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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Generation of broadband noise in the magnetotail

The generation of electrostatic noise in the geomagnetic tail by ion beams is evaluated, assuming a stationary plasma-sheet electron distribution and streaming-ion distributions. Both warm ion streams, as observed within the plasma-sheet boundary layer, and cold ion streams, as expected from upward flowing ionospheric ions, are considered. Warm ion streams by themselves are found to be stable, whereas a cold ion stream by itself is unstable to the beam acoustic mode. However, wave growth is increased if both cold and warm streams are simultaneously present. These results suggest that the interaction between the warm and cold ion streams is responsible for the peak in electrostatic-wave intensities observed within the plasma-sheet boundary layer. For cold and warm ions streaming in the same direction, wave-growth peaks are found for wave normal angles theta = 0 deg and wave frequencies about 0.1 times the electron plasma frequency. However, for antiparallel streaming cold and warm ions, wave growth peaks near theta = 90 deg and wave frequencies are an order of magnitude smaller.

Dusenbery, P. B.↗
DOE OSTI2020

Wilson Prize article: Transverse phase-space manipulations in electron accelerators

I am honored and grateful that my contributions to phase-space manipulations in general, and emittance compensation specifically, have been recognized by the Wilson Prize. The purpose of this article is to bring together what I believe to be the most important elements of the broad topic of transverse phase-space manipulations, focusing on the underlying beam physics which enable these types of schemes. We see that emittance compensation can be categorized as an example of the larger class of nonsymplectic manipulations. While the discussion is specifically focused on electron beams, much of the physics can also pertain to ion beams.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Studying Corrosion Using Miniaturized Particle Attached Working Electrodes and the Nafion Membrane

We developed a new approach to attach particles onto a conductive layer as a working electrode (WE) in a microfluidic electrochemical cell with three electrodes. Nafion, an efficient proton transfer molecule, is used to form a thin protection layer to secure particle electrodes. Spin coating is used to develop a thin and even layer of Nafion membrane. The effects of Nafion (5 wt% 20 wt%) and spinning rates were evaluated using multiple sets of replicates. The electrochemical performance of various devices was demonstrated. Additionally, the electrochemical performance of the devices is used to select and optimize fabrication conditions. The results show that a higher spinning rate and a lower Nafion concentration (5 wt%) induce a better performance, using cerium oxide (CeO2) particles as a testing model. The WE surfaces were characterized using atomic force microscopy (AFM), scanning electron microscopy-focused ion beam (SEM-FIB), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and X-ray photoelectron spectroscopy (XPS). The comparison between the pristine and corroded WE surfaces shows that Nafion is redistributed after potential is applied. Our results verify that Nafion membrane offers a reliable means to secure particles onto electrodes. Furthermore, the electrochemical performance is reliable and reproducible. Thus, this approach provides a new way to study more complex and challenging particles, such as uranium oxide, in the future.

42 ENGINEERING↗
NASA NTRS1972

A 30-cm diameter bombardment thruster with a variable magnetic baffle

Variable magnetic baffles were used to allow a change in baffle geometry to improve thruster performance and stability. Test results are presented. Thruster performance characteristics were analyzed to show how magnetic baffle field strength can improve performance at a fixed beam current, as well as increase the range of ion beam current for throttling.

Bechtel, R. T.↗
NASA NTRS1972

A 30-cm diameter bombardment thruster with a variable magnetic baffle.

Thruster performance and stability over a range of beam currents is a function of the hollow cathode propellant flow which depends in part on the baffle geometry. Variable magnetic baffles have been used to allow a change in baffle geometry to improve thruster performance and stability. Test results of a 30-cm thruster with magnetic baffle are presented. Thruster performance characteristics are analyzed to show how the magnetic baffle field strength can improve performance at a fixed beam current, as well as increase the range of ion beam current for throttling.

Bechtel, R. T.↗
NASA NTRS1974

Eight-cm mercury ion thruster system technology

The technology status of 8 cm diameter electron bombardment ion thrusters is presented. Much of the technology resulting from the 5 cm diameter thruster has been adapted and improved upon to increase the reliability, durability, and efficiency of the 8 cm thruster. Technology discussed includes: dependence of neutralizer tip erosion upon neutralizer flow rate; impregnated and rolled-foil insert cathode performance and life testing; neutralizer position studies; thruster ion beam profile measurements; high voltage pulse ignition; high utilization ion machined accelerator grids; deposition internal and external to the thruster; thruster vectoring systems; thruster cycling life testing and thruster system weights for typical mission applications.

