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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Electron Beam Freeform Fabrication for Cost Effective Near-Net Shape Manufacturing

Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cm3/hr (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

Taminger, Karen M.↗
DOE OSTI2022

Niobium to Titanium Electron Beam Welding for SRF Cavities

Titanium and niobium are the main materials used for the fabrication of Superconducting Radio Frequency (SRF) cavities. These two metals are usually joined , using various welding techniques, using a third material in between. This contribution focuses on the development of an innovative electron beam welding technique capable of producing a strong bond between these two different materials. Several samples are produced and tested to assess the mechanical strength at room and cryogenic temperature as well as the composition of the resulting welded joint. Also, the first units of the Single Spoke Resonator type 2 (SSR2) cavities for the Proton Improvement Plan-II (PIP-II [1]) have been fabricated joining directly various grades of titanium to niobium and results gathered through the fabrication will be reported.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Optimize Electron Beam Energy toward In Situ Imaging of Thick Frozen Bio-Samples with Nanometer Resolution Using MeV-STEM

To optimize electron energy for in situ imaging of large biological samples up to 10 μm in thickness with nanoscale resolutions, we implemented an analytical model based on elastic and inelastic characteristic angles. This model has been benchmarked by Monte Carlo simulations and can be used to predict the transverse beam size broadening as a function of electron energy while the probe beam traverses through the sample. As a result, the optimal choice of the electron beam energy can be realized. In addition, the impact of the dose-limited resolution was analysed. While the sample thickness is less than 10 μm, there exists an optimal electron beam energy below 10 MeV regarding a specific sample thickness. However, for samples thicker than 10 μm, the optimal beam energy is 10 MeV or higher depending on the sample thickness, and the ultimate resolution could become worse with the increase in the sample thickness. Moreover, a MeV-STEM column based on a two-stage lens system can be applied to reduce the beam size from one micron at aperture to one nanometre at the sample with the energy tuning range from 3 to 10 MeV. In conjunction with the state-of-the-art ultralow emittance electron source that we recently implemented, the maximum size of an electron beam when it traverses through an up to 10 μm thick bio-sample can be kept less than 10 nm . This is a critical step toward the in situ imaging of large, thick biological samples with nanometer resolution.

36 MATERIALS SCIENCE↗
NASA NTRS2006

Electron Beam Freeform Fabrication (EBF3) for Cost Effective Near-Net Shape Manufacturing

Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley Research Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF3), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. EBF3 deposits of 2219 aluminium and Ti-6Al-4V have exhibited a range of grain morphologies depending upon the deposition parameters. These materials have exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 2500 cubic centimeters per hour (150 in3/hr) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

Taminger, Karen M.↗
DOE OSTI2023

Understanding the Effect of Electron Beam Melting Scanning Strategies on the Aluminum Content and Materials State of Single Ti-6Al-4V Feedstock

Research on the additive manufacturing of metals often neglects any characterization of the composition of final parts, erroneously assuming a compositional homogeneity that matches the feedstock material. Here, the composition of electron-beam-melted Ti-6Al-4V produced through three distinct scanning strategies (linear raster and two point melting strategies, random fill and Dehoff fill) is characterized both locally and globally through energy-dispersive spectroscopy and quantitative chemical analysis. As a result of the different scanning strategies used, differing levels of preferential vaporization occur across the various parts, leading to distinct final compositions, with extremes of ~5.8 wt.% Al and ~4.8 wt.% Al. In addition, energy-dispersive spectroscopy composition maps reveal specific features in both the XY and XZ planes (with Z being the build direction) as a result of local inhomogeneous preferential vaporization. The subsequent change in composition significantly modifies the materials’ state of parts, wherein parts and local regions with higher aluminum contents lead to higher hardness levels (with a ~50 HV difference) and elastic property values and vice versa. While varying scan strategies and scan parameters are known to modify the microstructure and properties of a part, the effect on composition cannot, and should not, be neglected.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Quantification of the effects of generation volume, surface recombination velocity, and diffusion length on the electron-beam-induced current and its derivative Determination of diffusion lengths in the low micron and submicron ranges

A systematic and quantitative analysis is carried out to investigate the effects of the shape (point, cube, Gaussian) and size of the generation volume, the surface recombination velocity, and the diffusion length on the electron-beam-induced current (EBIC) and its derivative (DEIC). Thick homogeneously doped samples exhibiting diffusion lengths in the low micron and submicron range are considered. The results are presented in computed EBIC curves as a function of scanning distance and of the ratio true diffusion length/effective diffusion length. Shown using these curves are: (1) a simple and yet rigorous method for the determination of the true diffusion length, taking into consideration all of the factors cited above, (2) a method for the rapid determination of the surface recombination velocity, (3) the condition under which the source shape becomes insignificant, and (4) a new value for the lower limit of the diffusion length which can be determined by the EBOC technique.

