of about 1 micrometer in an attempt to remove the surface layer of trapped solar-wind gases, thereby allowing detection of the more deeply implanted solar-flare ions in the remaining trapped gases. A tendency found for the Ne-20/Ne-22 ratios in the etched ilmenite to reflect the solar-wind ratio measured in the solar-wind composition experiment foils may represent a cancellation of mass-fractionation effects. The Ne-20/Ne-22 ratio in the saturated layer is lowered with respect to the solar wind by preferential diffusive loss, but is raised again in the gas diffusing inward by the same preferential mobilization of Ne-20 relative to Ne-22. Attention is also given to the significance of the findings in the case of argon, krypton, and xenon.
A one-dimensional chain of ions or molecules and electrons described by a Froehlich-type Hamiltonian with quartic phonon anharmonicities is investigated. It is shown that the anharmonic lattice supports supersonic solitons which under favorable circumstances may trap electrons and transport them along the lattice. For a lattice constant/soliton spatial extent quotient of the order of 0.1, rough estimates give electron trapping energies in the meV range. They imply a useful temperature range, up to tens of degrees K, for observing the new effect. The activation energy of a lattice soliton is proportional to the molecular mass and is therefore quite high (about 1 eV) for typical quasi-one-dimensional organic systems.
Singly ionized mercury atoms have a structure similar to neutral alkali atoms. They can be maintained as ions for very long times in an RF quadrupole ion trap. Thus, their ground state hyperfine structure can be used to make a frequency standard using optical pumping techniques similar to the well-known rubidium standard. The mass 199 isotope of mercury has an ionic hyperfine structure of 40.5 GHz. In a trap system a linewidth of 10 Hz has been measured. An expression is presented for the short-term stability of a proposed mercury standard as set by the achieved signal to noise ratio. There is prospect of further improvement. Long-term stability is affected by second order doppler effect, and by pressure, light, and Stark shifts. However, these appear either sufficiently small or sufficiently controlable that the proposed mercury ion standard would be competitive with existing standards.
An apparatus is described in which hydrogen atoms were trapped at temperatures down to 1.1 K in the 11 T field of a large volume superconducting magnet. A high sensitivity thermal detector was used to study trapping and recombination of atoms on the detector surface. The apparatus permits the application of extremely high steady state magnetic fields to study the potential effects of electron spin polarization on the stabilization of hydrogen atoms.
A neutron-irradiated bulk sample of the Murray (C-2) carbonaceous chondrite was etched with H2O2 and then divided into colloidal and non-colloidal fractions. The H2O2 treatment removed about 80% of the trapped Xe and greatly increased variations in the Xe-129/Xe-132 ratio measured in stepwise heating. The colloid showed very little excess Xe-129, but the anti-colloid gave a fairly good I-Xe correlation corresponding to formation 3.7 + or - 2.1 m.y. after Bjurbole. Variations in the trapped Xe component were also observed; most notably the 550 C anti-colloid fraction has large deficiencies relative to AVCC at the heavy isotopes.
Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas.
The Timeline Resource Analysis Program (TRAP), developed for scheduling and timelining problems, is described. Given an activity network, TRAP generates timeline plots, resource histograms, and tabular summaries of the network, schedules, and resource levels. It is written in ANSI FORTRAN for the Honeywell SIGMA 5 computer and operates in the interactive mode using the TEKTRONIX 4014-1 graphics terminal. The input network file may be a standard SIGMA 5 file or one generated using the Interactive Graphics Design System. The timeline plots can be displayed in two orderings: according to the sequence in which the tasks were read on input, and a waterfall sequence in which the tasks are ordered by start time. The input order is especially meaningful when the network consists of several interacting subnetworks. The waterfall sequence is helpful in assessing the project status at any point in time.
The Pioneer 11 encounter with Saturn has revealed the existence of a fully developed magnetosphere with high-energy trapped radiation about Saturn. The present paper gives a detailed summary of the energetic charged particle measurements, including the overall characteristics of the trapped electron, proton, and helium radiation, which was found to lie inside 20 Saturn radii from the planet, and the regions extending outward to beyond the planetary bow shocks and into the interplanetary medium.
Trapped-energy focusing transducers operating in the 2-5 MHz range have been fabricated by plating concentric rings of electrodes on a piezoelectric plate. The concentric ring structure acts as a Fresnel lens and can be used to obtain excellent lateral focusing of ultrasonic waves. The trapping is sufficiently strong to permit optimization of electrode spacings to suppress spurious virtual foci and ring sidelobes.
Three-dimensional distribution functions for energetic ions are studied numerically in the magnetosphere, through the magnetopause, and in the magnetosheath using a simple one-dimensional quasi-static model and ISEE 1 magnetopause crossing data for November 10, 1977. Quasi-trapped populations in the magnetosheath observed near flux transfer events (FTEs) are investigated, and it is shown that the population in the sheath appears to sandwich the FTE distributions. These quasi-trapped distributions are due to slow, large pitch angle, outward moving particles left behind by the outward rush of the ions more field-aligned at the time the flux was opened. It is found that sheath convective flows can map along the connected flux tube without drastically changing the distribution function, and results suggest that localized tangential fields above the upper limit may exist.
The April 15 and 28, 1978 solar flares appear to have 0.5-20 MeV protons trapped between a pair of shocks, and the large count rate enhancement observed, along with large ranges of radial distance and longitudinal angles, imply a prolongation of trapping for a period of weeks. The apparent ability of a shock whose plasma signature is faint to confine MeV protons in the outer solar system may have significant implications for cosmic ray studies. Analytical results also imply significant azimuthal asymmetry in plasma and energetic particle behavior, at distances as far as 16 AU from the sun. Combining these observations provides evidence for unexpectedly complex interactions in the outer solar system between energetic particles and solar wind plasma.
The interaction of trapped radiation with the ring of Jupiter is investigated. Because it is an identical problem, the rings of Saturn and Uranus are also examined. Data from the Pioneer II encounter, deductions for some of the properties of the rings of Jupiter and Saturn. Over a dozen Jupiter magnetic field models are available in a program that integrates the adiabatic invariants to compute B and L. This program is to label our UCSD Pioneer II encounter data with the most satisfactory of these models. The expected effects of absorbing material on the trapped radiation are studied to obtain the loss rate as a function of ring properties. Analysis of the particle diffusion problem rounds out the theoretical end of the ring absorption problem. Other projects include identification of decay products for energetic particle albedo off the rings and moons of Saturn and a search for flux transfer events at the Jovian magnetopause.
The observed spatial, directional and spectral characteristics of geomagnetically trapped heavy ions are reviewed. It is found that ions heavier than protons are significantly abundant in the earth's radiation belts, not only at low (ring-current) energies, but also at multi-MeV energies. Observations both at the geomagnetic equator and at low altitudes on the corresponding L-shell show the important roles played by the heavy ions. The heavy ion-to-proton flux ratio can exceed unity when compared at equal total ion energy. This is particularly the case at several MeV energies and in the outer radiation zone. In contrast, comparisons at equal energy per nucleon generally favor protons. The trapped fluxes of helium ions, of carbon, nitrogen and oxygen (CNO) ions, and of ions heavier than fluorine all exhibit high degrees of pitch angle anisotropy. Many of the observed radiation belt particle distribution characteristics are in agreement with first-order (quiet time) theoretical predictions, although some of the finer details await further research.