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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
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NASA NTRS1981

Proton-induced noise in digicons

The Space Telescope, which carries four Digicons, will pass several times per day through a low-altitude portion of the radiation belt called the South Atlantic Anomaly. This is expected to create interference in what is otherwise anticipated to be a noise-free device. Two essential components of the Digicon, the semiconductor diode array and the UV transmitting window, generate noise when subjected to medium-energy proton radiation, a primary component of the belt. These trapped protons, having energies ranging from 2 to 400 Mev and fluences at the Digicon up to 4,000 P+/sec-sq cm, pass through both the window and the diode array, depositing energy in each. In order to evaluate the effect of these protons, engineering test models of Digicon tubes to be flown on the High Resolution Spectrograph were irradiated with low-flux monoenergetic proton beams at the University of Maryland cyclotron. Electron-hole pairs produced by the protons passing through the diodes or the surrounding bulk caused a background count rate. This is the result of holes diffusing over a distance of many diode spacings, causing counts to be triggered simultaneously in the output circuits of several adjacent diodes. Pulse-height spectra of these proton-induced counts indicate that most of the bulk-related counts overlap the single photoelectron peak. A geometrical model will be presented of the charge collection characteristics of the diode array that accounts for most of the observed effects.

Smith, L. C.↗
NASA NTRS1983

Electron microscopic observations of hydrogen implantation in ilmenites

Hydrogen ion beams were found to form submicrometer, bumpy textures on the surface of ilmenite grains. From this effect, it is believed that similar bumpy textures seen on lunar ilmenite, pyroxene, and olivine grains are likely to be caused by solar wind irradiation. As a consequence, the concentration of bumpy textured grains may be a useful index of surface maturity for lunar soils. An attempt was made to search for grains with these bumpy textures in interplanetary dust and lunar and meteoritic regolith breccias in order to obtain information about the duration of their exposure to the solar wind. Solar wind irradiation was simulated on natural, terrestrial ilmenite. Hydrogen ion beams were directed at small grains and polished sections which were then examined by electron microscopy.

Blanford, G. E.↗
NASA NTRS1986

The effects of radiation on the interlaminar fracture toughness of a graphite/epoxy composite

An experimental study is made of the effect of electron irradiation (10 to the 10th rad), simulating a 30-year geosynchronous orbit exposure, on the fracture toughness of a graphite/epoxy composite, T300/934. The double cantilever beam (DBC) test is used to determine Mode I (peel) critical strain energy release rate and the edge delamination tension (EDT) test is used to determine mixed Mode I and II (peel and shear) critical strain energy release rate. It is found that the electron interaction of the epoxy matrix material enhances the fracture toughness properties of the composite and that the test temperature has a significant effect on the fracture toughness of both baseline and irradiated material.

Funk, J. G.↗
NASA NTRS1973

High-energy electron-beam deposition onto a hot graphite surface.

The momentum transfer and blow-off vapor yield resulting from the deposition of a pulsed high-power electron beam onto a plane graphite target with surface temperatures of 300 K and 5000 K are examined experimentally. The results show that with identical electron beams the momentum transfer and vapor yield are between two and three times larger when irradiating the 5000 K surface as compared with the 300 K surface.

Robin, J. E.↗
NASA NTRS1995

Effects of low earth orbit on the optical performance of multi-layer enhanced high reflectance mirrors

Two mirror designs developed for space applications were flown along with a standard mid-infrared design on the leading and trailing edges of the Long Duration Exposure Facility (LDEF). Preliminary observations of induced changes in optical performance of ZnS-coated mirrors and impact-related microstructural and microchemical effects are described in the proceedings of the First LDEF Post-Retrieval Symposium. In this paper, effects of the induced environment and meteoroid/debris impacts on mirror performance are described in more detail. Also, an analysis of reflectance spectra using the results of Auger and secondary ion mass spectroscopy (SIMS) profiling measurements are used to identify an optical-degradation mechanism for the ZnS-coated mirrors. Structural damage associated with a high-velocity impact on a (Si/Al2O3)-coated mirror was imaged optically and with scanning electron and atomic force microscopy (SEM and AFM). Scanning Auger and SIMS analysis provided chemical mapping of selected impact sites. The impact data suggest design and fabrication modifications for obtaining improved mechanical performance using a design variation identified in preflight laboratory simulations. Auger surface profile and SIMS imaging data verified the conclusion that secondary impacts are the source of contamination associated with the dendrites grown on the leading-edge ZnS-coated test samples. It was also found that dendrites can be grown in the laboratory by irradiating contaminated sites on a trailing-edge ZnS-coated sample with a rastered electron beam. These results suggest a mechanism for dendrite growth.

