| Initial Plasma Tests of the IPROSEC Cathode Device |
JUN 2007 |
13 pages |
| Authors:
A. T. Wheelock; D. L. Cooke; M. W. Geis; AIR FORCE RESEARCH LAB HANSCOM AFB MA
|
 | The Ion Proportional Surface Emission Cathode (IProSEC) is a low-brightness cathode technology under development for applications where large areas are available for emission and it is advantageous to avoid the space charge effects often associated with bright or intense sources. Space applications include spacecraft charge control and electrodynamic tethers. Surface Emission Cathodes emit electrons by concentrating an electric field between a p-doped insulating substrate and an adjacent metal cathode element. ... |
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| Ionospheric F-Region Storms: Unsolved Problems |
01 JUN 2006 |
21 pages |
| Authors:
Gerd W. Proelss; BONN UNIV (GERMANY F R)
|
| Befitting the venue of this meeting, we first investigate the polar ionosphere. The most pressing problem here is that no reliable description of this region is available, not even for undisturbed conditions. To improve on this situation we have investigated the properties of some of the more prominent anomalies observed in this region, including the heating effect below the magnetospheric cusp, the subauroral electron temperature enhancement and the main ionospheric ... |
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| Magnetically Filtered Faraday Probe for Measuring the Ion Current Density Profile of a Hall Thruster |
JAN 2006 |
9 pages |
| Authors:
Joshua L. Rovey; Mitchell L. R. Walker; Alec D. Gallimore; Peter Y. Peterson; MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
|
| The ability of a magnetically filtered Faraday probe (MFFP) to obtain the ion current density profile of a Hall thruster is investigated. The MFFP is designed to eliminate the collection of low-energy, charge-exchange (CEX) ions by using a variable magnetic field as an ion filter. In this study, a MFFP, Faraday probe with a reduced acceptance angle (BFP), and nude Faraday probe are used to measure the ion current density ... |
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| A Novel Polymer-Synthesized Ceramic Composite Based System for Bone Repair: Osteoblast Growth on Scaffolds with Varied Calcium Phosphate Content |
13 JUL 2005 |
5 pages |
| Authors:
Yusuf M. Khan; Dhirendra S. Katti; Cato T. Laurencin; DREXEL UNIV PHILADELPHIA PA
|
| Polymer/ceramic composite matrices for bone tissue engineering were constructed by synthesizing a poorly crystalline calcium phosphate within poly(lactide-co-glycolide) microspheres that were subsequently fused together to form 3-dimensional structures. Calcium ion dissolution from the composite matrices in simulated body fluid was examined over a 24 hour period. The initial 4 hour period showed an increase in calcium ion concentration, whereas, a decrease in calcium ion concentration was noted thereafter. This decrease ... |
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| Plume Expansion and Ionization in a Micro Laser Plasma Thruster |
JUN 2005 |
14 pages |
| Authors:
Michael P. Reilly; George H. Miley; William A. Hargus Jr; ILLINOIS UNIV AT URBANA
|
| Ion density measurements have been performed on the plasma generated by an ablative diode laser thruster using a negatively biased flat plate probe. The biased probe data was coupled with measurement of the ablation crater through use of a scanning electron microscope (SEM). The SEM was used to analyze the post-pulse ablation spots to determine the volume of fuel ablated. The micro-laser plasma thruster (micro-LPT) discussed here ablates a target ... |
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| Numerical Modeling of the Hall Thruster Discharge |
01 APR 2005 |
119 pages |
| Authors:
Felix I. Parra; Eduardo Ahedo; Manuel Martinez-Sanchez; John Michael Fife; D. Escobar; Juan Rus; V. Lapuerta; A. Molina; UNIVERSIDAD POLITECNICA DE MADRID (SPAIN) ETSI AERONAUTICOS
|
| This collection of seven previously published papers performed under Grant No. FA8655-04-1-3003 provide the background for the development of a new version of the HPHall hybrid code (HPHallv.2) for the numerical modeling of Hall Thruster discharge and new insights on discharge physics obtained during the development. |