Luke, K. L.↗
DOE OSTI2021

Texture evolution as a function of scan strategy and build height in electron beam melted Ti-6Al-4V

Metal additive manufacturing (AM) enables customizable, on-demand parts, allowing for new designs and improved engineering performance. Yet, the ability to control AM metal alloy microstructures (i.e., grain morphology, crystallographic texture, and phase content) is lacking. Furthermore, this work performs corroborative neutron diffraction and large-scale electron backscatter diffraction (EBSD) measurements to assess crystallographic texture in electron beam melted (EBM) Ti-6Al-4V as a function of scan strategy and build height. Texture components for one raster and two spot melt scan strategies were evaluated using a triclinic specimen symmetry to capture all possible texture components, which were found to be considerably different than previously reported values from studies employing orthotropic specimen symmetry. This finding highlights the importance of a standard method and best practice for assessing textures produced by AM.

36 MATERIALS SCIENCE↗
NASA NTRS1981

Experimental validation of a numerical model predicting the charging characteristics of Teflon and Kapton under electron beam irradiation

The effect differential charging of spacecraft thermal control surfaces is assessed by studying the dynamics of the charging process. A program to experimentally validate a computer model of the charging process was established. Time resolved measurements of the surface potential were obtained for samples of Kapton and Teflon irradiated with a monoenergetic electron beam. Results indicate that the computer model and experimental measurements agree well and that for Teflon, secondary emission is the governing factor. Experimental data indicate that bulk conductivities play a significant role in the charging of Kapton.

Hazelton, R. C.↗
DOE OSTI2024

Tuning Surface Adhesion Using Grayscale Electron-beam Lithography

Surface texturing of manufactured products tailors their properties, such as friction, adhesion, biocompatibility, or fluid interactions. However, advancements in this area are largely the result of trial-and-effort testing and generally lack a science-guided framework for determining the surface topography that will optimize performance. The present investigation explores grayscale electron-beam lithography as a means to create multiscale surface patterns to control surface performance. Here, we created and characterized a set of surface textures on a silicon wafer; the textures were superpositions of sine waves of varying wavelengths and amplitudes. First, the multiscale topography of the patterned surface was characterized, using profilometry and atomic force microscopy, to understand its fidelity to the designed-in pattern. The results of this analysis demonstrated how grayscale lithography accurately controlled the lateral size of features but was less precise on the vertical height of the surface, and also introduced inherent roughness below the scale of patterning. Second, a micromechanical tester was used to characterize the adhesion of the surfaces with large-scale polished silicon spheres. The results showed that adhesion could be tailored, with significant contribution from all of the designed-in length scales of topography. The strength of adhesion did not correlate with conventional roughness parameters but could be accurately modeled using simple numerical integration. Taken together, this investigation demonstrates the promise and challenges of grayscale e-beam lithography with multiscale patterns as a method for the tailoring of surface performance.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Microstructure and 77K mechanical properties of electron beam welded Cu101- Inconel 625 joints

In developing large-scale next-generation superconducting radio frequency (SRF) linear accelerators using superconducting films on Cu, the design and development of dissimilar welding and joining metals, such as Cu to Inconel, stainless steel, and Nb, are essential. In this talk, we present the development of procedures for electron-beam welding of Cu¿Inconel 625 and evaluation of the microstructure and 77K mechanical properties of the weld and base material in the welded condition and heat treatments in the 750°C ¿950°C heat treatment range. The results will be presented in the context of developing joining techniques for low-temperature applications where high conductivity and strength, vacuum hygiene, and magnetic properties of the material need consideration. The methods presented here are being deployed to thin film SRF Cu cavities at Jefferson Lab. Acknowledgment: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear

Khanal, Bashu↗
DOE OSTI2026

Laboratory tests of laser control of electron beams for future colliders

Laser-driven Compton backscattering (CBS) has been proposed as method for controlling the intensity of colliding bunches in the FCC-ee so as to avoid the flip-flop instability caused by intensity asymmetry in colliding bunches. Laser-based collimation has also been proposed as an indestructible collimator for high-intensity electron beams. We have initiated a laboratory-based test program of these concepts with the E344 experiment at FACET-II. In this paper, we describe simulations of laser–beam interactions at FACET-II and the relevant scaling for FCC-ee. We also describe the experimental setup and diagnostics that will be used to make the measurements at FACET-II.

accelerator physics↗
DOE OSTI2026

Laboratory Tests of Laser Control of Electron Beams for Future Colliders

Laser-driven Compton backscattering (CBS) has been proposed as method for controlling the intensity of colliding bunches in the FCC-ee so as to avoid the flip-flop instability caused by intensity asymmetry in colliding bunches. Laser-based collimation has also been proposed as an indestructible collimator for high-intensity electron beams. We have initiated a laboratory-based test program of these concepts with the E344 experiment at FACET-II. In this paper, we describe simulations of laser-beam interactions at FACET-II and the relevant scaling for FCC-ee. We also describe the experimental setup and diagnostics that will be used to make the measurements at FACET-II.