Donovan, Terence↗
NASA NTRS2004

Electron Irradiation Effects on Nanocrystal Quantum Dots Used in Bio-Sensing Applications

Effects of electron irradiation on some of the optical properties in organic CdSe nanocrystals coated in trioctylphosphine oxide (TOPO) and biologically compatible CdSe nanocrystals coated in mercaptoacetic acid, as CdSe as CdSe nanocrystals conjugated with the protein are investigated using the technique of cathodoluminescence. Effects of varying the beam energy and temperatures were examined and faster degradation at cryogenic temperatures and higher beam energies was found under some conditions.

nanocrystal↗
NASA NTRSDate not supplied

Unraveling Solar Wind Space Weathering of Carbon-Rich Asterods: Low-Flux VS. High-Flux Ion Irradiation of Murchison

Introduction: Space weathering processesalter the microstructural, compositional, and optical properties of airless planetary surfaces.Solar wind space weatheringforms ion-damaged rims within the outermost ~100 nm of regolith grains through atomic-displacements and implantation of energetic H+and He+ions[1]. Transmission electron microscope(TEM)studies of space weathered Itokawa and lunar olivine particles reveal predominantly nanocrystalline solar wind-damaged rims with only minor regions of amorphization[2-5]. This finding differs from laboratoryion irradiation experiments in which samples become amorphous at fluences 2-3 orders of magnitude lower than the independentlyconstrained fluences for still-crystalline natural samples [6-7].Ion flux is generally considered to have a secondaryeffectcompared to fluence in these irradiation experiments. However, solar wind irradiation of natural samples occurs at a flux that is ~4-5 orders of magnitude lower than whatisused inlaboratory simulations (e.g., [6,8-9]). Constraining how the very low ion flux of solar wind influences the microstructural, chemical, and spectral alteration of silicate minerals will improve our understanding of solar wind space weathering and aid in the analysis of returned samples from the Hayabusa2 and OSIRIS-REx missions. Here we report results from low-and high-flux ion irradiation experiments on the Murchison (CM2)meteoritewithcomparable total fluences. Methods: We performed low-flux and high-flux He+(4 keV) and H+(1 keV) irradiation experiments on separate, dry-cut Murchison slabs. Low-flux He+irradiation reached a total fluence of 2.1 x 1016ions/cm2(~400 years of exposure at Bennu) using a flux of 3.6 x 1011ions/cm2/s; low-flux H+irradiation reached a total fluence of 3.9 x 1016ions/cm2(~30 years) using a flux of 6.6 x 1011ions/cm2/s. High-flux He+irradiation reached a total fluence of 2.0 x 1016ions/cm2(~400 years)using a flux of 9.1 x 1012ions/cm2/s; high-flux H+irradiation reached a total fluence of 5.8 x 1016ions/cm2(~50 years)using flux of 8.4 x 1012ions/cm2/s. By irradiating to similar total fluences in both the low-flux and high-flux experiments, we can better isolate and evaluatethe effects of ion flux. Differences between unirradiatedand irradiated surfaces are determined using threeanalytical techniques:(1) in situX-ray photoelectron spectroscopy(XPS) reveals changes in surface chemistry,(2) visible to near-infrared spectroscopy (VNIR; 0.35-2.5 μm) highlights changes in spectraltrends, such as albedo and slope, and (3) TEM and energy-dispersive X-ray spectroscopy (EDS) identifieschanges in nanoscale structure and elemental composition within olivine and matrix electron-transparent thin sections prepared using focused ion beam scanning electron microscopy (FIB-SEM). Results and Discussion: XPS analyses of the low-fluxand high-fluxHe+-and H+-irradiated samples showa minorreduction in surface carbon contentand chemicalreduction ofFe3+to Fe2+. The latter result is consistent with the higher Fe2+/Fe3+ratios observed in phyllosilicate-rich space weathered rims of Ryugu grains [10].VNIR analyses suggest that the low-flux H+-irradiated spectrum has a slightly bluer slope (over 0.65-2.5 μm) compared to the unirradiated VNIR spectrum from [9] while the low-flux He+-irradiated spectral slope is comparable to the unirradiated surface. Both the high-flux He+-and H+-irradiated VNIR spectra exhibitslightlyhigheralbedos at shorter wavelengths relativeto their unirradiated counterparts, with He+irradiation yielding a greater change. Thus far, the low-flux He+-irradiated matrix and olivine FIBsections as well as the low-flux H+-irradiated olivine FIBsection have been examined with TEM. The surfaces of all three samplesshowless vesiculation than high-flux/high-fluenceirradiated matrix and olivine samples from [9]. The depth of phyllosilicate amorphization in thelow-fluxHe+-irradiated matrix FIBsection varieslaterally, with crystalline domains occurring as shallow as ~25 nm in some regions. Thelow-flux He+-irradiated olivine FIBsection has acontinuous,~40-90 nm thick ion-affected layer with polycrystalline and amorphous microstructures. The low-flux H+-irradiated olivine sampleexhibits a distinct, ~10-40 nm ion-affected layer whose uppermost ~20 nmin thicker regions is predominantly amorphous.Continuing to compare results from this work to those from [9] will provide a comprehensive understanding of how ion flux impacts the microstructural, chemical, and optical modification of various mineral phases and, in turn,help identify space weathering features from parent body alteration in Hayabusa2 and OSIRIS-REx returned samples.