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| Etching Characteristics and Surface Analysis of Molecular Bean Epitaxy Grown P-Type Aluminum Gallium Nitride With Boron Trichloride/Chlorine Gases in Inductively Coupled Plasma (ICP) Dry Etching |
NOV 2004 |
21 pages |
| Authors:
Fred Semendy; Phillip Boyd; Unchul Lee; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
|
| Dry etching of magnesium doped p-type aluminum gallium nitride grown by molecular beam epitaxy (MBE) has been carried for the first time by inductively coupled plasma (ICP) system via the boron trichloride/chlorine (BCl3/Cl2) gas system with variations in chuck power, ICP power, chlorine (Cl2) ratio in Cl2/BCl3 and process pressure. Processed samples were cleaned by standard techniques, depths were measured, and etching rates and selectivity were calculated. Surface morphology of ... |
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| Evaluation of a Magnetically-Filtered Faraday Probe for Measuring the ion Current Density Profile of a Hall Thruster |
JUL 2004 |
15 pages |
| Authors:
Joshua L. Rovey; Micthell L. Walker; Alec D. Gallimore; Peter Y. Peterson; MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
|
| The ability of a magnetically-filtered Faraday probe (MFFP) to obtain the ion current density profile of a Hall thruster is investigated. The MFFP is designed to eliminate the collection of low energy, charge-exchange (CEX) ions by using a variable magnetic field as an ion filter. In this study, a MFFP, boxed Faraday probe (BFP), and nude Faraday probe are used to measure the ion current density profile of a 5 ... |
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| Numerical Computation in MagnetoFluid Dynamics |
30 JUN 2004 |
30 pages |
| Authors:
R. W. MacCormack; STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| During the years supported by the subject AFOSR grant the following research accomplishments were made. Inclusion of both thermal and chemical non- equilibrium into the MFD equations. Simulation of the flow within MFD generators and accelerators for the proposed energy "bypass scram jet engine" concept. Reformulating the governing MFD equations for strong imposed magnetic fields, of the order of 10 Tesla, using the properties of the imposed magnetic fields, V. ... |
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| Recombining Plasma Expanding in Low-Pressure Region |
07 APR 2004 |
1 pages |
| Authors:
R. P. Dahiya; INDIAN INST OF TECH NEW DELHI
|
| High density thermal plasma expanding in low-pressure region is of immense scientific interest and has numerous applications. The monomer seeded plasma is utilized for plasma processing of surfaces, i.e. deposition, surface etching, nitriding and for many more applications depending on the seeding materials. Conditions prevailing in the Tokomak edge plasma can also be simulated using the low temperature, high flux obtained with cascaded arc thermal plasma source. Various species of ... |
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| Synthesis of Aerogel-Metal Cluster Composites by Gamma Radiolysis |
2003 |
6 pages |
| Authors:
Massimo F. Bertino; Jared F. Hund; Guohui Zhang; Chariklia Sotiriou-Leventis; Nicholas Leventis; MISSOURI UNIV-ROLLA
|
| Noble metal clusters (Ag, Au) were formed in a silica aerogel matrix by gamma irradiation of hydrogel precursors loaded with aqueous solutions containing Ag+ or AuCl4 ions. Hydrogels exposed to gamma rays assumed the color expected for colloidal suspensions of Ag (respectively Au) clusters. The hydrogels were subsequently washed and supercritically dried, without any evident change in color, indicating that the metal clusters were not removed during drying. Typical gamma ... |
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| 3-D Computation of Surface Sputtering and Redeposition Due to Hall Thruster Plumes |
23 DEC 2002 |
11 pages |
| Authors:
J. M. Fife; M. R. Gibbons; W. A. Hargus; D. B. VanGilder; D. E. Kirtley; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| A 3-D computational plasma interaction modeling system is being developed to predict the interaction of electric propulsion plumes with surfaces. The system, named COLISEUM, Is designed to be flexible, usable, and expandable, allowing users to define surfaces with their choice of off-the-shelf 3-D solid modeling packages. These surfaces are then loaded into COLISEUM, which calculates plasma expansion from electric thrusters using a variety of functional modules. Functional modules are interchangeable, ... |
