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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Plasma-assisted physical vapor deposition surface treatments for tribological control

In any mechanical or engineering system where contacting surfaces are in relative motion, adhesion, wear, and friction affect reliability and performance. With the advancement of space age transportation systems, the tribological requirements have dramatically increased. This is due to the optimized design, precision tolerance requirements, and high reliability expected for solid lubricating films in order to withstand hostile operating conditions (vacuum, high-low temperatures, high loads, and space radiation). For these problem areas the ion-assisted deposition/modification processes (plasma-based and ion beam techniques) offer the greatest potential for the synthesis of thin films and the tailoring of adherence and chemical and structural properties for optimized tribological performance. The present practices and new approaches of applying soft solid lubricant and hard wear resistant films to engineering substrates are reviewed. The ion bombardment treatments have increased film adherence, lowered friction coefficients, and enhanced wear life of the solid lubricating films such as the dichalcogenides (MoS2) and the soft metals (Au, Ag, Pb). Currently, sputtering is the preferred method of applying MoS2 films; and ion plating, the soft metallic films. Ultralow friction coefficients (less than 0.01) were achieved with sputtered MoS2. Further, new diamond-like carbon and BN lubricating films are being developed by using the ion assisted deposition techniques.

Spalvins, Talivaldis↗
NASA NTRS1999

Acceleration Processes in the Cusp -- Observations by the FAST Satellite

The FAST spacecraft has encountered the Earth's cusp regions near its apogee of 4175 km on numerous occasions during its first two and half years of operations. The cusp encounters are identified by their signatures of keV dispersed ion injections of solar wind origin. The FAST instruments reveal a complex microphysics inherent to many, but not all, of the cusp regions encountered by the spacecraft, that often include upgoing ion beams within regions of downgoing electrons that may appear as series of inverted-V features with energies near a few hundred eV. In many instances, upgoing electron beams have also been observed. Intense (> 100 mV/m) spikey DC-coupled electric fields and plasma waves are common features of the cusp encounters which also provide evidence for the presence of such local acceleration processes. In some cases, the FAST data show clear modulation of the precipitating magnetosheath ions indicative that they are affected by local electric potentials, as evidenced by simultaneous electron acceleration within such intervals. Furthermore, the acceleration events are sometimes organized with an apparent cellular structure that suggest Alfven waves or other large scale phenomena are controlling the localized potentials. We examine several cusp encounters in detail in order to study the complex relation of the cusp energetic particle populations with the plasma waves and DC electric fields.

Pfaff, R. F.↗
NASA NTRS1999

Acceleration Processes in the Cusp: Observations by the FAST Satellite

The Fast Auroral Snapshot (FAST) spacecraft has encountered the Earth's cusp regions near its apogee of 4175 km on numerous occasions during its first two and half years of operations. The cusp encounters are identified by their signatures of keV dispersed ion injections of solar wind origin. The FAST instruments reveal a complex microphysics inherent to many, but not all, of the cusp regions encountered by the spacecraft, that often include upgoing ion beams within regions of downgoing electrons that may appear as series of inverted-V features with energies near a few hundred eV. In many instances, upgoing electron beams have also been observed. Intense (> 100 mV/m) spikey DC-coupled electric fields and plasma waves are common features of the cusp encounters which also provide evidence for the presence of such local acceleration processes. In some cases, the FAST data show clear modulation of the precipitating magnetosheath ions indicative that they are affected by local electric potentials, as evidenced by simultaneous electron acceleration within such intervals. Furthermore, the acceleration events are sometimes organized with an apparent cellular structure that suggest Alfv6n waves or other large scale phenomena are controlling the localized potentials. We examine several cusp encounters in detail in order to study the complex relation of the cusp energetic particle populations with the plasma waves and DC electric fields.

