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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Imaging Magnetometer

Imaging magnetometer proposed for scientific, industrial, or military use in detecting underground structures containing magnetic materials and underground machines generating and/or altering magnetic fields. Includes electron-beam tube integrated with phosphor-coated charge-coupled device (CCD). Images formed by magnetic deflection of electron beam. Locations, magnitudes, and directions of identifiable features of magnetic field examined to extract data on locations, sizes, and types of magnetically detected objects.

Moynihan, Philip I.↗
NASA NTRS2012

Comparison of Square and Radial Geometries for High Intensity Laser Power Beaming Receivers

In an effort to further advance a realizable form of wireless power transmission (WPT), high intensity laser power beaming (HILPB) has been developed for both space and terrestrial applications. Unique optical-to-electrical receivers are employed with near infrared (IR-A) continuous-wave (CW) semiconductor lasers to experimentally investigate the HILPB system. In this paper, parasitic feedback, uneven illumination and the implications of receiver array geometries are considered and experimental hardware results for HILPB are presented. The TEM00 Gaussian energy profile of the laser beam presents a challenge to the effectiveness of the receiver to perform efficient photoelectric conversion, due to the resulting non-uniform illumination of the photovoltaic cell arrays. In this investigation, the geometry of the receiver is considered as a technique to tailor the receiver design to accommodate the Gaussian beam profile, and in doing so it is demonstrated that such a methodology is successful in generating bulk receiver output power levels reaching 25 W from 7.2 sq cm of photovoltaic cells. These results are scalable, and may be realized by implementing receiver arraying and utilizing higher power source lasers to achieve a 1.0 sq m receiver capable of generating over 30 kW of electrical power. This type of system would enable long range optical "refueling" of electric platforms, such as MUAV s, airships, robotic exploration missions and provide power to spacecraft platforms which may utilize it to drive electric means of propulsion. In addition, a smaller HILPB receiver aperture size could be utilized to establish a robust optical communications link within environments containing high levels of background radiance, to achieve high signal to noise ratios.

Raible, Daniel E.↗
NASA NTRS1992

Formation and stability of polarization sheaths of a cross-field beam

A simple description is presented for a pure ion sheath formed on one side and a pure electron sheath formed on the other side of a neutral plasma beam. Both the ion and the electron sheath are found to be one-dimensionally stable and two-dimensionally unstable in a mode known as magnetron, slipping stream, and diocotron. This mode connects with the Kelvin-Helmholtz instability in neutral matter. The analytical results are confirmed both qualitatively and quantitatively by numerical simulations. The simulations help define the linear behavior of the long-wave instability generated in the electron (or ion) sheath, including a strong shear.

Cai, Dong S.↗
NASA NTRS1993

Timoshenko beam modeling for parameter estimation of NASA Mini-Mast truss

In this paper a distributed parameter model for the estimation of modal characteristics of NASA Mini-Mast truss is proposed. A closed-form solution of the Timoshenko beam equation, for a uniform cantilevered beam with two concentrated masses, is derived so that the procedure and the computational effort for the estimation of modal characteristics are improved. A maximum likelihood estimator for the Timoshenko beam model is also developed. The resulting estimates from test data by using Timoshenko beam model are found to be comparable to those derived from other approaches.

Shen, Ji Y.↗
DOE OSTI2023

Statistical Study of the Nonthermal Continuum Radiation Beaming Angle Measured by the High Frequency Receiver on Van Allen Probes-A

The nonthermal continuum (NTC) radiation beaming angle is computed over the entire Van Allen Probes-A mission when the spacecraft was in the dawn sector. The conditions in the dawn sector are favorable for the wave vector to lie near/in the spacecraft's spin plane allowing a favorable estimate of the beaming angle, and the dawn sector is also advantageous in that previous studies show NTC occurrence to peak in this sector. We found that scatter plots, over the entire mission, of beaming angle versus magnetic latitude form a distinct inverted-V pattern, with the apex at/near the magnetic equator. This pattern was sharpest for frequencies ( f ) ≲ 100 kHz. Using the NTC beaming formula from the linear mode conversion theory (LMCT), we show that such an inverted-V pattern is expected due to the large variation in the plasmapause location over the entire mission. The theoretical derived pattern qualitatively reproduces the observed pattern but not quantitatively. The lack of quantitative agreement is discussed and is attributed to several factors, one factor is off-centered emissions from the radio window. The qualitative agreement strongly supports LMCT as being the dominant mechanism generating NTC for f ≲ 100 kHz. For f ≳ 100 kHz, the inverted-V pattern becomes less distinct, and strong near-equatorial beaming is observed. Finally, after considering contamination of our selections by left-handed polarized AKR, our study suggests that besides LMCT another unidentified NTC generation mechanism becomes important for f ≳ 100 kHz.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2023