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| Thrust, Ion Current Density and Energy Distribution Measurements of the BPT-4000 Hall Effect Thruster |
JUL 2002 |
3 pages |
| Authors:
James Haas; Scott Engleman; Ronald Spores; Kristi DE Grys; David King; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE WEST
|
| On-going General Dynamics (GD) and Air Force Research Laboratory (AFRL) research is presented, attempting to better understand the causes of the observed Beginning of Life (BOL) performance degradation of the BPT-4000 Hall thruster. Although current thruster performance meets the minimal mission requirements for average performance, reduction or elimination of the performance decrease could yield a mission average performance increase of up to 6%. Extensive thrust stand measurements will be made ... |
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| The Development of a Flexible, Usable Plasma Interaction Modeling System |
13 JUN 2002 |
10 pages |
| Authors:
J. M. Fife; M. R. Gibbons; D. B. VanGilder; D. E. Kirtley; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| A 3-D computational plasma interaction modeling system is being developed to predict the interaction of electric propulsion plumes with surfaces. The system, named COLISEUM, is designed to be flexible, usable, and expandable, allowing users to define surfaces with their choice of off-the-shelf 3-D solid modeling packages. These surfaces are then loaded into COLISEUM which performs plasma operations based on user commands. Functional modules are interchangeable, and can range from simple ... |
|
| A Comprehensive Investigation of the Role of Vacuum Facility Pressure on High-Power Hall Thruster Testing |
JUN 2002 |
61 pages |
| Authors:
Alec D. Gallimore; Mitchell R. Walker; Richard R. Hofer; MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
|
| Closed-Drift Hall thrusters (CDTs) have great potential in satisfying many of the spacecraft propulsion needs of the United States Air Force for the next several decades. Its combination of high specific impulse, high thrust efficiency, and high thrust density makes it very attractive for a number of earth-orbit missions. However, due to the wide range of facilities used in CDT testing, it is difficult for researchers to make adequate comparisons ... |
|
| Ion Density Fluctuations in Plasma and Their Effects on Hot Electron Generation |
JUN 2002 |
61 pages |
| Authors:
Marty Wallace; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| In this thesis, high-energy electron generation by stimulated Raman scattering of intense laser light is investigated in computer simulations. These high-energy electrons can be used to produce a high-energy x-ray source for Nuclear Weapons Effects Testing. The simulation results are compared with actual experiments conducted at the Atomic Weapons Establishment in the United Kingdom. The simulations show that the heated electron temperature is significantly lowered and the frequency spectrum of ... |
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| Architecture and Initial Results of a 3-D Plasma Simulation System for Spacecraft-Thruster Interaction Assessment |
13 MAR 2002 |
10 pages |
| Authors:
J. M. Fife; M. R. Gibbons; D. B. VanGilder; D. E. Kirtley; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| A 3-D Plasma Interaction Modeling System (PIMS) is being developed to predict the interaction of electric propulsion plumes with surfaces. The system is designed to be flexible, usable, and expandable, allowing users to define and mesh surfaces with their choice of off-the-shelf 3-D solid modeling packages. These surfaces are then loaded into PIMS, which performs plasma operations based on user commands. Functional PIMS modules will range from simple (prescribed plume ... |
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| Space Systems Environmental Interaction Studies |
30 AUG 2001 |
|
| Authors:
M. A. Morgan; Alan C. Huber; David J. Sperry; Alan N. Donkin Jr.; Scott J. Moran; AMPTEK INC BEDFORD MA
|