Pfaff, R. F.↗
NASA NTRS2001

Ion Propulsion Development Projects in US: Space Electric Rocket Test I to Deep Space 1

The historical background and characteristics of the experimental flights of ion propulsion systems and the major ground-based technology demonstrations are reviewed. The results of the first successful ion engine flight in 1964, Space Electric Rocket Test (SERT) I, which demonstrated ion beam neutralization, are discussed along with the extended operation of SERT II starting in 1970. These results together with the technologies employed on the early cesium engine flights, the applications technology satellite series, and the ground-test demonstrations, have provided the evolutionary path for the development of xenon ion thruster component technologies, control systems, and power circuit implementations. In the 1997-1999 period, the communication satellite flights using ion engine systems and the Deep Space 1 flight confirmed that these auxiliary and primary propulsion systems have advanced to a high level of flight readiness.

Sovey, James S.↗
DOE OSTI2023

Impact of β n and spectrum of n = 1 applied fields on fast ion losses in DIII-D

Abstract The effect of n = 1 magnetic perturbations (MPs) on prompt fast ion losses in DIII-D has been investigated using the light ion beam probe technique. The effect of normalized beta, β n , and the plasma response to the MPs is studied for several MP spectra. Magnetics data show a strong dependence of plasma response to β n that depends on the phase difference in perturbation coils, Δ ϕ U L . For most phases, the response increases with β n , however, the response is suppressed for phases between 180 ∘ and 240 ∘ . Experimental data from scintillator based fast ion loss detectors shows that relative fluctuation of lost ions (20%–30% of the steady signal) does not diminish across the L- to H-mode transition for Δ ϕ U L = 240 ∘ , despite the 34% decrease in radial response field and 50% decrease in poloidal response field. Simulations of the DIII-D discharges using M3D-C1 and ASCOT5 find that prompt losses from neutral beam injection in each investigated case hit the first wall at several concentrated locations: the vessel floor, midplane diagnostic ports, vessel ceiling, and inner wall. Simulated losses from co-injection neutral beams are born outside the last closed flux surface, corresponding to radial orbit displacements of 3–6 cm due to the MPs.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1999

A Synopsis of Ion Propulsion Development Projects in the United States: SERT 1 to Deep Space I

The historical background and characteristics of the experimental flights of ion propulsion systems and the major ground-based technology demonstrations were reviewed. The results of the first successful ion engine flight in 1964, SERT I which demonstrated ion beam neutralization, are discussed along with the extended operation of SERT II starting in 1970. These results together with the technology employed on the early cesium engine flights. the Applications Technology Satellite (ATS) series, and the ground-test demonstrations, have provided the evolutionary path for the development of xenon ion thruster component technologies, control systems, and power circuit implementations. In the 1997-1999 period, the communication satellite flights using ion engine systems and the Deep Space I flight confirmed that these auxiliary and primary propulsion systems have advanced to a high-level of flight-readiness.

Sovey, James S.↗
DOE OSTI2022

Phase instabilities in austenitic steels during particle bombardment at high and low dose rates

Disruption of phase stability by energetic particle bombardment is a major challenge in designing advanced radiation-tolerant alloys and ion beam processing of nanocomposites. Particularly, ballistic dissolution susceptibility of different solute nanocluster species in alloys is poorly understood. Here, low dose rate neutron irradiations were conducted on a Fe-Cr-Ni based austenitic steel in the BOR-60 reactor (9.4 × 10 -7 dpa/s, 318 °C) followed by accelerated dose rate ion irradiations at multiple temperatures ( 10 -3 dpa/s, 380 – 420 °C). Using atom probe tomography, the stability of radiation-enhanced Cu-rich and radiation-induced Ni-Si-Mn-rich nanoclusters was evaluated. During neutron irradiation, Cu-rich clusters nucleated with their core concentrations progressively increasing with dose, while Ni-Si-Mn-rich clusters formed and evolved into G-phase precipitates. Ion irradiations dramatically altered the nanoclusters. Cu-rich clusters were ballistically dissolved, but Ni-Si-Mn-rich clusters remained stable and coarsened with dose at 400 and 420 °C, highlighting that different nanocluster species in a single microstructure can have innately distinct ballistic dissolution susceptibilities. Solute-specific recoil rates were incorporated into the Heinig precipitate stability model, which shows that in addition to radiation-enhanced diffusion, recovery from ballistic dissolution depends on solute concentration gradient near cluster interfaces. Finally, the combined experimental-modeling study quantified the critical temperatures and damage rates where ballistic dissolution dominates for each cluster species.

