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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Twenty-First Century Research Needs in Electrostatic Processes Applied to Industry and Medicine

From the early century Nobel Prize winning (1923) experiments with charged oil droplets, resulting in the discovery of the elementary electronic charge by Robert Millikan, to the early 21st century Nobel Prize (2002) awarded to John Fenn for his invention of electrospray ionization mass spectroscopy and its applications to proteomics, electrostatic processes have been successfully applied to many areas of industry and medicine. Generation, transport, deposition, separation, analysis, and control of charged particles involved in the four states of matter: solid, liquid, gas, and plasma are of interest in many industrial and biomedical processes. In this paper, we briefly discuss some of the applications and research needs involving charged particles in industrial and medical applications including: (1) Generation and deposition of unipolarly charged dry powder without the presence of ions or excessive ozone, (2) Control of tribocharging process for consistent and reliable charging, (3) Thin film (less than 25 micrometers) powder coating and Powder coating on insulative surfaces, (4) Fluidization and dispersion of fine powders, (5) Mitigation of Mars dust, (6) Effect of particle charge on the lung deposition of inhaled medical aerosols, (7) Nanoparticle deposition, and (8) Plasma/Corona discharge processes. A brief discussion on the measurements of charged particles and suggestions for research needs are also included.

Mazumder, M. K.↗
NASA NTRS1992

On non-local transport processes in the solar atmosphere

We review two mechanisms which can lend a non-local character to energy transport in the solar atmosphere, heat flux propagating in the form of collisionless electrons, and non-equilibrium ionization of hydrogen driven by ambipolar diffusion. Application of these processes to modelling of the lower transition region and upper chromosphere is considered.

Macneice, P.↗
NASA NTRS1976

Calculations of the Electron Energy Distribution Function in a Uranium Plasma by Analytic and Monte Carlo Techniques

Electron energy distribution functions were calculated in a U235 plasma at 1 atmosphere for various plasma temperatures and neutron fluxes. The distributions are assumed to be a summation of a high energy tail and a Maxwellian distribution. The sources of energetic electrons considered are the fission-fragment induced ionization of uranium and the electron induced ionization of uranium. The calculation of the high energy tail is reduced to an electron slowing down calculation, from the most energetic source to the energy where the electron is assumed to be incorporated into the Maxwellian distribution. The pertinent collisional processes are electron-electron scattering and electron induced ionization and excitation of uranium. Two distinct methods were employed in the calculation of the distributions. One method is based upon the assumption of continuous slowing and yields a distribution inversely proportional to the stopping power. An iteration scheme is utilized to include the secondary electron avalanche. In the other method, a governing equation is derived without assuming continuous electron slowing. This equation is solved by a Monte Carlo technique.

Bathke, C. G.↗
NASA NTRS1984

Track damage and erosion of insulators by ion-induced electronic processes

Track damage and the associated ejection of atoms and molecules from insulators, which occur as a result of ion-induced electronic excitation, are of interest both in their own right and because of the mechanisms through which the energy in the excited electrons is transformed into atomic motion. In this paper an overview is given of the phenomena that are observed. We show that there is a remarkable similarity between the damage profile along the ion's track in the solid and the yield of ejected atoms at the energy that corresponds to each point on the track. It is also seen that the density of extended defects (or, correspondingly, the ejected particle yield) appears to have a 'universal' form that is weakly dependent on the type of material. In the model presented this is a consequence of the inner-shell ionization of light elements in the solid by the incident ion; the resulting Auger decay produces an intense ionization spike that locally triggers the track formation/erosion process. This model allows the estimation of erosion yields/damage profiles for different ions and materials.

Tombrello, T. A.↗
NASA NTRSDate not supplied

Operational Health Physics for Radiation Source Payloads

Spacecraft payloads processed at the Kennedy Space Center (KSC) frequently include ionizing and nonionizing radiation sources that require controls to protect the health of the workers involved in the ground operations. At KSC, a robust radiation protection program ensures that radiation hazards are identified, and appropriate controls are implemented using a radiation use authorization (RUA) process and Radiation Protection Committee review and approval. The Health Physics Office provides monitoring and oversight to ensure compliance. A brief overview of health physics activities in support of the Mars 2020 mission will be described to illustrate the overall management of radiation sources during payload ground processing.

Kurt R Geber↗
NASA NTRS1985

Coupling of newborn ions to the solar wind by electromagnetic instabilities and their interaction with the bow shock

The process by which the solar wind assimilates newly ionized atoms is important for understanding the presence of planetary or interstellar helium in the solar wind, the dynamics of the Active Magnetospheric Particle Tracer Explorers (AMPTE) lithium releases in front of the earth's bow shock, and the formation of cometary tails. In this paper is examined how newborn ions can be coupled to the solar wind in the direction parallel to the magnetic field by means of electromagnetic instabilities driven by the distribution of newborn ions. The linear properties of three instabilities are analyzed and compared with numerical solutions of the linear dispersion equation, while their nonlinear behavior is followed by means of computer simulation to obtain the characteristic time for the pickup process. With a primary emphasis on the AMPTE lithiuim releases, various degrees of realism are introduced into the calculations to model the upstream conditions and the intersection of the lithium with the bow shock. It is shown that a time-dependent shock model is needed to correctly reproduce the amount of lithium which is transmitted through the shock and that the resulting lithium ion distribution is still likely to be subject to the same type of instabilities in the magnetosheath. Applications of these results to comets, in particular the artificial comet expected to be generated by the AMPTE barium release in the magnetosheath, is also briefly discussed.