 | This report describes the objectives and summarizes the outcome, of the work performed under this contract. In addition, and this constitutes the major portion of the report, a comprehensive summary of all the important design elements for the anticipated DIDM-3 instrument is presented herein. As the final effort of the contract, all of the various facets to designing and building a Digital Ion Drift Meter for inclusion in the Communication/Navigation ... |
|
| Quantum Devices and Nanostructures; QDN-2 |
27 JUL 2001 |
|
| Authors:
ETTORE MAJORANA CENTRE FOR SCIENTIFIC CULTURE ERICE (ITALY)
|
| This report consists of the schedule for the Second International School on Quantum Devices and Nanostructures, and contact information for the presenters, as well as selected abstracts of presentations. |
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| Differential Diffusion in Bistable Conditions |
19 JAN 2001 |
4 pages |
| Authors:
Greg Holloway; Ann Gargett; Bill Merryfield; INSTITUTE OF OCEAN SCIENCES SIDNEY (BRITISH COLUMBIA)
|
| Double diffusive phenomena, due to the difference in molecular conduction coefficients for heat and for ion concentrations in sea water, are widely known. These include salt fingering and diffusive convection which occur when either temperature or salinity is destabilizing while the other (salinity or heat) is stabilizing. Less well known, less dramatic in their occurrence, but far more widespread are circumstances where both temperature and salinity are stabilizing and yet ... |
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| Experimental Investigations with a 5-kW-Class Laboratory Model Closed- Drifted Hall Thruster |
JAN 2001 |
272 pages |
| Authors:
Alec D. Gallimore; Brian E. Gilchrist; R. P. Drake; Frank S. Gulczinski; James M. Haas; MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
|
| This final technical report summarizes research conducted at the Plasmadynamics and Electric Propulsion Laboratory (PEPL) to characterize the internal and plume plasma of a closed-drift Hall thruster (CDT). The project was composed of the following segments: 1) a 5-kW-class CDT (P5) was built and characterized in terms of performance and plume divergence; 2) the molecular- beam mass spectrometer (MBMS) was used to measure the ion energy distribution finction and charge ... |
|
| Method to Track Corrosion Environment in Aircraft |
JAN 2001 |
41 pages |
| Authors:
Sunil Menon; Steve Lewis; Ron Jiracek; HONEYWELL INC MINNEAPOLIS MN HONEYWELLLABORATORIES
|
| A Corrosion Environment Monitoring (CEM) system was developed as a data acquisition device designed to collect and store environmental data for military and commercial aircraft. Accurate and robust commercial off-the-shelf (COTS) sensor systems are combined with state-of-the-art processing units to capture and store a wide range of physical data related to the corrosion phenomena. The collected sensor data include temperature, humidity, pH concentration, chloride ion concentration, and the free potential ... |
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| Molecular Simulations of Concentrated Aqueous Solutions: Ionic Equilibrium Structures in Solutions |
2001 |
11 pages |
| Authors:
Witold M. Bartczak; Michael Zapolowski; Krystyna Wolf; LODZ TECHNICAL UNIV (POLAND)
|
| The computer simulation methods have been applied to study the structure of aqueous solutions of simple ionic salts in the region of very high concentrations. The calculations of ionic structures in solutions were performed for NaOH, NaCl, LiCl and MgCl2 solutions. The concentrations ranged from 0.2 M to saturated solutions, in some cases as much as 19 M. A particularly careful analysis was devoted to the topology of the ionic ... |
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| Dynamics of Diffusion-Controlled Recombination of Ions in Ionic Solutions. Limits of Validity of the Debye - Smoluchowski Equation |
2001 |
12 pages |
| Authors:
Krystyna Wolf; Witold M. Bartczak; LODZ TECHNICAL UNIV (POLAND)
|
| The diffusion and recombination process in an ensemble of isolated single pairs of opposite charges is usually described by the Debye Smoluchowski equation. The present work is an overview of a series of computer simulations of diffusion and recombination of ions in solution performed with the aim to determine the limits of validity of the Debye - Smoluchowski equation In the first part of the project, the calculations were performed ... |