36 MATERIALS SCIENCE↗
NASA NTRS1981

SERT II thrusters - Still ticking after eleven years

The Space Electric Rocket Test II (SERT II) spacecraft was launched in 1970 with a primary objective of demonstrating long-term operation of a space electric thruster system. An overview is presented of all the SERT II testing conducted during the time from 1970 to 1981. Thruster testing and interaction results are considered, taking into account ion beam thrusting, distant neutralization, and the plasma beam thrust. In a discussion of durability testing, attention is given to the main cathodes, the neutralizer cathodes, the main keeper insulator, the H.V. grid insulators, the neutralizer propellant tanks, and the main propellant tanks. The most important result of the study is related to the confidence gained that mercury bombardment ion thruster systems can be built and operated in space on a routine basis with the same lifetime and performance as measured in ground testing.

Kerslake, W. R.↗
NASA NTRS2003

Differential Sputtering Behavior of Pyrolytic Graphite and Carbon-Carbon Composite Under Xenon Bombardment

A differential sputter yield measurement technique is described, which consists of a quartz crystal monitor that is swept at constant radial distance from a small target region where a high current density xenon ion beam is aimed. This apparatus has been used to characterize the sputtering behavior of various forms of carbon including polycrystalline graphite, pyrolytic graphite, and PVD-infiltrated and pyrolized carbon-carbon composites. Sputter yield data are presented for pyrolytic graphite and carbon-carbon composite over a range of xenon ion energies from 200 eV to 1 keV and angles of incidence from 0 deg (normal incidence) to 60 deg .

Williams, John D.↗
DOE OSTI2020

Durability test of a flowing-water target for isotope harvesting

A high intensity proton irradiation was performed with the flowing-water isotope harvesting target at the University of Wisconsin-Madison Cyclotron Laboratory to measure the rate of degradation of the target shell during irradiation conditions. The beam reached an intensity of 34 µA by the end of the irradiation and covered an area of 0.7 cm 2 on the target. Radiolysis products, such as H 2 O 2 , H 2 , and O 2 , were measured in the bulk water of the system and found to be present at much lower levels than predicted by literature escape yields. Radionuclides formed in the target shell were measured in the system water as a radiotracer for target degradation. Using a simple, beam intensity dependent model, a corrosion rate of 1.5E-6 μm/(μA*s) was found to match the measured radiotracer activities at various points in the irradiation. Furthermore, this rate was used to extrapolate the lifetime of future isotope harvesting targets at the NSCL and FRIB, using the areal power density of different ion beams to scale the corrosion rate.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1988

A predicted energetic ion signature of a neutral line in the geomagnetic tail

Under certain assumptions one can predict the formation of a magnetic neutral line on theoretical grounds, generally as a result of an unstable current sheet. Neutral points also seen to form spontaneously in a wide variety of plasma simulatioons, from MHD to fully kinetic. Hence, such magnetic null regions are central to some models of magnetotail energization and magnetic substorms. Yet the observational evidence for such regions remains controversial. This paper presents a new signature of a neutral line: the field-aligned ion beam characteristic of current sheet acceleration becomes dispersed into a 'ridge' in the velocity space distribution function as a neutral line is approached. The results were obtained using single-particle simulations in a fixed magnetic field model. The origin of the ridge is shown to be due to initially earthward going ions which pass through the neutral line region. These ions come from a smaller part of the initially antiearthward flowing distribution, generating the depletion of the distribution function below the ridge.