Winske, D.↗
NASA NTRS1979

The violent interstellar medium

Observational evidence for high-velocity and high-temperature interstellar gas is reviewed. The physical processes that characterize this gas are described, including the ionization and emissivity of coronal gas, the behavior and appearance of high-velocity shocks, and interfaces between coronal gas and cooler interstellar gas. Hydrodynamical models for the action of supernova explosions and stellar winds on the interstellar medium are examined, and recent attempts to synthesize all the processes considered into a global model for the interstellar medium are discussed.

Mccray, R.↗
NASA NTRS2002

Software for Processing Flight and Simulated Data of the ATIC Experiment

ATIC (Advanced Thin Ionization Calorimeter) is a balloon borne experiment designed to measure the cosmic ray composition for elements from hydrogen to iron and their energy spectra from approx.50 GeV to near 100 TeV. It consists of a Si-matrix detector to determine the charge of a CR particle, a scintillator hodoscope for tracking, carbon interaction targets and a fully active BGO calorimeter. ATIC had its first flight from McMurdo, Antarctica from 28/12/2000 to 13/01/2001. The ATIC flight collected approximately 25 million events. A C++-class library for building different programs for processing flight and simulated data of the ATIC balloon experiment is described. This library is compatible with the ROOT-system and includes classes and methods for solving a number of problems as the following: Reading data files in different formats (raw-data format, ROOT-format, ASCII-format, different formats for simulated data); Transferring all these formats to the only inner format of the library; Reconstruction of trajectories of primary particles with BGO calorimeter only. The Monte-Carlo simulations with GEANT code were used to obtain the basic tables for computing error corridors and chi(sup 2)-values for the trajectories. Obtaining error corridors for searching for signal of primary particle in the Si-matrix; Searching for hit of primary particle in the Si-matrix with using of error corridor and other criteria (chi(sup 2)-values, agreement between signals in Si-matrix and in the upper layer of scintillator and others); Determination of charge of primary particle; Determination of energy deposit in BGO calorimeter.

Panov, A. D.↗
NASA NTRS1973

Re-187, recycling r-process elements through stars, and the age of the Galaxy.

The enhanced beta-decay rate of ionized Re-187 in stars has been studied within the context of a detailed numerical model of the production of r-process elements and their recycling through stars during the course of galactic evolution. It is concluded that the enhanced decay rate does not significantly reduce the Re-Os chronometer age for the Galaxy. Consequently, the Re-187 beta-decay half-life and the Os-186/Os-187 neutron cross-section ratio remain as the significant uncertainties in this chronology. Unlike the uncertainties in other chronologies, both are amenable to laboratory measurements.

Talbot, R. J., Jr.↗
NASA NTRS1985

Ion loss processes in the stratosphere

Small ions consisting of aggregates of a few molecules determine th stratospheric electrical parameters such as conductivity, mobility, etc. The small ion density is controlled by the ionizing mechanisms for the production of ions and electrons and the loss processes for these charged particles. Ion production in stratosphere is chiefly due to galactic cosmic rays, and the loss processes due to recombination and attachment. Free electrons do not exist at stratospheric heights. The primary positive ion O2+ and the electrons are converted into complex clusters of positive and negative ions. The equilibrium ion density is governed by the equation of continuity for the production and loss of these ions. In the generalized equation of continuity, the gain or loss of ions due to transport is neglected. When aerosols or particulates are not present in the atmosphere, ions are loss due to ion-ion recombination. In the presence of aerosols, small ions can also be lost by attachment to the aerosols, and thus aerosols are likely to cause perturbations in the stratosphere electrification. A simplified model approach is adopted to study the effect of aerosols on the equilibrium ion density. The results of the analysis for the equatorial station Thumba (8.5 deg N) are presented.

Prasad, B. S. N.↗
NASA NTRS1981

Defect chemistry and characterization of Hg(1-x)Cd(x)Te

Undoped mercury cadmium telluride crystals were subjected to high temperature equilibration at temperatures ranging from 400 C to 655 C in various Hg atmospheres. Hall effect and mobility measurements were carried out on the crystals quenched to room temperature subsequent to the high temperature equilibration. The variation of the hole concentration in the cooled crystals at 77 K as a function of the partial pressure of Hg at the equlibration temperatures, together with a comparison of the hole mobility in the undoped samples with that in the copper and phosphorous doped samples yielded a defect model for the undoped crystals, according to which, the undoped crystals are essentially intrinsic at the equilibration temperatures and the native acceptor defects are doubly ionized. Native donor defects appear to be negligible in concentration, implying that the p to n conversion in these alloys is mainly due to residual foreign donor impurities. The thermodynamic constants for the intrinsic excitation process as well as for the incorporation of the doubly ionized native acceptor defects in the undoped crystals were obtained.