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| Dawn/Dusk Dropouts Due to Storms/Substorms Near the Outer Radiation Belt: Observations From CRRESS |
20 SEP 2000 |
11 pages |
| Authors:
C. G. Mouikis; A. Korth; R. W. Friedel; J. Fennel; AEROSPACE CORP EL SEGUNDO CA LAB OPERATIONS
|
| We investigate particle dropout events from the dawn flank of the magnetosphere as observed from a variety of instruments on board the CRRES satellite. All dropouts are observed at magnetic latitudes more than 100 above the magnetic equator. Plasma and energetic electron and ion data help us establish the boundary regimes being sampled. During these events, the magnetic field shows a dramatic change in the ... |
|
| Advanced Radiation Theory Support, Annual Report 1999 |
22 MAY 2000 |
142 pages |
| Authors:
NAVAL RESEARCH LAB WASHINGTON DC RADIATION HYDRODYNAMICS BRANCH
|
| This program describes the work of the Radiation Hydrodynamics Branch during FY 99 in support of the DTRA PRS program. Critical issues covered are: (1) Theory and modeling of enhanced energy dissipation in Z-pinch plasmas, (2) Experimentally and theoretically comparing uniform fill versus annular shell gas puff behavior of a series of Ar:Ne mixture experiments on Saturn, (3) Large initial radius Z-pinch load behavior on Saturn, Double ... |
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| Interface Formation and Solid-Solid Reactions Induced by Cluster Ion Deposition |
16 DEC 1999 |
14 pages |
| Authors:
Scott L. Anders; UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY
|
| Development is reported of a unique phase-space-compressing ion deposition beamline, coupled to an ultrahigh vacuum surface preparation/analysis system. The performance of the beamline in low energy focused deposition is discussed. A system of transferrable, high precision sample holders is described. An embedded-atom code developed for simulation of the cluster impact behavior is described. Initial results are presented for deposition, sticking, and penetration of copper atoms ... |
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| Dawn/Dusk Dropouts due to Storms/Sub storms Near the Outer Radiation Belt: Observations from CRRES |
30 SEP 1999 |
9 pages |
| Authors:
C. G. Mouikis; A. Korth; R. H. Friedel; J. F. Fennell; AEROSPACE CORP EL SEGUNDO CA ENGINEERING AND TECHNOLOGY GROUP
|
| We investigate the particle dropout events from the dawn flank of the magnetosphere as observed from a variety of instruments on board the CRRES satellite. All dropouts are observed at magnetic latitudes more than 100 above the magnetic equator. Plasma and energetic electron and ion data help us establish the boundary regimes being sampled. During these events, the magnetic field shows a dramatic change in the ... |
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| Development of Computational Techniques for Studying Interpenetrating Plasma Flows and Microwave Impulse |
30 SEP 1999 |
37 pages |
| Authors:
Evgeniy L. Stupitsky; RUSSIAN ACADEMY OF SCIENCES MOSCOW HIGH ENERGY DENSITY RESEARCH CENTER
|
| This report results from a contract tasking High Energy Density Research Center (HEDRC) as follows: The contractor will simulate the merging plasma ensemble as three fluids one for the ion component of each plasma and one for a single common electron fluid. Issues which must be successfully addressed include conservation of momentum and energy, accommodating widely varying time scales for different processes, and avoidance of numerical ... |
|
| Advances in High Power Optical Fiber Lasers. Phase 1 |
14 SEP 1999 |
9 pages |
| Authors:
Wylangowski; HOPE TECHNOLOGIES INC LITTLE COMPTON RI
|
| We have proposed and carried out a series of experiments that could be of significance to the development of high power cladding pumped optical fiber lasers. First, at low power, we have shown how a more complex cavity can result in increased power by combining fiber lasers using a truncated 2x2 coupler. We believe that this can lead to the concatenation of many couplers while ... |
|
| Space Systems Environmental Interaction Studies |
30 AUG 1999 |
37 pages |
| Authors:
M. A. Morgan; Alan C. Huber; David J. Sperry; Alan N. Donkin Jr.; Scott J. Moran; AMPTEK INC BEDFORD MA
|
