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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Ionic charge states of solar energetic particles - Effects of flare X-rays

Ionic charge states of solar energetic particles (SEP) from three flares have been reported by Luhn et al. (1984). Interpretations of the mean charges in terms of a source temperature Ts (assuming collisional ionization equilibrium) yield inconsistent results. For Mg, the required Ts (up to 8 x 10 to the 6th K) are larger than for N and Si by factors of up to 5. Here it is pointed out that flare X-rays photoionize the ambient corona, causing apparent ionization temperatures there to exceed the local electron temperature, Te. Using realistic flare X-ray fluxes, it is shown that the charge data for six elements (C, N, Ne, Mg, Si, and S) can be fitted if the source is at coronal temperatures (Te = 1-2 x 10 to the 6th K), but the ionization equilibrium is radiation dominated. For oxygen, a slight inconsistency persists in the three flares.

Mullan, D. J.↗
NASA NTRS1975

Implications of observed charge states of low-energy solar cosmic rays

Recent measurements of the charge states of low-energy (about 100 keV/nucleon) solar cosmic rays at 1 AU are discussed. The measurements are consistent with models involving charge equilibrium with neutral matter at the sun only if the particles lose about 90% of their energy owing to adiabatic deceleration in the solar wind. Such an energy loss is shown to be possible only if the diffusion coefficient for 1-MeV/nucleon particles is smaller than 100 quintillion sq cm per sec. The implications of these results for models of solar-cosmic-ray acceleration are discussed.

Jokipii, J. R.↗
NASA NTRS1995

SWICS/Ulysses and MASS/wind observations of solar wind sulfur charge states

As Ulysses journeys from the southern to the northern solar pole, the newly launched Wind spacecraft is monitoring the solar wind near 1 AU, slightly upstream of the Earth. Different solar wind structures pass over both spacecraft as coronal holes and other features rotate in and out of view. Ulysses and Wind are presently on opposing sides of the sun allowing us to monitor these streams for extended periods of time. Composition measurements made by instruments on both spacecraft provide information concerning the evolution and properties of these structures. We have combined data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and the high mass resolution spectrometer (MASS) on Wind to determine the charge state distribution of sulfur in the solar wind. Both instruments employ electrostatic deflection with time-of-flight measurement. The high mass resolution of the MASS instrument (M/Delta-M approximately 100) allows sulfur to be isolated easily while the stepping energy/charge selection provides charge state information. SWICS measurements allow the unique identification of heavy ions by their mass and mass/charge with resolutions of M/Delta-M approximately 3 and M/q/Delta(M/q) approximately 20. The two instruments complement each other nicely in that MASS has the greater mass resolution while SWICS has the better mass/charge resolution and better statistics.

Cohen, C. M. S.↗
DOE OSTI2026

Phosphoserine Charge State Drives Ion Condensation and Spatial Polyamine Presentation in Multirepeat Silaffin

Diatom silaffins direct silica biomineralization through heavily post-translationally modified repeat domains, yet how these modifications reshape the multirepeat conformational ensemble remains unknown. We report all-atom MD simulations of a 195-residue construct spanning repeats R1–R7 of Sil1p from Cylindrotheca fusiformis, carrying the full complement of native PTMs: phosphoserine (pSer), long-chain polyamines (LCPA), dimethyllysine (MLY), and trimethylhydroxylysine phosphate (TPL). We simulated three variants (Native, P1/singly deprotonated phosphate, and P2/doubly deprotonated phosphate) at two NaCl concentrations in triplicate for 500 ns each. All systems disorder from the AlphaFold 3 starting structure. Phosphate charge state, not ionic strength, is the dominant control of ensemble compaction and ion organization. Doubly deprotonated phosphate organizes an extensive Na + condensation shell (∼100 ions, 20% of box Na + ) and a heterogeneous bridging network that integrates both pSer and TPL phosphate groups. The resulting ensemble is compact with LCPA side chains exhibiting above-median solvent accessibility in 84% of simulation frames in P2 at 300 mM. This is higher than any other condition we simulated and indicates that polyamine groups are preferentially surface-presented in the most compact, ion-organized state. A charge-neutralization control confirms that this compact state is a structured intermediate maintained by the bridging network, not a simple collapsed globule. Here, this repeat-scale spatial organization is not captured by single-repeat peptide studies. Understanding the dynamics, mechanism, and spatial organization of PTM-rich silaffin at the repeat scale is a step closer to hierarchical biomimetic materials beyond simple silica morphologies.