Vydyanath, H. R.↗
NASA NTRS1984

Turbulent compressible convection in a deep atmosphere. II - Two-dimensional results for main-sequence A5 and F0 type envelopes

In the present two-dimensional numerical study of turbulent compressible convection in the A5 and F0 main-sequence envelope types, ionization effects are included in the equation of state of the gas, and radiative transfer is modeled in a diffusive process with tabulated gas opacities. It is noted that the thermal effects of ionization significantly affect the dynamics of the flows and that an inversion of the mean density can be created and sustained in a dynamical situation. The substantial differences in the flows of A5 and F0 indicate development trends in the transition from the radiative to the convective mode of energy transport. As convection becomes more effective, the flow becomes more turbulent and the scaling effects of local scale heights become more significant.

Sofia, S.↗
NASA NTRS1974

The day side mid-latitude plasma trough

Above 2500 km the electrostatic probe experiment aboard the Isis 1 satellite detects a persistent dayside midlatitude plasma trough. The superposition of measurements taken over two-week intervals at noon is used to illustrate the form and location of the quiet time trough within each season. These measurement results contrast with those observations of a less prominent dayside trough at altitudes below 2500 km. Associated with the trough above 2500 km is an electron temperature maximum of about 6000 K that is sharp at midnight and broad at noon. In spring and summer a second noontime temperature maximum often appears poleward of 70-deg invariant latitude accompanied by an enhancement in the ionization. When it is assumed that the geophysical processes producing a plasmasphere act most directly upon the light ions, one factor contributing to the distinction between the plasma trough and the equatorial plasmapause is the increasing influence of O(+) on total plasma behavior at lower altitudes. Other factors are the local processes, such as dayside F region photoionization by energetic cusp particles that produce enhancements in plasma density and electron temperature.

Miller, N.↗
NASA NTRS1982

The cometary atmosphere and its interaction with the solar wind

The present state of knowledge of cometary atmospheres and their interaction with the solar winds is assessed. Current models of the magnetospheres and ionospheres of comets are based on either an atmospheric chemistry approach, minimizing the effects of atmospheric dynamics and thermodynamics, while the other method takes the exact opposite viewpoint and roles and significance are reversed. A major difficulty in completing the models is a lack of data on the chemical composition of the cometary nucleus, although UV observations have revealed the H, C, O, and S elemental abundance ratios. It is suggested that further studies of collisional ionization by energetic electrons be performed to characterize processes in the cometary atmosphere. Hydronium may be the dominat molecule in the inner coma, if the assumption that the ionosphere is a magnetic field-free cavity separated from the solar wind by an unyielding tangential discontinuity surface is accurate. Particular observations and theoretical attention are recommended for the solar wind interaction in the intermediate range, i.e., 2.5-5 AU, when the cometary atmosphere develops.

Mendis, D. A.↗
NASA NTRS1987

Experimental Resonance Enhanced Multiphoton Ionization (REMPI) studies of small molecules

Resonance enhanced multiphoton ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of exciting opportunities for both basic and applied science. On the applied side, REMPI has great potential as an ultrasensitive, highly selective detector for trace, reactive, or transient species. On the basic side, REMPI affords an unprecedented means of exploring excited state physics and chemistry at the quantum-state-specific level. An overview of current studies of excited molecular states is given to illustrate the principles and prospects of REMPI.

Dehmer, J. L.↗
NASA NTRS1991

Solar wind models

The understanding of the solar wind is based upon Parker's (1958) description of a thermally driven subsonic - supersonic outflow from a fully ionized electron-proton corona. The basic physical processes of thermally driven solar wind models are discussed. Also studied are the effect of alpha particles in the corona on the solar wind proton flux. The acceleration of the solar wind by Alfven waves is discussed.

Leer, Egil↗
NASA NTRS2001

Creation and utilization of a World Wide Web based space radiation effects code: SIREST

In order for humans and electronics to fully and safely operate in the space environment, codes like HZETRN (High Charge and Energy Transport) must be included in any designer's toolbox for design evaluation with respect to radiation damage. Currently, spacecraft designers do not have easy access to accurate radiation codes like HZETRN to evaluate their design for radiation effects on humans and electronics. Today, the World Wide Web is sophisticated enough to support the entire HZETRN code and all of the associated pre and post processing tools. This package is called SIREST (Space Ionizing Radiation Effects and Shielding Tools). There are many advantages to SIREST. The most important advantage is the instant update capability of the web. Another major advantage is the modularity that the web imposes on the code. Right now, the major disadvantage of SIREST will be its modularity inside the designer's system. This mostly comes from the fact that a consistent interface between the designer and the computer system to evaluate the design is incomplete. This, however, is to be solved in the Intelligent Synthesis Environment (ISE) program currently being funded by NASA.

NASA Discipline Radiation Health↗