| Final system testing, performance characterization and documentation of the Digital Ion Drift Meter (DIDM-2) instrument were carried out in the period immediately prior to delivery, which transpired under Task #1 of this contract. Some details of these activities are provided. Also, a summary of the activities performed under Task #2, with regard to the SPREE and OEDIPUS-C data sets, is also presented. The work was terminated in this report period. ... |
|
| The Air Force Statistical Auroral Models (AFSAM): Functional Representations |
28 JUN 1999 |
85 pages |
| Authors:
William J. McNeil; RADEX INC BEDFORD MA
|
| We document here the Air Force Statistical Auroral Models (AFSAM), a set of empirical models for average auroral quantities. The quantities include electron and ion integral energy flux, number flux and average energy and the Pedersen and Hall conductivities. These quantities were computed by first computing average electron and ion spectra measured from the DMSP satellites, then converting these average spectra into the several quantities as a function of corrected ... |
|
| Simulation of Low Frequency Noise in a CCTWT |
27 MAY 1999 |
60 pages |
| Authors:
Charles K. Birdsall; J. P. Varboncoeur; P. J. Christensen; CALIFORNIA UNIV BERKELEY ELECTRONICS RESEARCH LAB
|
| The report describes the progress made studying the low frequency noise in a coupled cavity traveling wave tube. Simulations using the particle in cell code, XOOPIC, indicate that plasma is generated by the ionization of a background gas. The plasma is trapped in the potential depression of the beam, which is formed in the radial direction of the beam, which is formed in the radial direction by the radial space ... |
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| Biomolecular Mask Formation Using UV Patterened Sam Films |
30 APR 1999 |
5 pages |
| Authors:
Kenneth Douglas; COLORADO UNIV AT BOULDER DEPT OF PHYSICS
|
| The research focus has been on the challenging issues involved in achieving, two-dimensional recrystallization of protein (S-layer) monomers in large (-several hundred micron) single crystal areas. To acquire facility with the recrystallization process we first explored the experimental conditions which influence protein crystallization e.g., protein concentration. temperature, pH, ionic strength concentration of various mono- and divalent cations, etc. We attempted crystallization experiments in aqueous ... |
|
| Parameter Space for Collisionless RF Sheaths |
08 APR 1999 |
18 pages |
| Authors:
Wallace M. Manheimer; NAVAL RESEARCH LAB WASHINGTON DC FUNDAMENTAL PLASMA PROCESSES
|
| As plasma processing reactors approach higher ion density, the sheath models which neglect the rf response of the ions become invalid. This work shows that at arbitrary ion density, the nature of the collisionless rf ion sheath can be described in a number of different regimes of parameter space. These regimes can all be visualized on a single two dimensional plot where the horizontal axis is the ion plasma frequency ... |
|
| Studies of Ionospheric Plasma Electrodynamics |
JAN 1999 |
5 pages |
| Authors:
R. A. Heelis; TEXAS UNIV AT DALLAS RICHARDSON CENTERFOR SPACE SCIENCES
|
| During the course of this contract we researched a wide variety of topics principally concerning the transport of ionospheric plasma and the role of that transport in the generation and evolution of plasma irregularities. Support from this contract has yielded a wealth of information related to the behavior of the ionosphere and its characteristics that are relevant to total electron content and the appearance of plasma structures. |
|
| The Plasma Mantle: Polar Satellite Observations |
20 DEC 1998 |
12 pages |
| Authors:
J. F. Fennell; J. L. Roeder; M. Grande; C. Perry; R. Friedel; AEROSPACE CORP EL SEGUNDO CA TECHNOLOGY OPERATIONS
|
| Since launch in February 1996, the Polar satellite has made numerous traversals of the high-latitude dayside magnetosphere. These traversals have covered the high-altitude regions of the low-latitude boundary layer, cusp, cleft, mantle, and polar cap. Often, as the Polar satellite traverses the high- latitude dayside magnetosphere, it leaves the soft precipitation region of the cusp or cleft and enters into the mantle plasma. There, the angular distribution of 1 to ... |
|
| Histograms of Arecibo World Days Measurements and Linear-H Fits Between 1985 and 1995 |
30 NOV 1998 |
67 pages |
| Authors:
D. J. Melendez-Alvira; J. M. Picone; O. A. Kelley; Q. Zhou; M. P. Sulzer; NAVAL RESEARCH LAB WASHINGTON DC E O HULBURT CENTER FOR SPACE RESEARCH
