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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

On the significance of including the thermal motion of ions in determining the ion distribution behind a satellite

A comparative investigation concerning the spatial distribution of ions in the wake of small bodies was conducted using the theoretical wake models of Call (1969) and Parker (1976). Results for bodies with radius/ambient Debye length ratios of 2 and 5, with an electron temperature equal to the ambient electron temperature, and for the ionic Mach numbers S = 2, 4, 6, 8 are presented. Since the main physical difference between the models is in the consideration of the thermal motion of ions (Parker) versus ignoring this component (Call), a comparison between the models yields the quantitative significance of this component in determining the distribution of ions in the wake of artificial satellites. The application of this result to future experiments to be conducted on board the Spacelab and for any other large space platform in the area of space plasma physics is mentioned.

Samir, U.↗
DOE OSTI2023

Updates on the Wake Potential Calculations for the Electron-ion Collider with ECHO3D

ECHO3D has been used for calculating the geometric impedance and short-range wakefields for several EIC (Electron-Ion Collider) beamline vacuum components in the past few years. This note summarizes the wake potential calculations conducted in 2023 with ECHO3D for components from both the hadron storage ring (HSR) and the electron storage ring (ESR). For the HSR, calculations have been carried out for the polarimeter, the beam screen with pump slots and the bellow with pump ports. For the ESR, the short-range wake potential for the flange weld as well as various designs of the storage ring cavity have been calculated.

43 PARTICLE ACCELERATORS↗
NASA NTRS1997

Change in Ion Distribution Function While Crossing the Space Shuttle Wake

During the space shuttle/Spacelab 2 mission (STS-5]F) the Plasma Diagnostic Package (PDP) was placed in free flight in the vicinity of the Orbiter and provided the first opportunity to measure the midwake and far-wake regions of an orbiting spacecraft. During this period the PDP crossed the wake 4 times at downstream distances ranging from 40 m to 240 m. During each crossing a definite change in the ion-retarding potential curves was measured when the PDP was in the shuttle wake compared to the ambient ionosphere. These measurements were obtained by both the differential ion flux probe and the retarding potential analyzer instruments on the PDP. The temperature of the ions, derived from fitting the data to a Maxwellian distribution, are consistent with an enhancement during each wake crossing of as much as a factor of 2.5 (from about 0.08 eV to 0.2 eV). Such studies of plasma wakes were never before performed.

Sorensen, J. E.↗
DOE OSTI2023

Effect of emittance on performance of CeC scheme

In coherent electron cooling (CeC) the ions get cooled because their longitudinal positions with respect to a wake created by each ion in the electron bunch is correlated with an ion’s energy. A typical characteristic length of a CeC wake is just a few microns. Therefore, the coupling of a transverse and a longitudinal motion of both electrons and ions in a cooler must be taken into account. Below we estimate an additional path-length’s spread through the cooler, which particles have due to transverse emittance.

43 PARTICLE ACCELERATORS↗
NASA NTRS1985

Computer simulation of plasma electron collection by PIX-II

A wake model was defined for the NASCAP/LEO finite element model for the plasma interaction experiment (PIX-II) launched to study the interaction between high-voltage large solar arrays with the space plasma environment. The cell surface model considers the individual cells, distances between interconnects, and the fraction of surface covered by interconnects. Account is taken of the electrostatic potential around the spacecraft, which travels at 7500 mps, over five times the speed of thermal ions. Ram ions are produced ahead of the array and the wake ion density is described with a geometric shadowing model. The model correctly predicted the currents in high and low bias voltages when compared to orbital data. The panel snapover, however, was projected to occur at 100 V and instead occurred at 300 V, which indicates that the snapover state is bistable. Finally, a low potential was both predicted and measured in the wake.

Mandell, M. J.↗
NASA NTRS1992

Laboratory study of the temporal evolution of the current-voltage characteristic of a probe in the wake of an object immersed in a pulsed flowing plasma

Measurements of the current-voltage characteristics of a Langmuir probe in the near wake of a disk immersed in a pulsed flowing plasma were made. A 1 cm diameter biasable sphere was placed in the ion-free near wake region of a 10 cm diameter disk immersed in a Mach 8 pulsed flowing plasma. The current-voltage characteristic of the sphere was observed as a function of time as the sphere bias was scanned from -5000 V to +1000 V. The collected current is found to be monotonically increasing with increasing positive bias voltage but exhibits a threshold voltage for current collection as the bias voltage becomes more negative. Potential measurements in the wake region were made for a sphere bias voltages below, at, and above the current collection threshold for a number of times during the wake formation period. The time evolution of the potential profile is shown to change as the sheath around the biased sphere is established. Predictions from the particle trajectory code SIMION are compared with data, showing excellent agreement in the prediction of the current collection threshold.

