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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 NTRS1972

The geometric factor of a cylindrical plate electrostatic analyzer.

A method for calculating the geometric factor of cylindrical plate electrostatic energy analyzers with various detector geometries is described. The effects of the fringe field are estimated. For a special simple case an exact geometric factor is calculated, enabling an estimate to be made of the inaccuracies of the approximations used in other cases. The results of some calculations are presented, and a simple approximate expression for the geometric factor is deduced.

Johnstone, A. D.↗
NASA NTRS1973

Two-phase charge-coupled device

A charge-transfer efficiency of 99.99% per stage was achieved in the fat-zero mode of operation of 64- and 128-stage two-phase charge-coupled shift registers at 1.0-MHz clock frequency. The experimental two-phase charge-coupled shift registers were constructed in the form of polysilicon gates overlapped by aluminum gates. The unidirectional signal flow was accomplished by using n-type substrates with 0.5 to 1.0 ohm-cm resistivity in conjunction with a channel oxide thickness of 1000 A for the polysilicon gates and 3000 A for the aluminum gates. The operation of the tested shift registers with fat zero is in good agreement with the free-charge transfer characteristics expected for the tested structures. The charge-transfer losses observed when operating the experimental shift registers without the fat zero are attributed to fast interface state trapping. The analytical part of the report contains a review backed up by an extensive appendix of the free-charge transfer characteristics of CCD's in terms of thermal diffusion, self-induced drift, and fringing field drift. Also, a model was developed for the charge-transfer losses resulting from charge trapping by fast interface states. The proposed model was verified by the operation of the experimental two-phase charge-coupled shift registers.

Kosonocky, W. F.↗
NASA NTRS1978

Experiment definition and integration study for the accommodation of magnetic spectrometer payload on Spacelab/shuttle missions

A super-cooled magnetic spectrometer for a cosmic-ray experiment is considered for application in the high energy astronomical observatory which may be used on a space shuttle spacelab mission. New cryostat parameters are reported which are appropriate to shuttle mission weight and mission duration constraints. Since a super-conducting magnetic spectrometer has a magnetic fringe field, methods for shielding sensitive electronic and mechanical components on nearby experiments are described.

Buffington, A.↗
NASA NTRS1982

Pockels-effect cell for gas-flow simulation

A Pockels effect cell using a 75 cu cm DK*P crystal was developed and used as a gas flow simulator. Index of refraction gradients were produced in the cell by the fringing fields of parallel plate electrodes. Calibration curves for the device were obtained for index of refraction gradients in excess of .00025 m.

Weimer, D.↗
NASA NTRS1982

Automatic evaluation of interferograms

A system for the evaluation of interference patterns was developed. For digitizing and processing of the interferograms from classical and holographic interferometers a picture analysis system based upon a computer with a television digitizer was installed. Depending on the quality of the interferograms, four different picture enhancement operations may be used: Signal averaging; spatial smoothing, subtraction of the overlayed intensity function and the removal of distortion-patterns using a spatial filtering technique in the frequency spectrum of the interferograms. The extraction of fringe loci from the digitized interferograms is performed by a foating-threshold method. The fringes are numbered using a special scheme after the removal of any fringe disconnections which appeared if there was insufficient contrast in the holograms. The reconstruction of the object function from the fringe field uses least squares approximation with spline fit. Applications are given.

Becker, F.↗
NASA NTRS1989

Wide range magnetic electron spectrograph

An electron spectrogrpah is described that covers electron energies from 400 eV to 200 keV with an energy resolution of 10 percent. This overlaps the range of electrostatic deflection devices at low energy and solid state detectors at high energy. The spectrograph uses magnetic deflection of the electrons to achieve energy separation and images the full range of energies on a single plane. The magnetic circuit uses the fringing field of two axially located magnets to attain the large energy range. Six separate electron beams can be dispersed in the field, each entering the circuit from a different angle. This is a particular advantage when measuring plasma electron three-dimensional velocity distributions. The angular response of the instrument is particularly favorable and the stray magnetic field is sufficiently low to meet spacecraft requirements.

Coplan, M. A.↗
NASA NTRS1989

Characteristic impedance of microstrip lines

The dyadic Green's function for a current embedded in a grounded dielectric slab is used to analyze microstrip lines at millimeter wave frequencies. The dyadic Green's function accounts accurately for fringing fields and dielectric cover over the microstrip line. Using Rumsey's reaction concept, an expression for the characteristic impedance is obtained. The numerical results are compared with other reported results.