Statistical Study of the Non-Thermal Continuum Radiation Beaming Angle Measured By the High Frequency Receiver on Van Allen Probes-A

The nonthermal continuum (NTC) radiation beaming angle is computed over the entire Van Allen Probes-A mission when the spacecraft was in the dawn sector. The conditions in the dawn sector are favorable for the wave vector to lie near/in the spacecraft's spin plane allowing a favorable estimate of the beaming angle, and the dawn sector is also advantageous in that previous studies show NTC occurrence to peak in this sector. We found that scatter plots, over the entire mission, of beaming angle versus magnetic latitude form a distinct inverted-V pattern, with the apex at/near the magnetic equator. This pattern was sharpest for frequencies (f) ≲ 100 kHz. Using the NTC beaming formula from the linear mode conversion theory (LMCT), we show that such an inverted-V pattern is expected due to the large variation in the plasmapause location over the entire mission. The theoretical derived pattern qualitatively reproduces the observed pattern but not quantitatively. The lack of quantitative agreement is discussed and is attributed to several factors, one factor is off-centered emissions from the radio window. The qualitative agreement strongly supports LMCT as being the dominant mechanism generating NTC for f ≲ 100 kHz. For f ≳ 100 kHz, the inverted-V pattern becomes less distinct, and strong near-equatorial beaming is observed. After considering contamination of our selections by left-handed polarized AKR, our study suggests that besides LMCT another unidentified NTC generation mechanism becomes important for f ≳ 100 kHz.

Linear Mode Conversion Theory↗
NASA NTRS1995

Method for Fabricating Composite Structures Including Continuous Press Forming and Pultrusion Processing

A method for fabricating composite structures at a low-cost, moderate-to-high production rate is disclosed. A first embodiment of the method includes employing a continuous press forming fabrication process. A second embodiment of the method includes employing a pultrusion process for obtaining composite structures. The methods include coating yarns with matrix material, weaving the yarn into fabric to produce a continuous fabric supply, and feeding multiple layers of net-shaped fabrics having optimally oriented fibers into a debulking tool to form an undebulked preform. The continuous press forming fabrication process includes partially debulking the preform, cutting the partially debulked preform, and debulking the partially debulked preform to form a netshape. An electron-beam or similar technique then cures the structure. The pultrusion fabric process includes feeding the undebulked preform into a heated die and gradually debulking the undebulked preform. The undebulked preform in the heated die changes dimension until a desired cross-sectional dimension is achieved. This process further includes obtaining a net-shaped infiltrated uncured preform, cutting the uncured preform to a desired length, and electron-beam curing (or similar technique) the uncured preform. These fabrication methods produce superior structures formed at higher production rates, resulting in lower cost and high structural performance.

Farley, Gary L.↗
NASA NTRS1995

Heating and ionization of stellar chromospheres by nonthermal proton beams: Implications for impulsive phase, redshifted Lyman-alpha radiation in stellar flares

We investigate the physical basis for the timescale of impulsive-phase, redshifted Lyman-alpha emission in stellar flares on the assumption that it is determined by energy losses in a nonthermal proton beam that is penetrating the chromosphere from above. The temporal evolution of ionization and heating in representative model chromospheres subjected to such beams is calculated. The treatment of 'stopping' of beam protons takes into account their interactions with (1) electrons bound in neutral hydrogen, (2) nuclei of neutral hydrogen, (3) free electrons, and (4) ambient thermal protons. We find that, for constant incident beam flux, the system attains an equilibrium with the beam energy input to the chromosphere balanced by radiative losses. In equilibrium, the beam penetration depth is constant, and erosion of the chromosphere ceases. If the redshifted, impulsive-phase stellar flare Lyman-alpha emission is produced by downstreaming hydrogen formed through charge exchange between beam protons and ambient hydrogen, then the emission should end when the beam no longer reaches neutral hydrogen. The durations of representative emission events calculated on this assumption range from 0.1 to 14 s. The stronger the beam, the shorter the timescale over which the redshifted Lyman-alpha emission can be observed.