D L Laczniak↗
NASA NTRS2023

Investigating the Role of Incident Ion Flux in Solar Wind Space Weathering of Carbon-Rich Asteroidal Regolith Via H+ and He+ Irradiation of the Murchison Meteorite

We present results from a set of low and high flux 1 keV/amu H + and He + irradiation experiments performed on slabs of the Murchison CM2 carbonaceous chondrite. The low flux conditions for H + and He + irradiation were ~1-1.5 orders of magnitude lower than the high flux conditions, and each experiment was irradiated to a total fluence between ~3 × 10 16 to ~6 × 10 16 ions/cm 2 . Irradiation-induced changes in the surface chemistry and optical properties of the Murchison samples were evaluated using in situ X-ray photoelectron spectroscopy (XPS) and visible and near-infrared spectroscopy (VNIR). We characterized the microstructure and composition of ion damaged rims in focused ion beam (FIB) cross-sections extracted from olivine and matrix material in each irradiated Murchison slab using transmission electron microscopy (TEM). XPS results suggest that both low flux and high flux H + and He + irradiation cause minor sputtering of surface carbon as well as a reduction in the valence state of iron, from Fe 3+ to Fe 2+ . Slope bluing is observed in VNIR spectra of the irradiated samples which may reflect carbonization and dehydrogenation of organic species and contrasts with reddening trends associated with npFe 0 formation. Although we do not observe a strong flux-dependence on the crystallinity of ion-damaged olivine, TEM analyses reveal a variety of microstructures in all olivine FIB-sections, suggesting that crystallographic orientation affects amorphization efficiency. Analyses of matrix FIB-sections indicate that phyllosilicate alteration is mainly driven by He+ irradiation, where the higher incident flux leads to greater amorphization and the formation of more distinct ion-damaged layers, similar to smooth layers in returned Ryugu particles. TEM results also provide some evidence that higher ion flux leads to greater vesiculation, with He + irradiation being more efficient at vesiculation than H + irradiation, and that higher ion flux may promote the segregation of Mg and Si into laterally extensive lenses and layers in olivine samples. We discuss the implications of these findings for constraining the role that ion flux plays in the development of space weathering characteristics in silicate phases present in carbonaceous asteroidal regoliths. These results will be important for understanding the complexity of this process and how it operates on carbon-rich airless bodies like asteroids Bennu and Ryugu.