Meassick, S.↗
DOE OSTI2022

Ion dynamics driven by a strongly nonlinear plasma wake

Abstract In plasma wakefield accelerators, the wave excited in the plasma eventually breaks and leaves behind slowly changing fields and currents that perturb the ion density background. We study this process numerically using the example of a Facility for Advanced aCcelerator Experimental Tests (FACET) experiment where the wave is excited by an electron bunch in the bubble regime in a radially bounded plasma. Four physical effects underlie the dynamics of ions: (1) attraction of ions toward the axis by the fields of the driver and the wave, resulting in formation of a density peak, (2) generation of ion-acoustic solitons following the decay of the density peak, (3) positive plasma charging after wave breaking, leading to acceleration of some ions in the radial direction, and (4) plasma pinching by the current generated during the wave-breaking. The interplay of these effects results in the formation of various radial density profiles, which are difficult to produce in any other way.

Physics↗
NASA NTRS1988

A study of single and binary ion plasma expansion into laboratory-generated plasma wakes

Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory.

Wright, Kenneth Herbert, Jr.↗
NASA NTRS1987

Effect of object potentials on the wake of a flowing plasma

The structure of the electric potential and ion density of the ion front in the near wake created by the flow of synthetic plasma past a conducting plate was investigated experimentally and numerically, with particular attention given to the effect of plate potential on the structure of the ion front. Results were obtained for a molecular nitrogen plasma with ambient electron densities of about 100,000/cu cm, ion temperatures of about 0.025 eV, electron temperatures of about 0.3 eV, and plasma flow velocities of about 10,000 m/s. Two-dimensional simulations of the laboratory experiments were performed by using a multiple waterbag technique. The calculated and experimental results show that wake closure is well described by the acceleration of ions in the plasma steady-state electric field. However, the ion-front motion is strongly affected by the imposed potential of the object creating the wake.

Katz, I.↗
NASA NTRS1979

The near-wake structure of the Atmosphere Explorer C /AE-C/ satellite - A parametric investigation

Measurements of ion current, electron temperature, and values of space potential obtained from the cylindrical electrostatic probe on board the Atmosphere Explorer C (AE-C) satellite were used to examine, in a parametric manner, the angular distribution of charge around the satellite. Interest is focused on nighttime equatorial data in the altitude range 275-620 km, which yields a wide range for the parameter R sub D (the radius of the satellite divided by the ambient value of the Debye lengths), including R sub D greater than 100, which is of practical significance to large space platforms. The variations of normalized ion current in the wake zone of the AE-C satellite appear to display an exponential dependence on R sub D for 'constant' values of other relevant parameters. The angular variations of electron temperature and space potential in the close vicinity of the satellite's surface were examined and compared with results from the Explorer 31 satellite. The variation of the ratio of measured to computed space potential with electron temperature was examined using data from both the AE-C and Explorer 31 satellites. It was found that the ratio is greater than unity. Possible causes for the above inequality are discussed.

Samir, U.↗
NASA NTRS1990

Ion mass spectrometer measurements from the Space Shuttle

Ion-mass-spectrometer measurements made, as part of the University of Iowa's Plasma Diagnostic Package, on the STS-3 and Spacelab 2 missions, sampled a variety of positive ion composition perturbations in response to gas emissions from the vehicle. A background of contaminant ion species (mostly relating to water) always exists in the vicinity of the Shuttle. The measured number fluxes of the contaminant ions vary differently from those of the ambient ions in response to changes in the spectrometer and spacecraft angles of attack. There is a near-Shuttle wake cavity in the contaminant ion distributions which has a different spatial configuration than the wake of the ambient ions. Although water dumps produce the longest term ion perturbations, the most well defined effects were observed from measurements taken during the short firings of the reaction-control-system thrusters.

Grebowsky, J. M.↗
NASA NTRS1989

Results of the first statistical study of Pioneer Venus Orbiter plasma observations in the distant Venus tail - Evidence for a hemispheric asymmetry in the pickup of ionospheric ions

Pioneer Venus Orbiter plasma and magnetometer observations from the first nine tail seasons of crossings of the Venus wake are used to study ion pickup in the far wake of an unmagnetized object embedded in the solar wind. This statistical study treats all of the plasma spectra containing pickup ions in the vicinity of the Venus tail. A hemispheric asymmetry is found in the pickup of ionospheric ions, with approximately four times more O(+) events observed in the 'northern' magnetic hemisphere (where the induced electric field points outward) than in the 'southern' magnetic hemisphere. Out of a total of 167 large O(+) events, 125, or 75 percent, occurred in the northern hemisphere when position is calculated in terms of Venus radii, and 129 or 77 percent occurred in the 'northern' hemisphere when position is expressed in gyroradii. This hemispheric asymmetry in ion pickup is consistent with the prediction of the Cloutier et al. (1974) mass loading model for Venusian ions above the ionopause boundary.