Brosius, Jeffrey W.↗
NASA NTRS1992

NPB Cesium Space Experiment

Neutral Particle Beam (NPB) weapons systems are planned to perform the ballistic missile defense functions of nuclear weapon/decoy discrimination and warhead kill at appropriate energy levels and ion currents. Negatively charged ions are produced in a specialized ion source and focused into a high quality particle beam. NPB linear accelerators accelerate and steer the negatively charged ions using electric and magnetic fields. After acceleration and steering the neutralizer system strips away extra electrons from ions to form the electrically neutral particle beam. The neutral beam then travels through space to the target unaffected by the Earth's magnetic fields. Continuing technological advances have greatly reduced the size and weight of NPB accelerator systems. Ion current production has been enhanced by over 100 percent with the intermittent addition of cesium at the NPB ion source device. This increase in current is essential to attain the most light weight, compact NPB platforms and minimize expensive launch costs. Addition of cesium into the ion source has been identified by the NPB community as the highest priority risk reduction space experiment necessary prior to planned NPB accelerator experiments and later weapons systems. The NPB Cesium Space Experiment is planned to successfully demonstrate controlled cesium introduction and vaporization into a simulated ion source chamber. Microgravity effects on the cesium deposition will be studied as will the effects of small amounts of cesium on high voltage accelerator components that might be susceptible to electrical insulator break downs. The experiment design will simulate as closely as possible the environment, physical and operational characteristics of the actual NPB ion source.

Parsons, George M., III↗
DOE OSTI2022

GaN vertical-channel junction field-effect transistors with regrown p-GaN by metal organic chemical vapor deposition (MOCVD)

Fabricating a vertical-channel junction field-effect transistor includes forming an unintentionally doped GaN layer on a bulk GaN layer by metalorganic chemical vapor deposition, forming a Cr/SiO 2 hard mask on the unintentionally doped GaN layer, patterning a fin by electron beam lithography, defining the Cr and SiO 2 hard masks by reactive ion etching, improving a regrowth surface with inductively coupled plasma etching, removing hard mask residuals, regrowing a p-GaN layer, selectively etching the p-GaN layer, forming gate electrodes by electron beam evaporation, and forming source and drain electrodes by electron beam evaporation. The resulting vertical-channel junction field-effect transistor includes a doped GaN layer, an unintentionally doped GaN layer on the doped GaN layer, and a p-GaN regrowth layer on the unintentionally doped GaN layer. Portions of the p-GaN regrowth layer are separated by a vertical channel of the unintentionally doped GaN layer.

Zhao, Yuji↗
DOE OSTI2023

Improving Longitudinal Impedance of Inductive Inserts

Space charge compensation is essential to keeping the beam inside a ring such as PSR in the desired bunch form. The space charges of the ring will lead to the beam debunching, and the most prominent form of compensation for this is the use of RF to bunch the ring back. It has long been known however, that the impedance presented to the beam by its space charge could be compensated by a passive component. Such a passive component has been in use in PSR since 2000, but upgrading it could greatly improve the capabilities of the PSR. Additionally, the inserts presently used would require updating to match any changes in the beam pipe, both mechanically and to increase the space charge compensation.

43 PARTICLE ACCELERATORS↗
NASA NTRS2017

Computationally Efficient Beam Elements for Accurate Stresses in Sandwich Laminates and Laminated Composites with Delaminations

Laminated composites are prone to delamination failure due to the lack of reinforcement through the thickness. Therefore, during the design process the initiation and propagation of delaminations should be accounted for as early as possible. This paper presents computationally efficient nine degree-of-freedom (dof) and eight-dof shear locking-free beam elements using the mixed form of the refined zigzag theory (RZT(sup(m))). The corresponding nine-dof and eight-dof elements use the anisoparametric and constrained anisoparametric interpolation schemes, respectively, to eliminate shear locking in slender beams. The advantage of the present element over previous RZT beam elements is that no post-processing is required to accurately model the transverse shear stress while maintaining the computational efficiency of a low-order beam element. Comparisons with high-fidelity finite element models and three-dimensional elasticity solutions show that the elements can robustly and accurately predict the displacement field, axial stress and transverse shear stress through the thickness of a sandwich beam or a composite laminate with an embedded delamination. In fact, the accuracy and computational efficiency of predicting stresses in laminates with embedded delaminations make the present elements attractive choices for RZT-based delamination initiation and propagation methodologies available in the literature.

R. M. J. Groh↗
DOE OSTI2025

A data-driven method to estimate the antiproton background in the Mu2e experiment