Martin, R. F., Jr.↗
NASA NTRS1994

Mutagenesis in human cells with accelerated H and Fe ions

The overall goals of this research were to determine the risks of mutation induction and the spectra of mutations induced by energetic protons and iron ions at two loci in human lymphoid cells. During the three year grant period the research has focused in three major areas: (1) the acquisition of sufficient statistics for human TK6 cell mutation experiments using Fe ions (400 MeV/amu), Fe ions (600 MeV/amu) and protons (250 MeV/amu); (2) collection of thymidine kinase- deficient (tk) mutants or hypoxanthine phosphoribosyltransferase deficient (hprt) mutants induced by either Fe 400 MeV/amu, Fe 600 MeV/amu, or H 250 MeV/amu for subsequent molecular analysis; and (3) molecular characterization of mutants isolated after exposure to Fe ions (600 MeV/amu). As a result of the shutdown of the BEVALAC heavy ion accelerator in December 1992, efforts were rearranged somewhat in time to complete our dose-response studies and to complete mutant collections in particular for the Fe ion beams prior to the shutdown. These goals have been achieved. A major effort was placed on collection, re-screening, and archiving of 3 different series of mutants for the various particle beam exposures: tk-ng mutants, tk-sg mutants, and hprt-deficient mutants. Where possible, groups of mutants were isolated for several particle fluences. Comparative analysis of mutation spectra has occured with characterization of the mutation spectrum for hprt-deficient mutants obtained after exposure of TK6 cells to Fe ions (600 MeV/amu) and a series of spontaneous mutants.

Kronenberg, Amy↗
NASA NTRS2015

GCR Simulator Reference Field and a Spectral Approach for Laboratory Simulation

The galactic cosmic ray (GCR) simulator at the NASA Space Radiation Laboratory (NSRL) is intended to deliver the broad spectrum of particles and energies encountered in deep space to biological targets in a controlled laboratory setting. In this work, certain aspects of simulating the GCR environment in the laboratory are discussed. Reference field specification and beam selection strategies at NSRL are the main focus, but the analysis presented herein may be modified for other facilities. First, comparisons are made between direct simulation of the external, free space GCR field and simulation of the induced tissue field behind shielding. It is found that upper energy constraints at NSRL limit the ability to simulate the external, free space field directly (i.e. shielding placed in the beam line in front of a biological target and exposed to a free space spectrum). Second, variation in the induced tissue field associated with shielding configuration and solar activity is addressed. It is found that the observed variation is likely within the uncertainty associated with representing any GCR reference field with discrete ion beams in the laboratory, given current facility constraints. A single reference field for deep space missions is subsequently identified. Third, an approach for selecting beams at NSRL to simulate the designated reference field is presented. Drawbacks of the proposed methodology are discussed and weighed against alternative simulation strategies. The neutron component and track structure characteristics of the simulated field are discussed in this context.

Slaba, Tony C.↗
DOE OSTI2021

Proton irradiation-induced blistering in UO2

Abstract Proton (H + ) irradiation effects in polycrystalline UO 2 have been studied. The irradiation was carried out using three ion energies and two different ion fluxes at 600 °C. Scanning electron microscopy (SEM) investigations showed that significant surface flaking took place. Focused ion beam (FIB) milling in SEM was successfully applied for extracting lamellas from uneven blistered surfaces for transmission electron microscopy (TEM) investigations allowing detailed investigations for the degradation mechanisms. High-resolution TEM for the flaked UO 2 surfaces revealed that the implanted H + formed sharp two-dimensional cavities at the peak ion-stopping region instead of diffusing to the matrix. The resulting lateral stress likely caused UO 2 surface deterioration in good agreement with previous blistering and flaking studies on crystalline materials. Graphical abstract

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1991

Characteristics of ring-cusp discharge chambers

Measurements have been obtained for the operating characteristics of a 30 cm diameter ring-cusp ion thruster (RCIT), quantitatively comparing its performance parameters to those of a divergent-field J-series cluster of the same size. The high level of performance established for the RCIT is due to its maintenance of both a higher primary-electron population and Maxwellian-electron temperature, as the beam-ion production cost is reduced to its baseline value. Ion losses to the discharge-chamber walls can be reduced by an applied electrostatic field.