Source record↗
NASA NTRS1974

8-cm mercury ion thruster system technology

The technology status of 8-cm diameter electron bombardment ion thrusters is presented. Much of the technology resulting from the 5-cm diameter thruster has been adapted and improved upon to increase the reliability, durability, and efficiency of the 8-cm thruster. Technology discussed includes: dependence of neutralizer tip erosion upon neutralizer flow rate; impregnated and rolled-foil insert cathode performance and life testing; neutralizer position studies; thruster ion beam profile measurements; high voltage pulse ignition; high utilization ion machined accelerator grids; deposition internal and external to the thruster; thruster vectoring systems; thruster cycling life testing and thruster system weights for typical mission applications.

Source record↗
NASA NTRS1974

Electron impact excitation of Hg/+/

A crossed charged beam technique was employed in the investigation reported. The ion beam was crossed at right angles by a magnetically confined electron beam. Cross sections were determined as a function of electron impact energy. Considerable structure in the excitation cross section appears immediately above the threshold. It is pointed out that a primary application of cross sections is related to the calculation of plasma rate coefficients.

Crandall, D. H.↗
NASA NTRS1976

Industrial ion source technology

A 30 cm electron bombardment ion source was designed and fabricated for micromachining and sputtering applications. This source has a multipole magnetic field that employs permanent magnets between permeable pole pieces. An average ion current density of 1 ma/sq cm with 500 eV argon ions was selected as a design operating condition. The ion beam at this operating condition was uniform and well collimated, with an average variation of plus or minus 5 percent over the center 20 cm of the beam at distances up to 30 cm from the ion source. A variety of sputtering applications were undertaken with a small 10 cm ion source to better understand the ion source requirements in these applications. The results of these experimental studies are also included.

Kaufman, H. R.↗
NASA NTRS1996

A Green's function method for high charge and energy ion transport

A heavy-ion transport code using Green's function methods is developed. The low-order perturbation terms exhibiting the greatest energy variation are used as dominant energy-dependent terms, and the higher order collision terms are evaluated using nonperturbative methods. The recently revised NUCFRG database is used to evaluate the solution for comparison with experimental data for 625A MeV 20Ne and 517A MeV 40Ar ion beams. Improved agreements with the attenuation characteristics for neon ions are found, and reasonable agreement is obtained for the transport of argon ions in water.

Energy Transfer↗
NASA NTRS1981

Numerical simulation of the generation of electrostatic turbulence in the magnetotail

A two-dimensional plasma model is used to investigate the development of electrostatic turbulence in a magnetized plasma from plasma instabilities. The simulation consists of following the motion of 100,000 ions in their self-consistent electrostatic field. The electrons are treated as a constant neutralizing background. The instabilities modeled are driven by a ring-type velocity distribution and by interpenetrating ion beams in a time-variable magnetic field. Instability growth times are of the order of an ion gyroperiod in the case of the ring distribution and of the order of an ion plasma period in the case of the beam simulation. Maximum potential differences generated are of the order of the ion kinetic energies. These simulations demonstrate the cascade of wave energy to long wavelengths, thus showing the E x B turbulence can be generated from plasma microinstabilities. After the free energy feeding, the instabilities are exhausted, and wave energy at wavelengths less than an ion gyrodiameter decays quickly to equilibrium levels, while longer wavelength modes persist for much longer times. In one model with a time dependent, but spatially uniform, magnetic field the electric field energy at long wavelengths appeared to increase as a result of the increase of the magnetic field.

Swift, D. W.↗
NASA NTRS1991

Advanced electric propulsion research - 1990

An experimental study of impingement current collection on the accelerator grid of an ion thruster is presented. The equipment, instruments, and procedures being used to conduct the study are discussed. The contribution to this current due to charge-exchange ions produced close to the grid is determined using a volume-integration procedure and measured ion beam current design, computed neutral atom density and measured beam plasma potential data. This current, which is expected to be almost equal to that measured directly, is found to be an order of magnitude less. The impingement current determined by integrating the current density of ambient ions in the beam plasma close to the grid is found to agree with the directly measured impingement current. Possible reasons for the disagreement between the directly measured and volume integrated impingement currents are discussed.

Monheiser, Jeffery M.↗
NASA NTRS1989

Alpha particles in field-aligned beams upstream of the bow shock - Simulations

The possibility that field-aligned ion beams (FABs) formed by direct reflection could contain alpha particles is studied using self-consistent hybrid simulations of an oblique collisionless, supercritical shock. It is found that alpha particles can backstream from a shock in which the angle between the shock normal and the upstream magnetic field is 45 degrees. The deficit of alpha particles in the FABs, expressed as a relative density ratio to H(+) normalized to the solar wind He(2+) to H(+) density ratio, varies between about 0.1 and less than 0.01 and depends on the upstream H(+) and He(2+) temperatures.

