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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 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Cosmic muons, as messengers from the Universe

Penetrating from the outer space into the Earth atmosphere, primary cosmic rays are producing secondary radiation by the collisions with the air target subsequently decaying in hadrons, pions, muons, electrons and photons, phenomenon called Extensive air Shower (EAS). The muons, considered as the “penetrating” component, survive the propagation to the Earth and even they are no direct messenger of the Universe, they reflect the features of the primary particles. The talk gives a description of the development of the extensive air showers generating the secondary particles, especially the muon component. Results of the muon flux and of the muon charge ratio, (the ratio between the positive and the negative muons), obtained in different laboratories and in WILLI experiment, are shown. At the end, the contribution of the muons measured in EAS to the investigation of the nature of the primary cosmic rays is emphasized in KASCADE and WILLI-EAS experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Conditions for entangled photon emission from (111)B site-controlled pyramidal quantum dots

A study of highly symmetric site-controlled pyramidal In{sub 0.25}Ga{sub 0.75}As quantum dots (QDs) is presented. It is discussed that polarization-entangled photons can be also obtained from pyramidal QDs of different designs from the one already reported in Juska et al. [Nat. Photonics 7, 527 (2013)]. Moreover, some of the limitations for a higher density of entangled photon emitters are addressed. Among these issues are (1) a remaining small fine-structure splitting and (2) an effective QD charging under non-resonant excitation conditions, which strongly reduce the number of useful biexciton-exciton recombination events. A possible solution of the charging problem is investigated exploiting a dual-wavelength excitation technique, which allows a gradual QD charge tuning from strongly negative to positive and, eventually, efficient detection of entangled photons from QDs, which would be otherwise ineffective under a single-wavelength (non-resonant) excitation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Water adsorption on olivine(010) surfaces: Effect of alkali and transition metal cation doping

Dopants have the potential to locally modify water-olivine interactions, which can impact geological processes, such as weathering, CO 2 sequestration, and abiotic hydrocarbon generation. As a first step in understanding the role of dopants on the water structure and chemistry at water-olivine interfaces, water monomer adsorption on alkaline earth (AE) and transition metal (TM) doped forsterite(010) [Mg 2 SiO 4 (010)] surfaces was studied in this work using density functional theory (DFT). Dopants that occur in olivine minerals were considered and consisted of Ca, Sr, and Ba for the AE dopants and Cr, Mn, Fe, Co, and Ni for the TM dopants. The water molecule adsorbs on the olivine surface through a metal-water bond (Me–Ow) and a hydrogen bond with an adjacent surface lattice oxygen (Ox–Hw). A frontier orbital analysis reveals that the 1b 2 , 3a 1 , and 1b 1 (HOMO) of the water molecule are involved in the bonding. All of the TM dopants show strong net Me–Ow covalent bonding between 3a 1 and 1b 1 water orbitals and TM d states, while the AE dopants except for Mg 2 SiO 4 (010) show negligible Me–Ow covalent bonding. Both the AE and TM dopants show similar hydrogen bonding features involving both the 1b 2 and 3a 1 orbitals. While the AE cations show an overall lower Me–Ow covalent interaction, the AE dopants have strong electrostatic interactions between the positive metal cation and the negatively charged water dipole. A bonding model incorporating a linear combination of the covalent Me–Ow bond, the Ox–Hw hydrogen bond, the electrostatic interaction between the dopant cation and the H 2 O molecule, and the surface distortion energy is needed to capture the variation in the DFT adsorption energies on the olivine surfaces. The bonding analysis is able to identify the dominant contributions to water-dopant interactions and can serve as a basis for future studies of more realistic water-olivine interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Sheath formation around a dielectric droplet in a He atmospheric pressure plasma

Interactions at the interface between atmospheric pressure plasmas and liquids are being investigated to address applications ranging from nanoparticle synthesis to decontamination and fertilizer production. Furthermore, many of these applications involve activation of droplets wherein the droplet is fully immersed in the plasma and synergistically interacts with the plasma. To better understand these interactions, two-dimensional modeling of radio frequency (RF) glow discharges at atmospheric pressure operated in He with an embedded lossy dielectric droplet (tens of microns in size) was performed. The properties of the sheath that forms around the droplet were investigated over the RF cycle. The electric field in the bulk plasma polarizes the dielectric droplet while the electron drift in the external electric field is shadowed by the droplet. The interaction between the bulk and sheath electric fields produces a maximum in E/N (electric field/gas number density) at the equator on one side of the droplet where the bulk and sheath fields are aligned in the same direction and a minimum along the opposite equator. Due to resistive heating, the electron temperature T e is maximum 45° above and below the equator of the droplet where power deposition per electron is the highest. Although the droplet is, on the average, negatively charged, the charge density on the droplet is positive on the poles and negative on the equator, as the electron motion is primarily due to diffusion at the poles but due to drift at the equator.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Tracking performance of a single-crystal and a polycrystalline diamond pixel-detector