Matossian, J. N.↗
NASA NTRS2016

Organic Aggregates with (delta)D and delta(sup 15)N Anomalies in the Zag Clast Revealed by STXM and NanoSIMS

Xenolithic clasts are often found in a wide variety of meteorite groups. Some ordinary chondrite clasts are interesting since these clasts might have originated from Ceres which shares crossing orbits with a possible ordinary chondrite parent body, Hebe. The Zag meteorite contains a dark clast dominated by saponite, serpentine, carbonates, sulfides, magnetite, minor olivine and pyroxene, which is consistent with formation on a large, carbonaceous, aqueously active body, e.g., Ceres. Abundant large C-rich grains up to 20 microns were found in the Zag clast as well. Such large C-rich grains are unique among any other meteorites in our knowledge, and will provide important clues to decipher the origin of the clast and accretion history. C-rich grains were selected in the Zag dark clast using SEM and approximately 100 nm-thick sections were prepared using a focused ion beam (FIB) at NASA-JSC. The sections were analyzed using the scanning transmission X-ray microscope (STXM) on beamline 5.3.2.2 at Advanced Light Source, LBNL, and BL-13A at the Photon Factory, KEK. Subsequently, the FIB section was analyzed for H, C and N isotopic compositions using a CAMECA NanoSIMS 50L ion microprobe at Kochi Institute for Core Sample Research, JAMSTEC

Kebukawa, Y.↗
DOE OSTI2022

Determination of the characteristic magnetic pre-sheath length at divertor surfaces using micro-engineered targets on DiMES at DIII-D

The magnetic pre-sheath (MPS) width, L MPS , is a critical parameter to define the sheath potential, which controls the ion trajectory of low-Z species (D, T, He, and C), as well as the prompt re-deposition of high-Z species. In this work, to determine L MPS , we fabricated micro-trenches (30×30×4 µm) via focused ion beam (FIB) milling on a silicon surface and exposed them to L-mode deuterium plasmas in DIII-D via the Divertor Material Evaluation System (DiMES) removable sample exposure probe. The areal distribution of impurity depositions, mainly consisting of carbon, was measured by energy-dispersive X-ray spectroscopy (EDS) to reveal the deuterium ion shadowing effect on the trench floors. The carbon deposition profiles showed that the erosion was maximized for the azimuthal direction of φ = -40° (referenced to the toroidal magnetic field direction) as well as the polar angle of θ = 80°. A Monte Carlo equation-of-motion model, based on a collisionless MPS, was used to calculate the azimuthal and polar deuterium ion angle distributions (IADs) for a range of L MPS = k × ρ i , where ρ i is the ion gyro radius and k = 0.5-4. Then, gross erosion profiles were calculated by a Monte Carlo micro-patterning and roughness (MPR) code for ion sputtering using as input the calculated azimuthal and polar IADs for each value of k . Good agreement with the experimental C deposition profiles was obtained for the case k = 2.5-3.5. This result is consistent with a previous kinetic modeling prediction of k ~ 3, as well as previous analytical investigations that predicted the L MPS to be several ion gyro radii. A validation of theoretical sheath models supports its applicability to ITER and pilot plant divertors to successfully predict plasma-materials interactions.

Erosion↗
DOE OSTI2021

Evidence of lithium mobility under neutron irradiation

Understanding the evolution of intermetallic materials in high-radiation environments is of great importance for fusion science and national security. Tritium ( 3 H) and lithium ( 6 Li, 7 Li) transport within neutron irradiated claddings coated with aluminide (FeAl3) has been investigated using state-of-the-art multimodal imaging. Specifically, scanning electron microscopy – focused ion beam (SEM-FIB) was used to prepare irradiated coating lift-out samples for follow-on microanalysis. Here, scanning transmission electron microscopy (STEM) was used to acquire atomic-scale information on the carbonaceous structure and elemental mapping. Atomic force microscopy (AFM) was used to determine lift-out dimensions nondestructively. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectral and depth profiling show unexpected lithium isotopic distributions in the irradiated cladding, raising an important evidence of possible light isotope mobility within the cladding under elevated temperature and irradiation. ToF-SIMS three-dimensional chemical mappings of mid- and bottom-cladding coatings show light isotopic (e.g., 3 H, 6 Li, 7 Li) distributions in the irradiated coating and give new insights into the fundamental mechanism related to transport mechanisms within the cladding. Multimodal imaging is power to link microstructure, chemistry, and nanoscale defects that impact reliability of these materials. Furthermore, chemical mapping offers observations of the microstructural evolution due to irradiation and provides insights into unexpected material transport under extreme conditions.

36 MATERIALS SCIENCE↗