|
| This document presents histograms of linear-H model fits to electron density profiles measured with the incoherent scatter radar of the Arecibo Observatory in Puerto Rico during the World Days between 1985 and 1995. The linear-H model is a four-parameter analytical function, which is shown to fit the measured electron density profiles with better than 10% accuracy. The histograms show the distribution of the four model parameters as well as statistical ... |
|
| Wall Effects Observed in Tissue-Equivalent Proportional Counters |
13 FEB 98 |
197 pages |
| Authors:
Steven E. Rademacher; COLORADO STATE UNIV FORT COLLINS DEPT OF RADIOLOGICAL HEALTH SCIENCES
|
| Tissue equivalent proportional counters (TEPC) have been used to measure energy deposition in simulated volumes of tissue ranging in diameter from 0.1 to 10 microns. There has been some concern that the wall used to define the volume of interest could influence energy deposition within the sensitive volume. These 'wall effects' occur because the wall has a density significantly greater than the cavity gas. Energy deposition measurements were made for ... |
|
| Measurement of the Diffusion Coefficient of Strongly Interacting Colloidal Suspensions by Nondegenerate Two-Wave Mixing |
1998 |
33 pages |
| Authors:
C. L. Adler; N. M. Lawandy; BROWN UNIV PROVIDENCE RI
|
| We have measured the diffusion coefficient of strongly interacting "colloidal liquids" near the "liquid"-"solid" phase transition using nondegenerate two-wave mixing. We self-consistently calculate the diffusion coefficient as the product of the elastic modulus and a relaxation time which is identified as the time taken for a particle to diffuse one-tenth of the average interparticle distance. This procedure also predicts an electrolyte concentration where the diffusion coefficient vanishes which is identified ... |
|
| The Source of the Low Latitude Boundary Layer |
98 |
3 pages |
| Authors:
Raymond J. Walker; Robert L. Richard; CALIFORNIA UNIV LOS ANGELES INST OF GEOPHYSICS AND PLANETARY PHYSICS
|
| Ion entry into the magnetosphere was studied for different interplanetary magnetic field (IMF) orientations. Field models for the study of ion entry were from the results of global magnetohydrodynamic (MHD) simulations. Ions entering under northward IMF conditions entered on reconnected field lines and entered the flanks of the magnetotail. Some were strongly accelerated during entry at high latitudes. Under southward IMF conditions particles entered through the plasma mantle and only ... |
|
| Expanded Capabilities for the Ionospheric Forecast Model |
20 DEC 97 |
149 pages |
| Authors:
R. W. Schunk; J. J. Sojka; J. V. Eccles; SPACE ENVIRONMENT CORP LOGAN UT
|
| The Ionospheric Forecast Model (IFM) is a computationally efficient, user friendly, model of the global ionosphere that was developed for operational use at the Space Forecast Center. The model provides 12 hours forecasts for the global distributions of the molecular (NO+, O2+, N2+) and O+ densities, and the electron and ion temperatures, at E and F region altitudes (90-1000 km). The model also contains a simple ... |
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| Quasineutral Particle Simulation of Magnetized Plasma Discharges: General Formalism and Application to ECR Discharges |
31 JUL 1997 |
52 pages |
| Authors:
Martin Lampe; Glenn Joyce; Wallace M. Manheimer; Steven P. Slinker; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
|
| In quasineutral plasmas it is difficult and inefficient to calculate the electrostatic field from Poisson's equation. We have developed a particle- in-cell/Monte Carlo (PIC/MC) simulation method for magnetized discharges, in which internal electric fields and sheath potentials are determined directly from the requirement of quasineutrality. Sheaths are treated as thin potential barriers, and the Bohm criterion for ion flux into the sheath is imposed as a boundary condition. Electron plasma ... |
|
| Computational Modeling of Expanding Plasma Plumes in Space Using a PIC- DSMC Algorithm |
19 JUN 97 |
313 pages |
| Authors:
Daniel E. Hastings; David Oh; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS
|