Burgess, D.↗
NASA NTRS1978

Industrial ion source technology

An analytical model was developed to describe the development of a coned surface texture with ion bombardment and simultaneous deposition of an impurity. A mathematical model of sputter deposition rate from a beveled target was developed in conjuction with the texturing models to provide an important input to that model. The establishment of a general procedure that will allow the treatment of manay different sputtering configurations is outlined. Calculation of cross sections for energetic binary collisions was extened to Ar, Kr.. and Xe with total cross sections for viscosity and diffusion calculated for the interaction energy range from leV to 1000eV. Physical sputtering and reactive ion etching experiments provided experimental data on the operating limits of a broad beam ion source using CF4 as a working gas to produce reactive species in a sputtering beam. Magnetic clustering effects are observed when Al is seeded with Fe and sputtered with Ar(?) ions. Silicon was textured at a micron scale by using a substrate temperature of 600 C.

Kaufman, H. R.↗
DOE OSTI2024

Efficient laser-driven proton acceleration from a petawatt contrast-enhanced second harmonic mixed-glass laser system

Efficient laser-driven plasma acceleration of ion beams requires precision control of the target–plasma profile, which is crucial to optimize the laser energy transfer. Along the laser propagation direction, this can be achieved by tailoring the temporal structure of the laser pulse. We show for the first time that frequency-doubling of a short pulse (hundreds-femtosecond range) petawatt-class mixed-glass laser system, which results in temporal intensity contrast enhancement, enables surface and volumetric laser–energy coupling, and the acceleration of proton beams from few-nanometer-thick foil targets. Experimentally, maximum ion energies and laser-to-proton energy conversion efficiencies were found to be both maximized at optimum laser and target conditions manifested when the normalized target density nearly equalizes the normalized laser vector potential, which is in agreement with theory and simulations. These signatures are recognized as a unique indication of the interaction between ultra-intense laser pulses with high temporal intensity contrast and ultra-thin nanometer-scale targets. Transverse modulations of accelerated proton beams in the form of bubble- and ring-like structures measured in the thinnest targets provide additional evidence of volumetric laser-driven particle acceleration regimes and transitional features in ultra-thin foil targets specific to laser–plasma interactions characterized by a high temporal intensity contrast. These results open avenues in the generation of high contrast laser pulses from short-pulse-femtosecond petawatt mixed-glass laser systems and demonstrate the feasibility of this technique for applications requiring high laser intensity contrast with high efficiency.

Physics↗
NASA NTRS1988

Survey of low-frequency electromagnetic waves stimulated by two coexisting newborn ion species

Parallel electromagnetic instabilities generated by coexisting newborn hydrogen and oxygen ions are studied for different orientations of the interplanetary magnetic field with respect to the solar wind velocity. The wave growth dependence on the densities and temperatures of the newborn species is investigated. The results indicate that in most domains of the Brillouin plane each ion beam can excite resonant instabilities without undue influence from the other newborn ion species. Although comparable resonant instabilities are more efficiently generated by the lighter newborn ions in ion-rich environments, the growth stimulated by the heavier species can withstand large beam density decreases.

Brinca, Armando L.↗
NASA NTRS1987

Fast ion mass spectrometry and charged particle spectrography investigations of transverse ion acceleration and beam-plasma interactions

Ion acceleration transverse to the magnetic field in the topside ionosphere was investigated. Transverse acceleration is believed to be responsible for the upward-moving conical ion distributions commonly observed along auroral field lines at altitudes from several hundred to several thousand kilometers. Of primary concern in this investigation is the extent of these conic events in space and time. Theoretical predictions indicate very rapid initial heating rates, depending on the ion species. These same theories predict that the events will occur within a narrow vertical region of only a few hundred kilometers. Thus an instrument with very high spatial and temporal resolution was required; further, since different heating rates were predicted for different ions, it was necessary to obtain composition as well as velocity space distributions. The fast ion mass spectrometer (FIMS) was designed to meet these criteria. This instrument and its operation is discussed.

Gibson, W. C.↗
NASA NTRS1981

Additional extensions to the NASCAP computer code, volume 3

The ION computer code is designed to calculate charge exchange ion densities, electric potentials, plasma temperatures, and current densities external to a neutralized ion engine in R-Z geometry. The present version assumes the beam ion current and density to be known and specified, and the neutralizing electrons to originate from a hot-wire ring surrounding the beam orifice. The plasma is treated as being resistive, with an electron relaxation time comparable to the plasma frequency. Together with the thermal and electrical boundary conditions described below and other straightforward engine parameters, these assumptions suffice to determine the required quantities. The ION code, written in ASCII FORTRAN for UNIVAC 1100 series computers, is designed to be run interactively, although it can also be run in batch mode. The input is free-format, and the output is mainly graphical, using the machine-independent graphics developed for the NASCAP code. The executive routine calls the code's major subroutines in user-specified order, and the code allows great latitude for restart and parameter change.

Mandell, M. J.↗