Amines↗
DOE OSTI2021

Ultrafast X-ray scattering offers a structural view of excited-state charge transfer

Intramolecular charge transfer and the associated changes in molecular structure in N,N'-dimethylpiperazine are tracked using femtosecond gas-phase X-ray scattering. The molecules are optically excited to the 3p state at 200 nm. Following rapid relaxation to the 3s state, distinct charge-localized and charge-delocalized species related by charge transfer are observed. The experiment determines the molecular structure of the two species, with the redistribution of electron density accounted for by a scattering correction factor. The initially dominant charge-localized state has a weakened carbon–carbon bond and reorients one methyl group compared with the ground state. Subsequent charge transfer to the charge-delocalized state elongates the carbon–carbon bond further, creating an extended 1.634 Å bond, and also reorients the second methyl group. At the same time, the bond lengths between the nitrogen and the ring-carbon atoms contract from an average of 1.505 to 1.465 Å. The experiment determines the overall charge transfer time constant for approaching the equilibrium between charge-localized and charge-delocalized species to 3.0 ps.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Elucidating Design Rules toward Enhanced Solid-State Charge Transport in Oligoether-Functionalized Dioxythiophene-Based Alternating Copolymers

This study investigates the solid-state charge transport properties of the oxidized forms of dioxythiophene-based alternating copolymers consisting of an oligoether-functionalized 3,4-propylenedioxythiophene (ProDOT) copolymerized with different aryl groups, dimethyl ProDOT (DMP), 3,4-ethylenedioxythiophene (EDOT), and 3,4-phenylenedioxythiophene (PheDOT), respectively, to yield copolymers P(OE3)-D, P(OE3)-E, and P(OE3)-Ph. At a dopant concentration of 5 mM FeTos 3 , the electrical conductivities of these copolymers vary significantly (ranging between 9 and 195 S cm –1 ) with the EDOT copolymer, P(OE3)-E, achieving the highest electrical conductivity. UV–vis–NIR and X-ray spectroscopies show differences in both susceptibility to oxidative doping and extent of oxidation for the P(OE3) series, with P(OE3)-E being the most doped. Wide-angle X-ray scattering measurements indicate that P(OE3)-E generally demonstrates the lowest paracrystallinity values in the series, as well as relatively small π–π stacking distances. The significant (i.e., order of magnitude) increase in electrical conductivity of doped P(OE3)-E films versus doped P(OE3)-D or P(OE3)-Ph films can therefore be attributed to P(OE3)-E exhibiting both the highest carrier ratios in the P(OE3) series, along with good π–π overlap and local ordering (low paracrystallinity values). Furthermore, these trends in the extent of doping and paracrystallinity are consistent with the reduced Fermi energy level and transport function prefactor parameters calculated using the semilocalized transport (SLoT) model. Observed differences in carrier ratios at the transport edge (c t ) and reduced Fermi energies [η(c)] suggest a broader electronic band (better overlap and more delocalization) for the EDOT-incorporating P(OE3)-E polymer relative to P(OE3)-D and P(OE3)-Ph. Ultimately, we rationalize improvements in electrical conductivity due to microstructural and doping enhancements caused by EDOT incorporation, a structure–property relationship worth considering in the future design of highly electrically conductive systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Iron charge states observed in the solar wind

Solar wind measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE-3 are reported. The low energy section of approx the ULECA sensor selects particles by their energy per charge (over the range 3.6 keV/Q to 30 keV/Q) and simultaneously measures their total energy with two low-noise solid state detectors. Solar wind Fe charge state measurements from three time periods of high speed solar wind occurring during a post-shock flow and a coronal hole-associated high speed stream are presented. Analysis of the post-shock flow solar wind indicates the charge state distributions for Fe were peaked at approx +16, indicative of an unusually high coronal temperature (3,000,000 K). In contrast, the Fe charge state distribution observed in a coronal hole-associated high speed stream peaks at approx -9, indicating a much lower coronal temperature (1,400,000 K). This constitutes the first reported measurements of iron charge states in a coronal hole-associated high speed stream.