| A comprehensive computational model of the plume of a Hall Thruster is presented. Spacecraft-plume interaction issues are addressed by studying how a partially ionized plasma expands in three dimensions and interacts with the surfaces it encounters. A quantitative analysis of fundamental parameters is used to show that the plume is an unmagnetized, quasi-neutral plasma in which Charge Exchange collisions play a significant role. The electrons are shown to be isothermal ... |
|
| Atmospheric Ultraviolet Radiance Integrated Code (AURIC): Airglow Portion Providing Dayglow and Nightglow Spectral Radiances from 100 to 900 nm |
27 JAN 97 |
92 pages |
| Authors:
D. J. Strickland; T. Majeed; J. S. Evans; P. M. Shen; J. E. Bishop; COMPUTATIONAL PHYSICS INC FAIRFAX VA
|
| The work reported let to a suite of codes for characterizing dayglow and nightglow and for ingesting Rayleigh scattered radiances (solar and lunar) from MODTRAN. The key outputs are spectral radiances at satellite altitudes for any viewing angle. The wavelength range is from approximately 100 to approximately 900 nm and, for dayglow, contains all prominent band systems and lines, including HI 121.6 nm and OI 130.4 nm. Chemistry models are ... |
|
| Apparatus for Measuring Lead Content of Water. |
21 JAN 1997 |
|
| Authors:
Cesar Clavell Jr.; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An electrochemical cell for measuring concentrations of metal ions comprises a sampling enclosure including a working electrode. a reference electrode. and a counter electrode. Ports are provided in the sampling enclosure for the introduction and removal of a liquid sample. an auxiliary reagent. and a standard solution. A stirring mechanism maintains a uniform composition of the liquid sample during operation of the cell. The electrochemical cell is operated by introducing ... |
|
| The Stability of Arc Attachment in Arcjet Propulsion Devices |
JAN 97 |
93 pages |
| Authors:
Mark A. Cappelli; Benjamin Yuan; STANFORD UNIV CA DEPT OF MECHANICAL ENGINEERING
|
| The design of high current plasma devices such as arcjet thrusters, arc heaters, magnetohydrodynamic generators, and plasma opening switches has in the past been based mostly on empirical methods. In the case of arcjet thrusters, these methodologies have produced a steady, reliable device when operated at low power levels. However, it is desirable to increase the performance and operating range of the arcjet so that they may run more efficiently ... |
|
| State-to-State Reactive and Collisional Dynamics of Atmospheric Species |
NOV 96 |
16 pages |
| Authors:
David J. Nesbitt; COLORADO UNIV AT BOULDER
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| The AFOSR research efforts over the past three years have achieved the following goals. (1) We have now completed state to state scattering measurements for CH4, H2O and HF with rare gas (Ar, Ne and He) collision partners, based on direct infrared absorption in crossed molecular beams. (2) Hot atom state to state scattering of Cl with HCl has been studied using high resolution Dopplerimetric techniques to obtain both differential ... |
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| State-to-State Reactive and Collisional Dynamics of Atmospheric Species |
SEP 96 |
12 pages |
| Authors:
David J. Nesbitt; COLORADO UNIV AT BOULDER
|
| The AFOSR/AASERT research efforts over the past three years (12/93-9/ 96) have achieved the following goals. (1) We have now completed state-to-state scattering measurements for CH4, H2O and HF with rare gas (Ar, Ne and He) collision partners, based on direct infrared absorption in crossed molecular beams. (2) Hot atom state-to-state scattering of Cl with HCl has been studied using high resolution Dopplerimetric techniques to obtain both differential and total ... |
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| Equipment for Selected Energy Epitaxial Deposition (SEED) |
AUG 96 |
12 pages |
| Authors:
I. S. Tsong; E. Bauer; R. B. Doak; ARIZONA STATE UNIV TEMPE
|
| We have constructed two Selected Energy Epitaxial Deposition (SEED) systems for the growth of wide bandgap semiconductors, specifically GaN and SiC. The first system is a seeded beam supersonic free-jet (SSJ) which will eventually be interfaced directly to our existing low-energy electron microscope (LEEM) to conduct in situ observations of the growth of epitaxial layers of GaN in real time. A beam intensity of 2 x 10 to the 19th ... |
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