We present a comparative characterization of the performance of a single-crystal and a polycrystalline diamond pixel-detector employing the standard CMS pixel readout chips. Measurements were carried out at the Fermilab Test Beam Facility, FTBF, using protons of momentum 120 GeV/c tracked by a high-resolution pixel telescope. Particular attention was directed to the study of the charge-collection, the charge-sharing among adjacent pixels and the achievable position resolution. The performance of the single-crystal detector was excellent and comparable to the best available silicon pixel-detectors. The measured average detection-efficiency was near unity, ε = 0.99860±0.00006, and the position-resolution for shared hits was about 6 μm. On the other hand, the performance of the polycrystalline detector was hampered by its lower charge collection distance and the readout chip threshold. A new readout chip, capable of operating at much lower threshold (around 1 ke $-$ ), would be required to fully exploit the potential performance of the polycrystalline diamond pixel-detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

On the Benefits of a Symmetric Redox Flow Battery

Redox flow batteries (RFBs) are of interest for large-scale energy storage, but implementation has been challenged by their low energy density, high complexity, high cost, and insufficient lifetime due to several types of irreversible losses in the electrolyte. To address the issue of system complexity and irreversible losses, we have undertaken a detailed analysis of the concept of the symmetric redox flow battery, or SRFB, which relies on a single parent molecule as the charge storage species in both the positive and negative electrode reactions. Herein we elaborate on the operating principles and advantages of a SRFB and report the salient electrochemical properties of a class of organic molecules, diaminoanthraquinones (DAAQs) as promising candidates for use in SRFB redox electrolytes. Modeling of various modes of operation for SRFBs are presented along with an example of an operational, lab-scale SRFB based on a DAAQ system.

25 ENERGY STORAGE↗
DOE OSTI2019

Collaborative Research: Understanding Sheaths and Presheaths in Magnetized and Unmagnetized Plasmas

The common states of matter on Earth are solids, liquids and gases. Putting energy into gases can result in the 4th state of matter known as plasma, which consists of electrically charged particles (electrons and ions, both positive and negative) and neutral atoms and molecules. While uncommon on the Earth, plasma makes up more than 99% of the visible matter in the universe. Where plasma comes in contact with material boundaries, a thin region near the plasma boundary usually forms to isolate the plasma from the boundary. This thin region is called the plasma sheath. Experiments performed under aimed at improving our understanding of plasma sheaths and associated phenomena as fundamental to understanding all bounded plasmas. Plasma studied in this work are similar to those used in plasma applications such as the etching of semiconducting materials to make computer chips, in plasma space propulsion satellite engines, and used in experimental plasma fusion devices. The majority of experimental studies were carried out at the University of Wisconsin-Madison in close collaboration with Dr. Severn at the University of San Diego (USD), where most of diagnostic development for laser-induced fluorescence (LIF) measurements were carried out. USD is primarily an undergraduate institution. The award made possible outreach activities that promoted engagement of undergraduate students with diverse backgrounds in science, technology, engineering and mathematics (STEM) disciplines.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1979

Design, development, and flight of a spacecraft charging sounding rocket payload

Results of the flight of the spacecraft charging sounding rocket payload are given. The payload was designed to create charging by the emission of both positive ions and electrons. The relationship between environmental parameters and changes in vehicle potential during periods of emission was also studied.

Cohen, H. A.↗
NASA NTRS1983

Fiber optics for astronomical spectroscopy - The Medusa Spectrograph

An instrument has been built to obtain simultaneous spectra of 32 objects in the field of view of the Steward Observatory 2.3 m telescope. Short lengths of optical fiber are used to bring light from galaxy images at the focus of the telescope into a line at the spectrograph slit. This multi-fiber aperture plate instrument has been dubbed the Medusa Spectrograph. The Medusa is now producing spectra of about 100 galaxies per clear night. An optimized version of the instrument called the MX Spectrometer is being constructed to record spectra at a higher rate. This new instrument will have remotely positioned fibers under computer control. A Charge Coupled Device will be used as the spectrograph detector to allow sky subtraction, give increased dynamic range and provide more accurate wavelength calibration. Transmission characteristics of some commercial fibers are discussed, and the microlens optics used to match the telescope and the spectrograph to the fibers to avoid focal ratio degradation are described.