Bailey, M. C.↗
NASA NTRS1992

A program to study antiprotons in the cosmic rays: Arizona collaboration

The Cherenkov detector designed and built for the LEAP (Low Energy AntiProton) experiment utilized a novel design to achieve appreciable sensitive area (02. sq m) with a refractive index of 1.25 in a magnetic fringe field region (500-1000 Gauss). The weight was held to only 64 kg by using 16 unshielded Hamamatsu R2490-01 photomultiplier tubes, each aligned with its local magnetic field. A filling and reservoir system for the highly volatile FC-72 liquid Cherenkov radiator also presented many design challenges. Relativistic particles yielded about 72 photoelectrons, total.

Bowen, Theodore↗
NASA NTRS1993

On-line process analysis innovation: DiComp (tm) shunting dielectric sensor technology

The DiComp Shunting Dielectric Sensor (SDS) is a new patent-pending technology developed under the Small Business Innovation Research Program (SBIR) for NASA's Kennedy Space Center. The incorporation of a shunt electrode into a conventional fringing field dielectric sensor makes the SDS uniquely sensitive to changes in material dielectric properties in the KHz to MHz range which were previously detectable only at GHz measurement frequencies. The initial NASA application of the SDS for Nutrient Delivery Control has demonstrated SDS capabilities for thickness and concentration measurement of Hoagland nutrient solutions. The commercial introduction of DiComp SDS technology for concentration and percent solids measurements in dispersions, emulsions and solutions represents a new technology for process measurements for liquids in a variety of industries.

Davis, Craig R.↗
NASA NTRS1995

Full-Wave Analysis Of MMICs Using A Generalized Yee Algorithm

Improved method of temporal analysis of propagation of electro-magnetic waves in monolithic microwave integrated circuits (MMICs) implemented by generalized version of traditional Yee algorithm. Provides more accurate mathematical modeling for analysis and design of MMICs. Based on unstructured and otherwise irregular grids. Grids readily fitted to conductive and dielectric circuit elements having realistically complex three-dimensional shapes. Better for modeling important and geometrically complex phenomena like fringing fields.

Lansing, Faiza S.↗
NASA NTRS2004

Wide Angle Liquid Crystal Optical Phased Array

Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

Wang, Xing-Hua↗
NASA NTRS2006

Miniature Oxidizer Ionizer for a Fuel Cell

A proposed miniature device for ionizing the oxygen (or other oxidizing gas) in a fuel cell would consist mostly of a membrane ionizer using the same principles as those of the device described in the earlier article, Miniature Bipolar Electrostatic Ion Thruster (NPO-21057). The oxidizing gas would be completely ionized upon passage through the holes in the membrane ionizer. The resulting positively charged atoms or molecules of oxidizing gas could then, under the influence of the fringe fields of the ionizer, move toward the fuel-cell cathode that would be part of a membrane/electrode assembly comprising the cathode, a solid-electrolyte membrane, and an anode. The electro-oxidized state of the oxidizer atoms and molecules would enhance transfer of them through the cathode, thereby reducing the partial pressure of the oxidizer gas between the ionizer and the fuel-cell cathode, thereby, in turn, causing further inflow of oxidizer gas through the holes in the membrane ionizer. Optionally the ionizer could be maintained at a positive electric potential with respect to the cathode, in which case the resulting electric field would accelerate the ions toward the cathode.

Hartley, Frank↗
NASA NTRS2012

Photogrammetry Measurements During a Tanking Test on the Space Shuttle External Tank, ET-137