Intriligator, Devrie S.↗
DOE OSTI2020

Shocks propagate in a 2D dusty plasma with less attenuation than due to gas friction alone

In a dusty plasma, an impulsively generated shock, i.e., blast wave, was observed to decay less than would be expected due to gas friction alone. In the experiment, a single layer of microparticles was levitated in a radio frequency glow-discharge plasma. In this layer, the microparticles were self-organized as a 2D solid-like strongly coupled plasma, which was perturbed by the piston-like mechanical movement of a wire. To excite a blast wave, the wire's motion was abruptly stopped, so that the input of mechanical energy ceased at a known time. It was seen that, as it propagated across the layer, the blast wave's amplitude persisted with little decay. This result extends similar findings, in previous experiments with 3D microparticle clouds, to the case of 2D clouds. In our cloud, out-of-plane displacements were observed, lending support to the possibility that an instability, driven by wakes in the ion flow, provides energy that sustains the blast wave's amplitude despite the presence of gas damping.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1985

Three-dimensional calculation of shuttle charging in polar orbit

The charged particles environment in polar orbit can be of sufficient intensity to cause spacecraft charging. In order to gain a quantitative understanding of such effects, the Air Force is developing POLAR, a computer code which simulates in three dimensions the electrical interaction of large space vehicles with the polar ionospheric plasma. It models the physical processes of wake generation, ambient ion collection, precipitating auroral electron fluxes, and surface interactions, including secondary electron generation and backscattering, which lead to vehicle charging. These processes may be followed dynamically on a subsecond timescale so that the rapid passage through intense auroral arcs can be simulated. POLAR models the ambient plasma as isotropic Maxwellian electrons and ions (0+, H+), and allows for simultaneous precipitation of power-law, energetic Maxwellian, and accelerated Gaussian distributions of electrons. Magnetic field effects will be modeled in POLAR but are currently ignored.

Cooke, D. L.↗
NASA NTRS2000

Research on Orbital Plasma: Electrodynamics (ROPE)

Enhancements of the temperature of electrons in spacecraft plasma wakes have been reported for numerous cases and this phenomenon has been discussed both empirically and theoretically. However, very few measurements seem to have been made of the ion temperature within plasma wakes-possibly because the great majority of ion measurements were focussed on obtaining geophysical parameters and, hence, were confined to the region ahead of the spacecraft. Recently, however, an enhancement of the temperature of ions was discovered in data obtained in the wake of the Space Shuttle during the Spacelab-2 mission. At the time of that publication, this was the only known observation of this type. Herein, we report an additional case of ion temperature enhancement in a plasma wake. The data were taken during the Tethered Satellite System Reflight mission (TSS-1R) in the wake of the tethered satellite during passive (no current flow) operations. The measurements were obtained with the Differential Ion Flux Probe, or DIFP.

Samir, Uri↗
NASA NTRS1985

Interaction of Titan's atmosphere with Saturn's magnetosphere

The Voyager 1 measurements made during the Titan flyby reveal that Saturn's rotating magnetospheric plasma interacts directly with Titan's neutral atmosphere and ionosphere. This results from the lack of an intrinsic magnetic field at Titan. The interaction induces a magnetosphere which deflects the flowing plasma around Titan and forms a plasma wake downstream. Within the tail of the induced magnetosphere, ions of ionospheric origin flow away from Titan. Just outside Titan's magnetosphere, a substantial ion-exosphere forms from an extensive hydrogen-nitrogen exosphere. The exospheric ions are picked up and carried downstream into the wake by the plasma flowing around Titan. Mass loading produced by the addition of exospheric ions slows the wake plasma down considerably in the vicinity of the magnetopause.

Hartle, R. E.↗
NASA NTRS1974

Laboratory simulation of space aerodynamic phenomena - Satellite wake studies

The reasons for and the results of laboratory simulation studies of space plasma flow over obstacles are discussed in the context of satellite-ionosphere interactions and of forthcoming Skylab experiments. So far, it appears that ions passing through the plasma sheath are focused onto the wake axis, thereby creating an enhanced ion current which peaks at approximately a 'Mach' number of radii downstream from floating spherical bodies. The location of the peak enhancement shows a hyperbolic dependence on body potential, while its structure depends on the body cross-sectional geometry rather than on the axial dimension. There is a corresponding enhancement of the electron current coexistent with the ion-current enhancement. An electron temperature enhancement can sometimes occur in the near-wake 'ion void' region with a magnitude inversely proportional to charged particle density. Some supplementary experiments are suggested to support the planned Skylab experiments.

Samir, U.↗