meteorites↗
NASA NTRS1983

Enhanced adhesion from high energy ion irradiation

It has been found that the adhesion of thin metal films on insulators, semiconductors, and metals could be improved by subjecting the material to a high-energy ion bombardment. Griffith et al. (1982) have first suggested a use of this technique with insulators. The present investigation has the objective to determine the mechanism for the adhesion enhancement. A description is presented of a preliminary transmission electron microscopy (TEM) study of thinned bonded samples of silver on silicon using electron diffraction. It is found that irradiation of a variety of thin film-substrate combinations by heavy ion beams will provide a remarkable improvement in the adherence of the film. The evidence for the mechanism involved in the enhancement of adhesion is discussed.

Werner, B. T.↗
NASA NTRS1990

Some optical and electron microscope comparative studies of excimer laser-assisted and nonassisted molecular-beam epitaxically grown thin GaAs films on Si

The quality of GaAs thin films grown via MBE under pulsed excimer laser irradiation on Si substrates is examined in both laser-irradiated and nonirradiated areas using Raman scattering, Rayleigh scattering, and by photoluminescence (PL), as a function of temperature, and by TEM. The temperature dependence of the PL and Raman peak positions indicates the presence of compressive stress in the thin GaAs films in both laser-irradiated and nonirradiated areas. This indicates incomplete homogeneous strain relaxation by dislocations at the growth temperature. The residual compressive strain at the growth temperature is large enough such that even with the introduction of tensile strain arising from the difference in thermal expansion coefficients of GaAs and Si, a compressive strain is still present at room temperature for these thin GaAs/Si films.

Lao, Pudong↗
NASA NTRS1977

Materials and techniques for spacecraft static charge control

An overview of the design, development, fabrication, and testing of transparent conductive coatings and conductive lattices deposited or formed on high resistivity spacecraft dielectric materials to obtain control static charge buildup on spacecraft external surfaces is presented. Fabrication techniques for the deposition of indium/tin oxide coatings and copper grid networks on Kapton and FEP Teflon films and special frit coatings for OSR and solar cell cover glasses are discussed. The techniques include sputtering, photoetching, silkscreening, and mechanical processes. A facility designed and built to simulate the electron plasma at geosynchronous altitudes is described along with test procedures. The results of material characterizations as well as electron irradiation aging effects in this facility for spacecraft polymers treated to control static charge are presented. The data presents results for electron beam energies up to 30 kV and electron current densities of 30 nA/cm squared. Parameters measured include secondary emission, surface leakage, and through the sample currents as a function of primary beam energy and voltage.

Amore, L. J.↗
NASA NTRS1981

Two-dimensiosnal electron beam charging model for polymer films

A two dimensional model was developed to describe the charging of thin polymer films exposed to a uniform mon-energetic electron beam. The study was motivated by observed anomalous behavior of geosynchronous satellites which was attributed to electrical discharges associated with the differential charging of satellite surfaces of magnetospheric electrons. Electric fields both internal and external to the irradiated specimen were calculated at steady state in order to identify regions of high electrical stress. Particular emphasis was placed on evaluating the charging characteristics near the material's edge. The model was used to identify and quantify the effects of some of the experimental parameters notably: beam energy; beam angle of incidence; beam current density; material thickness; and material width. Simulations of the following situations were also conducted: positive or negative precharging over part of the surface; a central gap in the material; and a discontinuity in the material's thickness.

Reeves, R. D.↗
NASA NTRS1990

Electron-impact ionization and electron attachment cross sections of radicals important in transient gaseous discharges

Electron-impact ionization and electron attachment cross sections of radicals and excited molecules were measured using an apparatus that consists of an electron beam, a molecular beam and a laser beam. The information obtained is needed for the pulse power applications in the areas of high power gaseous discharge switches, high energy lasers, particle beam experiments, and electromagnetic pulse systems. The basic data needed for the development of optically-controlled discharge switches were also investigated. Transient current pulses induced by laser irradiation of discharge media were observed and applied for the study of electron-molecule reaction kinetics in gaseous discharges.