Hill, J. M.↗
NASA NTRS1985

Search for heavy antinuclei in the cosmic radiation

The existence of significant amounts of antimatter in the Universe is demonstrated through cosmic radiation. The data from the Danish-French Cosmic Ray Spectrometer on the HEAO-3 satellite offers an opportunity to search for heavy antinuclei, since all the relevant parameters (charge, velocity, arrival direction, and satellite position at the time of arrival) are measured for each recorded nucleus. Using the 22676 positive only events in the data seletion corresponding to L 1.5 as a measure of our exposure factor to heavy antinuclei and noting that no corresponding antinuclei were found, an upper limit (95% confidence) is given to the ratio of antinuclei to nuclei as 1.4 x .0001 for particles with Z 9. The upper limit resulting from this work is compared with previous results of searches for heavy antimatter in the cosmic radiation. It is seen that, if one regards only antiparticles heavier than fluorine, then the present result represents a reduced upper limit over previous data. When taken together, all the available experiment data now push the upper limit for the ratio of antiparticles to particles well below .0001.

Lund, N.↗
NASA NTRS1987

Statistically determined nickel cadmium performance relationships

A statistical analysis was performed on sealed nickel cadmium cell manufacturing data and cell matching data. The cells subjected to the analysis were 30 Ah sealed Ni/Cd cells, made by General Electric. A total of 213 data parameters was investigated, including such information as plate thickness, amount of electrolyte added, weight of active material, positive and negative capacity, and charge-discharge behavior. Statistical analyses were made to determine possible correlations between test events. The data show many departures from normal distribution. Product consistency from one lot to another is an important attribute for aerospace applications. It is clear from these examples that there are some significant differences between lots. Statistical analyses are seen to be an excellent way to spot those differences. Also, it is now proven beyond doubt that battery testing is one of the leading causes of statistics.

Gross, Sidney↗
NASA NTRS1990

Discharge transient coupling in large space power systems

Experiments have shown that plasma environments can induce discharges in solar arrays. These plasmas simulate the environments found in low earth orbits where current plans call for operation of very large power systems. The discharges could be large enough to couple into the power system and possibly disrupt operations. Here, the general concepts of the discharge mechanism and the techniques of coupling are discussed. Data from both ground and flight experiments are reviewed to obtain an expected basis for the interactions. These concepts were applied to the Space Station solar array and distribution system as an example of the large space power system. The effect of discharges was found to be a function of the discharge site. For most sites in the array discharges would not seriously impact performance. One location at the negative end of the array was identified as a position where discharges could couple to charge stored in system capacitors. This latter case could impact performance.

Stevens, N. John↗
NASA NTRS1990

Computer modeling of current collection by the CHARGE-2 mother payload

The three-dimensional computer codes NASCAP/LEO and POLAR have been used to calculate current collection by the mother payload of the CHARGE-2 rocket under conditions of positive and negative potential up to several hundred volts. For negative bias (ion collection), the calculations lie about 25 percent above the data, indicating that the ions were less dense, colder, or heavier than the input parameters. For positive bias (electron collection), NASCAP/LEO and POLAR calculations show similar agreement with the measurements at the highest altitudes. This agreement indicates that the current is classically magnetically limited, even during electron beam emission. However, the calculated values fall well below the data at lower altitudes. It is suggested that beam-plasma-neutral interactions are responsible for the high values of collected current at altitudes below 240 km.

Mandell, M. J.↗
NASA NTRS1991

Reinforced Positive Filler Paste For Lead/Acid Batteries

Lead-coated glass fibers extend battery life. Mixture of lead-coated glass fibers and positive paste form pellets of active material between grid wires of positive battery electrode. Fibers contribute to charge capacity, electrical conductivity, and mechanical stability of electrode.

Edwards, Dean B.↗
NASA NTRS1993

Pulsed, gridded electron reversal ionizer

The design and performance of a new-type source of negative ions is presented. This device retains the idea of the so-called reversal electron attachment detector to produce low-energy electrons by reversing electron trajectories at an electrode. Electrons are produced in the present device by several ribbon filaments that surround a cylindrical wire grid. They are accelerated through the grid, then decelerated to zero or near-zero velocity at the surface of a tube. The tube (anode) is perforated with small holes through which effuse the target molecules. Electrons attach to form either parent and/or fragment negative ions. Attachment takes place at a location above the anode corresponding to a match between the electron energy and the attachment resonance energy. Negative ions are pulsed out of the attachment region and focused onto the entrance plane of a quadrupole mass selector. Electron and ion trajectory calculations are presented and the performance illustrated with six molecules having attachment resonances in the range 0.0-2.2 eV. The detection sensitivity is below 1 part-per-trillion, with a calculated conversion rate of 1.3 percent. Signal nonlinearity is discussed in terms of ion space-charge effects. The device also produces positive ions, and an analogous treatment may be carried through to characterize its performance in this mode.