The Mu2e experiment at Fermilab will search for the Charged Lepton Flavour Violating (CLFV) process of coherent, neutrinoless µ− → e − conversion in the field of an aluminum nucleus. The expected signal is a monochromatic electron with the energy of 104.97 MeV, slightly below the muon rest mass. Observation of a CLFV process would provide unambiguous evidence for Beyond the Standard Model (BSM) physics. Mu2e is sensitive to a wide range of BSM models and has the capability to distinguish between them, guiding us towards the most accurate models. The key features of the Mu2e experiment are: (1) a high intensity pulsed negative muon beam with about 1010 stopped µ −/s, and (2) a sophisticated superconducting solenoid system with a gradient magnetic field to form and guide the intense muon beam to the target. The Mu2e physics data taking is expected to begin in 2027. For Run I, the expected 5σ discovery sensitivity is Rµe = 1.2 × 10−15, with a total expected background of 0.11 ± 0.03 events. In the absence of a signal, the expected upper limit is Rµe < 6.2 × 10−16 at 90% CL. The success of this experiment hinges on the accurate estimation of the background from various SM processes that could provide signal-like electrons. One of the background processes is antiprotons annihilating in the stopping target to produce signal like electrons through π0 → γγ decays followed by γ conversions, and π− → µ−ν¯ decays followed by µ− decay. It is a relatively small background with large uncertainty (100%) due to the lack of antiproton production cross section information for the Mu2e proton beam energy of 8 GeV. We have developed a novel methodology to estimate the antiproton background in-situ. This forms the main theme of the thesis. We observed that at Mu2e energies, antiproton annihilation in the stopping target is the only source of events with multiple, simultaneous particle trajectories. From Geant4 simulations, only about 0.2% of the simulated antiproton annihilation events have a signal-like electron. Meanwhile, ∼ 5% of events have multiple reconstructible particle tracks per event. Therefore, we have devised a methodology to reconstruct the multi-track events and estimate the antiproton background by exploiting the large ratio of the production rates of the two final states.

Chithirasreemadam, Namitha [Pisa U.] (ORCID:000000↗
DOE OSTI2023

Design of Electrostatic Aberration Correctors for Scanning Transmission Electron Microscopy

Abstract In a scanning transmission electron microscope (STEM), producing a high-resolution image generally requires an electron beam focused to the smallest point possible. However, the magnetic lenses used to focus the beam are unavoidably imperfect, introducing aberrations that limit resolution. Modern STEMs overcome this by using hardware aberration correctors comprised of many multipole elements, but these devices are complex, expensive, and can be difficult to tune. We demonstrate a design for an electrostatic phase plate that can act as an aberration corrector. The corrector is comprised of annular segments, each of which is an independent two-terminal device that can apply a constant or ramped phase shift to a portion of the electron beam. We show the improvement in image resolution using an electrostatic corrector. Engineering criteria impose that much of the beam within the probe-forming aperture be blocked by support bars, leading to large probe tails for the corrected probe that sample the specimen beyond the central lobe. We also show how this device can be used to create other STEM beam profiles such as vortex beams and probes with a high degree of phase diversity, which improve information transfer in ptychographic reconstructions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Beam power scale-up in micro-electromechanical systems based multi-beam ion accelerators

We report on the development of multi-beam RF linear ion accelerators that are formed from stacks of low cost wafers and describe the status of beam power scale-up using an array of 120 beams. The total argon ion current extracted from the 120-beamlet extraction column was 0.5 mA. The measured energy gain in each RF gap reached as high as 7.25 keV. We present a path of using this technology to achieve ion currents >1 mA and ion energies >100 keV for applications in materials processing.

47 OTHER INSTRUMENTATION↗
NASA NTRS1985

The effect of Low Earth Orbit space environment on polymeric spacecraft materials

The Advanced Composite Materials Exposure to Space Experiment flown on shuttle mission STS-41G was designed to investigate the effect of low Earth orbit space environment on polymeric spacecraft materials. The effect of the phenomenon attributed to atomic oxygen on Kapton and advanced composite materials of carbon-epoxy and kevlar epoxy is described. The results of true space exposure are compared to duplicate specimens subjected to a simulated environment in an Earth-based nozzle beam test facility utilizing microwave discharge to form atomic oxygen. Although the energy level for atomic oxygen in the beam facility did not achieve the orbital energy level of 5 eV, similar effects of surface erosion and degradation are observed after equivalent exposure times.

Zimcik, D. G.↗
NASA NTRS1997

A Higher-Order Bending Theory for Laminated Composite and Sandwich Beams

A higher-order bending theory is derived for laminated composite and sandwich beams. This is accomplished by assuming a special form for the axial and transverse displacement expansions. An independent expansion is also assumed for the transverse normal stress. Appropriate shear correction factors based on energy considerations are used to adjust the shear stiffness. A set of transverse normal correction factors is introduced, leading to significant improvements in the transverse normal strain and stress for laminated composite and sandwich beams. A closed-form solution to the cylindrical elasticity solutions for a wide range of beam aspect ratios and commonly used material systems. Accurate shear stresses for a wide range of laminates, including the challenging unsymmetric composite and sandwich laminates, are obtained using an original corrected integration scheme. For application of the theory to a wider range of problems, guidelines for finite element approximations are presented.

Cook, Geoffrey M.↗