Ipavich, F. M.↗
NASA NTRS1984

Ionic charge states of N, Ne, Mg, Si and S in solar energetic particle events

The mean ionic charges and source-region temperatures of flare-accelerated N, Ne, Mg, Si and S in three large solar-energetic-particle events during 1978-1979 are determined from ISEE-3 observations, extending the findings of Hovestadt et al. (1981) and Gloeckler et al. (1981) for C, He, O, and Fe. The results are presented in tables and graphs, and the charge states are shown to correspond to different source temperatures even in the same flare, assuming equilibration in the hot plasma. The electron temperatures range from 2 x 10 to the 6th K for C, N, O, Si, and S, 4 x 10 to the 6th K for Ne and Fe, and 7 x 10 to the 6th K for Mg. The possibility that these temperature inconsistencies reflect different stages in the approach to equilibrium is considered.

Luhn, A.↗
NASA NTRS1997

Charge state composition in coronal hole and CME related solar wind: Latitudinal variations observed by Ulysses and WIND

Iron charge states in recurrent coronal hole-associated solar wind flows are obtained in the ecliptic by WIND/SMS, while measurements of iron and silicon from the polar coronal holes are available from Ulysses/SWICS. Ulysses/SWICS also provides ion composition of coronal mass ejection (CME)-related solar wind. Both coronal hole-associated and CME-related solar wind charge charges show heliographic latitudinal variations.

Galvin, A. B.↗
DOE OSTI2020

Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X

Here, the plasma volume averaged impurity confinement of selected charge states and impurity species has been characterized for the Stellarator Wendelstein 7-X (W7-X), covering a wide range of atomic charges (Z = 12–44) and atomic masses (M = 28–184). A comparison of the experimental findings to theoretical neoclassical and turbulent transport expectations suggests, aside from/in addition to the neoclassical transport, an additional significant anomalous transport mechanism, which is not inconsistent with the predictions of a turbulence dominated impurity transport and is in agreement with the experimental results from recent transport studies based on the direct measurements of impurity diffusion profiles, performed at W7-X.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1977

An experimental test for the charge state of the 'anomalous' helium component

Observations of phase lags between intensity variations for various particle species and energy ranges in the low-energy galactic cosmic radiation during the general intensity decrease observed in 1974-1975 show that, for particles whose charge state is known (i.e., 'normal' cosmic-ray components), particles with higher rigidities respond more quickly to changes in modulation conditions than do those with lower rigidities. When compared with particles of known energy and charge, the behavior of the 'anomalous' low-energy helium component is consistent with these observations only if the helium is singly rather than doubly charged.

Mckibben, R. B.↗
NASA NTRS2004

SEP Time-to-Maximum (TTM) Studies and the Ionic Charge States of Solar Heavy Ions

1. We published a report on the TTM method and presented the results at the 28 International Cosmic Ray Conference. Included in this paper were our results on the energy-dependent charge state of Fe in the 200 1 April 15 ground- level event, the largest of Cycle 23. We showed that our results agreed well with direct measurements from SAMPEX in this event. We also presented results for the 2001 April 14 event, one of the largest impulsive events of Cycle 23. 2. We extracted TTM values for protons and ions of various energies in approx. 50 SEP events in Cycle 23, using time profiles measured by ACE, Wind, GOES, IMPS, SOHO, and SAMPEX. This event sample included many large gradual events, as well as several impulsive events. The TTM analyses typically yielded approx. 300 datapoints per event. 3. We used these data to make preliminary event classifications according to: (a) shapes of the rigidity and/or speed dependence of TTMs in each event; (b) behavior of proton TTMs compared to that of heavier ions; and (c) the behavior of Fe TTMs compared to that of lighter Z greater than I ions. 4. We cross-checked proton fluence and TTM values from 8 instruments on 6 satellites, so as to understand the origin of systematic instrument-to-instrument discrepancies. By also comparing the observed proton spectra, it was possible to extract correction factors to the nominal proton energy bins that removed or greatly reduced the instrument-to-instrument spread among proton TTMs. 5. We began comparisons of proton and He-4 TTM values in some particularly well measured, large SEP events measured by IMP8 in Cycles 21 and 22 when the instruments onboard were functioning better. It is hoped that these data will provide a better understanding of event-to-event variation in the functional dependence of TTMs on velocity and rigidity.