Accelerator Physics (physics.acc-ph)↗
DOE OSTI2022

Stable electron beam propagation in a plasma column

The stability of plasma-based accelerators against transverse misalignments and asymmetries of the drive beam is crucial for their applicability. Without stabilizing mechanisms, even small initial offsets of the drive beam centroid can couple coherently to the plasma wake, grow, and ultimately lead to emittance degradation or beam loss for a trailing witness beam. In this work, we demonstrate the intrinsic stability of a beam propagating in a plasma column. This result is relevant in the context of plasma-based positron acceleration, where a wakefield suitable for the transport and acceleration of a positron witness beam is generated in a plasma column by means of an electron drive beam. The stable propagation of the drive beam is a necessary condition for the experimental implementation of this scheme. The differences and similarities of stabilizing mechanisms in a plasma column compared to a homogeneous plasma are identified via theory and particle-in-cell simulations. Experimental tolerances are given, demonstrating the experimental feasibility of the scheme.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1983

GaAs microwave devices and circuits with submicron electron-beam defined features

This paper describes the fabrication and application of GaAs FET's, both as discrete microwave devices and as the key active components in monolithic microwave integrated circuits. The performance of these devices and circuits is discussed for frequencies ranging from 3 to 25 GHz. The crucial fabrication step is the formation of the submicron gate by electron-beam lithography.

Wisseman, W. R.↗
DOE OSTI2021

Electron Beam Melting of Niobium Alloys from Blended Powders

Niobium-based tungsten alloys are desirable for high-temperature structural applications yet are restricted in practice by limited room-temperature ductility and fabricability. Powder bed fusion additive manufacturing is one technology that could be leveraged to process alloys with limited ductility, without the need for pre-alloying. A custom electron beam powder bed fusion machine was used to demonstrate the processability of blended Nb-1Zr, Nb-10W-1Zr-0.1C, and Nb-20W-1Zr-0.1C powders, with resulting solid optical densities of 99+%. Ultimately, post-processing heat treatments were required to increase tungsten diffusion in niobium, as well as to attain satisfactory mechanical properties.

36 MATERIALS SCIENCE↗
NASA NTRS1975

Experimental study of a free turbulent shear flow at Mach 19 with electron-beam and conventional probes

An experimental study of the initial development region of a hypersonic turbulent free mixing layer was made. Data were obtained at three stations downstream of a M = 19 nozzle over a Reynolds range of 1.3 million to 3.3 million per meter and at a total temperature of about 1670 K. In general, good agreement was obtained between electron-beam and conventional probe measurements of local mean flow parameters. Measurements of fluctuating density indicated that peak root-mean-square (rms) levels are higher in the turbulent free mixing layer than in boundary layers for Mach numbers less than 9. The intensity of rms density fluctuations in the free stream is similar in magnitude to pressure fluctuations in high Mach number flows. Spectrum analyses of the measured fluctuating density through the shear layer indicate significant fluctuation energy at the lower frequencies (0.2 to 5 kHZ) which correspond to large-scale disturbances in the high-velocity region of the shear layer.

Harvey, W. P.↗
NASA NTRS2006

Electron Beam Exposure of Thermal Control Paints on Carbon-Carbon and Carbon-Polyimide Composites

Carbon-carbon and carbon-polyimide composites are being considered for use as radiator face sheets or fins for space radiator applications. Several traditional white thermal control paints are being considered for the surface of the composite face sheets or fins. One threat to radiator performance is high energy electrons. The durability of the thermal control paints applied to the carbon-carbon and carbon-polyimide composites was evaluated after extended exposure to 4.5 MeV electrons. Electron exposure was conducted under argon utilizing a Mylar(TradeMark) bag enclosure. Solar absorptance and infrared emittance was evaluated before and after exposure to identify optical properties degradation. Adhesion of the paints to the carbon-carbon and carbon-polyimide composite substrates was also of interest. Adhesion was evaluated on pristine and electron beam exposed coupons using a variation of the ASTM D-3359 tape test. Results of the optical properties evaluation and the adhesion tape tests are summarized.

Jaworske, Donald A.↗