Lee, Long C.↗
NASA NTRS1992

Electron spectroscopy analysis

The Surface Science Laboratories at the University of Alabama in Huntsville (UAH) are equipped with x-ray photoelectron spectroscopy (XPS or ESCA) and Auger electron spectroscopy (AES) facilities. These techniques provide information from the uppermost atomic layers of a sample, and are thus truly surface sensitive. XPS provides both elemental and chemical state information without restriction on the type of material that can be analyzed. The sample is placed into an ultra high vacuum (UHV) chamber and irradiated with x-rays which cause the ejection of photoelectrons from the sample surface. Since x-rays do not normally cause charging problems or beam damage, XPS is applicable to a wide range of samples including metals, polymers, catalysts, and fibers. AES uses a beam of high energy electrons as a surface probe. Following electronic rearrangements within excited atoms by this probe, Auger electrons characteristic of each element present are emitted from the sample. The main advantage of electron induced AES is that the electron beam can be focused down to a small diameter and localized analysis can be carried out. On the rastering of this beam synchronously with a video display using established scanning electron microscopy techniques, physical images and chemical distribution maps of the surface can be produced. Thus very small features, such as electronic circuit elements or corrosion pits in metals, can be investigated. Facilities are available on both XPS and AES instruments for depth-profiling of materials, using a beam of argon ions to sputter away consecutive layers of material to reveal sub-surface (and even semi-bulk) analyses.

Gregory, John C.↗
NASA NTRS1977

SEM analysis of ionizing radiation effects in linear integrated circuits

A successful diagnostic technique was developed using a scanning electron microscope (SEM) as a precision tool to determine ionization effects in integrated circuits. Previous SEM methods radiated the entire semiconductor chip or major areas. The large area exposure methods do not reveal the exact components which are sensitive to radiation. To locate these sensitive components a new method was developed, which consisted in successively irradiating selected components on the device chip with equal doses of electrons /10 to the 6th rad (Si)/, while the whole device was subjected to representative bias conditions. A suitable device parameter was measured in situ after each successive irradiation with the beam off.

Stanley, A. G.↗
NASA NTRS2005

Laboratory Astrophysics Using a Microcalorimeter and Bragg Crystal Spectrometer on an Electron Beam Ion Trap

We completed modifications to the new microcalorimeter system dedicated for use on the EBIT at NIST, which included: 1) a redesign of the x-ray calibration source from a direct electron impact source to one that irradiates the microcalorimeter with fluorescent x-rays. The resulting calibration lines are free of bremsstrahlung background; 2) the microcalorimeter electronic circuit was significantly improved to ensure long-term stability for lengthy experimental runs

Brinton, John↗
NASA NTRS1982

Science on the Space Shuttle

On the Space Shuttle's third flight, scientific instruments will study the electromagnetic environment with charging and electron beams. Beam plasma discharge will be studied. The plasma diagnostics package contains electromagnetic and particle sensors to study the ionosphere. An attempt will be made to establish a more accurate base of solar UV irradiance measurements with an absolute error of 10 percent or less over the wavelength region 120-400 nm. The solar flare X-ray polarimeter will observe flare X-rays emitted between 5 and 30 keV and measure their polarization as a function of time and photon energy. A photopolarimeter will help study zodiacal light, and interplanetary dust will be sampled by a section of thick aluminum foil. Plant seedlings will be grown to research the effect of near-zero gravity on lignification. A thermal canister experiment will help determine whether instruments can be maintained at a fixed temperature under varying thermal loads.

Neupert, W. M.↗
NASA NTRS1991

Evaluation of the minority carrier diffusion length and surface-recombination velocity in GaAs p/n solar cells

The minority carrier diffusion length (Lp) and the surface recombination velocity (Vs) were measured as a function of distance (x) from the p-n junction in GaAs p/n concentrator solar cells. The measured Vs values were used in a theoretical expression for the normalized electron-beam-induced current. A fitting procedure was then used to fit this expression with experimental values to obtain Lp. The results show that both Vs and Lp vary with x. Lp measured in irradiated cells showed a marked reduction. These values were compared to those measured previously which did not account for Vs.

Hakimzadeh, Roshanak↗