Tylka, Allan J.↗
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.↗
NASA NTRS1995

The mean ionic charge state of solar energetic Fe ions above 200 MeV per nucleon

We have analyzed the geomagnetic transmission of solar energetic Fe ions at approximately 200-600 MeV per nucleon during the great solar energetic particle (SEP) events of 1989 September-October. By comparing fluences from the Chicago charged-particle telescope on IMP-8 in interplanetary space and from NRL's Heavy Ions in Space (HIIS) experiment aboard the Long Duration Exposure Facility (LDEF) in low-Earth orbit, we obtain a mean ionic charge (Q(sub 3)) = 14.2 +/- 1.4. This result is significantly lower than (Q) observed at approximately 1 MeV per nucleon in impulsive, He-3 rich SEP events, indicating that neither acceleration at the flare site nor flare-heated plasma significantly contributes to the high-energy Fe ions we observe. But it agrees well with the (Q) observed in gradual SEP events at approximately 1 MeV per nucleon, in which ions are accelerated by shocks driven by fast coronal mass ejections, and hence shows that particles are accelerated to very high energies in this way. We also note apparent differences between solar wind and SEP charge state distributions, which may favor a coronal (rather than solar wind) seed population or may suggest additional ionization in the ambient shock-region plasma.

Tylka, A. J.↗
NASA NTRS1992

Silicon and oxygen charge state distributions and relative abundances in the solar wind measured by SWICS on Ulysses

We report an initial survey of solar wind silicon and oxygen using data obtained with the Ulysses Solar Wind Ion Composition Spectrometer. In this study, the O(+7)/O(+6) ratio is used to group silicon counts accumulated over a two month period. Results on Si charge state distributions, relative Si/O abundances, and associated proton kinetic temperature and speed distributions are presented.

Galvin, A. B.↗
DOE OSTI2022

Binary Fe/Mn-Based Nanocomposites as Li-Free Cathode Materials for Li Batteries Assembled in Charged State

Li-ion batteries play important roles in this mobile society. The ever-increasing demand for energy storage, particularly from electric vehicles, requires next-generation Li batteries with higher energy density and better safety. In contrast to existing Li-ion batteries using lithiated cathodes and Li-free anodes, we explore Li-free cathodes coupled with lithium/ lithiated anodes in order to construct new Li batteries assembled in a charged state. Here, two highly promising Li-free cathode materials of 1-D FeOF nanorods and 2-D monolayer MnO 2 nanosheets are integrated to make FeOF@MnO 2 nanocomposites. FeOF nanorods are sandwiched by monolayer MnO 2 nanosheets where FeOF nanoparticles could prevent the restacking of the monolayer MnO 2 nanosheets and the presence of monolayer MnO 2 nanosheets could enhance the electrical integration of the FeOF nanorods. Synergistic effects of the binary Fe/Mn-based cathodes can lead to both high voltage and high capacity, compared to individual components. Electrochemical evaluation reveals that binary Fe/Mn-based Li-free cathodes demonstrate promising performances and are worthy of further investigation and optimization.

25 ENERGY STORAGE↗
DOE OSTI2020

Charge state dynamics and optically detected electron spin resonance contrast of shallow nitrogen-vacancy centers in diamond

Nitrogen-vacancy (NV) centers in diamond can be used for nanoscale sensing with atomic resolution and sensitivity; however, it has been observed that their properties degrade as they approach the diamond surface. Here we report that in addition to degraded spin coherence, NV centers within nanometers of the surface can also exhibit decreased fluorescence contrast for optically detected electron spin resonance (OD-ESR). We demonstrate that this decreased OD-ESR contrast arises from charge state dynamics of the NV center, and that it is strongly surface-dependent, indicating that surface engineering will be critical for nanoscale sensing applications based on color centers in diamond.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