Boumsellek, S.↗
NASA NTRS1995

Effect of KOH concentration and anions on the performance of Ni-H2 battery positive plate

The capacity and voltage behavior of electrochemically impregnated sintered nickel positive plates was examined by galavanostatic charging; and discharging in a flooded electrolyte cell. Three different concentrations of KOH (40 percent, 31 percent, and 26 percent) and 31 percent KOH containing dissolved nitrate, sulfate or silicate were investigated. The end of charge voltage at C/10 charge and at 10 C showed the following order: 40 percent KOH is greater than 31 percent KOH alone and in the presence of the anions greater than 26 percent KOE. The middischarge voltage at C/2 discharge was higher in 26 percent KOH, almost the same for 31 percent KOH with and without the added contaminants and much lower for 40 percent KOH. The plate capacity was marginally affected by cycling in all cases except for 40 percent KOH where the capacity declined after 1000 cycles at 80 percent DOD. At the end of cycling the plate tested in the presence of sulfate and silicate experienced measurable weight loss as a result of active material extrusion. Cyclic voltammetry of miniature electrodes in 31 percent KOH showed that the second oxidation peak that corresponds to the formation of a different phase of oxidized Ni has a lower peak current at -5 C compared to 25 C and oxygen evolution occurs a higher potential at -5 C. The reduction peak (discharge reaction) is more polarized at 25 C compared to -5 C. The presence of silicate alters the potentials only marginally. The implications of these results in plate treatment and low temperature operation are discussed.

Vaidyanathan, H.↗
NASA NTRS1996

Effect of KOH Concentration and Anions on the Performance of a Ni-H2 Battery Positive Plate

The capacity and voltage behavior of electrochemically impregnated sintered nickel positive plates was examined by galvanostatic charging and discharging in a flooded electrolyte cell. Three different concentrations of potassium hydroxide (KOH) (40, 31, and 26 percent) and 31 percent KOH containing dissolved nitrate, sulfate, or silicate were investigated. The end-of-charge voltage at C/10 charge and at 10 degrees C showed the following order: 40 percent KOH greater than 31 percent KOH alone and in the presence of the anions greater than 26 percent KOH. The mid discharge voltage at C/2 discharge was higher in 26 percent KOH, almost the same for 31 percent KOH with and without added contaminants, and much lower for 40 percent KOH. The plate capacity was marginally affected by cycling in all cases except for 40 percent KOH, where the capacity declined after 1,000 cycles at 80 percent depth of discharge (DOD). At the end of cycling, all the plates tested experienced a weight loss, except in the case of 31 percent KOH, as a result of active material extrusion. Cyclic voltammetry of miniature electrodes in 31 percent KOH showed that the cathodic peak potentials are less polarized in the presence and absence of silicate at -5 degrees C compared to 25 degrees C indicating a slightly higher voltage during discharge in a Ni-H2 battery. Futhermore, the features of the current-potential profile were practically unchanged in the presence of silicate.

Vaidyanathan, Hari↗
NASA NTRS2010

Spatially-Resolved Beam Current and Charge-State Distributions for the NEXT Ion Engine

Plume characterization tests with the 36-cm NEXT ion engine are being performed at The Aerospace Corporation using engineering-model and prototype-model thrusters. We have examined the beam current density and xenon charge-state distribution as functions of position on the accel grid. To measure the current density ratio j++/j+, a collimated Eprobe was rotated through the plume with the probe oriented normal to the accel electrode surface at a distance of 82 cm. The beam current density jb versus radial position was measured with a miniature planar probe at 3 cm from the accel. Combining the j++/j+ and jb data yielded the ratio of total Xe+2 current to total Xe+1 current (J++/J+) at forty operating points in the standard throttle table. The production of Xe+2 and Xe+3 was measured as a function of propellant utilization to support performance and lifetime predictions for an extended throttle table. The angular dependence of jb was measured at intermediate and far-field distances to assist with plume modeling and to evaluate the thrust loss due to beam divergence. Thrust correction factors were derived from the total doubles-to-singles current ratio and from the far-field divergence data

Pollard, James E.↗