On November 5, 2010, a significant foam liberation threat was observed as the Space Shuttle STS-133 launch effort was scrubbed because of a hydrogen leak at the ground umbilical carrier plate. Further investigation revealed the presence of multiple cracks at the tops of stringers in the intertank region of the Space Shuttle External Tank. As part of an instrumented tanking test conducted on December 17, 2010, a three dimensional digital image correlation photogrammetry system was used to measure radial deflections and overall deformations of a section of the intertank region. This paper will describe the experimental challenges that were overcome in order to implement the photogrammetry measurements for the tanking test in support of STS-133. The technique consisted of configuring and installing two pairs of custom stereo camera bars containing calibrated cameras on the 215-ft level of the fixed service structure of Launch Pad 39-A. The cameras were remotely operated from the Launch Control Center 3.5 miles away during the 8 hour duration test, which began before sunrise and lasted through sunset. The complete deformation time history was successfully computed from the acquired images and would prove to play a crucial role in the computer modeling validation efforts supporting the successful completion of the root cause analysis of the cracked stringer problem by the Space Shuttle Program. The resulting data generated included full field fringe plots, data extraction time history analysis, section line spatial analyses and differential stringer peak ]valley motion. Some of the sample results are included with discussion. The resulting data showed that new stringer crack formation did not occur for the panel examined, and that large amounts of displacement in the external tank occurred because of the loads derived from its filling. The measurements acquired were also used to validate computer modeling efforts completed by NASA Marshall Space Flight Center (MSFC).

Littell, Justin D.↗
DOE OSTI2024

Investigating the origin of the far-field reflection interference fringe (RIF) of microdroplets

We show that the reflection interference fringe (RIF) is formed on a screen far away from the microdroplets placed on a prism-based substrate, which have low contact angles and thin droplet heights, caused by the dual convex–concave profile of the droplet, not a pure convex profile. The geometric formulation shows that the interference fringes are caused by the optical path difference when the reflected rays from the upper convex profile at the droplet–air interface interfere with reflection from the lower concave profile at oblique angles lower than the critical angle. Analytic solutions are obtained for the droplet height and the contact angle out of the fringe number and the fringe radius in RIF from the geometric formulation. Furthermore, the ray tracing simulation is conducted using the custom-designed code. The geometric formulation and the ray tracing show excellent agreement with the experimental observation in the relation between the droplet height and the fringe number and the relation between the contact angle and the fringe radius. This study is remarkable as the droplet's dual profile cannot be easily observed with the existing techniques. However, the RIF technique can effectively verify the existence of a dual profile of the microdroplets in a simple setup. In this work, the RIF technique is successfully developed as a new optical diagnostic technique to determine the microdroplet features, such as the dual profile, the height, the contact angle, the inflection point, and the precursor film thickness, by simply measuring the RIF patterns on the far-field screen.

42 ENGINEERING↗
DOE OSTI2022

Contributions to Dielectric Constant Enhancement in Thin Film Metal Insulator Metal Capacitors

Thin film metal-insulator-metal capacitors were fabricated with varying dielectric and electrode thicknesses and areas. Measurement of the dielectric properties of the capacitors consistently yielded higher than predicted capacitance values, which prompted the exploration of three factors that could enhance the capacitance. Modeling of the fringing capacitance and field enhancement due to the capacitor geometry, both yield capacitance gains, albeit insufficient to fully explain the observed behavior. The possible role of changes in polarizability of the dielectric film constituents, due to the amorphous nature of the films was also evaluated, but the results of the investigation of this contribution were inconclusive. Herein, the role of accumulation/depletion layers on capacitance enhancement was also analyzed. For capacitors fabricated with thinner dielectrics, the presence of these layers can effectively reduce the dielectric thickness, resulting in contributions to capacitance that are significant. The calculations completed suggest these contributions may be more important than fringing field contributions. Additional studies of these mechanisms are in progress.

36 MATERIALS SCIENCE↗
NASA NTRS1992

The polarization electric field and its effects in an anisotropic rotating magnetospheric plasma

Spatial variations of density and temperature along a magnetic field line are evaluated for a plasma undergoing adiabatic motion in a rotating magnetosphere. The effects of centrifugal and gravitational forces are accounted for, as is anisotropy in the pitch angle distribution functions of individual species. A polarization electric field is invoked to eliminate the net electric charge density resulting from the aforementioned mass dependent forces and different anisotropies. The position of maximum density in a two-component, electron-ion plasma is determined both in the absence and in the presence of the polarization effect and compared. A scale height, generalized to include anisotropies, is derived for the density fall-off. The polarization electric field is also included in the parallel guiding center equation; equilibrium points are determined and compared in both individual and average senses with the position of density maximum. Finally a transverse (to magnetic field lines) electric component is deduced as a consequence of dissimilar charge neutralization on adjacent field lines. The E x B velocity resultant from such a 'fringing' electric field is calculated and compared with the magnitude of other drifts.

Huang, T. S.↗
DOE OSTI2025

Interference fringe (IF) technique for droplet contact angle and thickness measurements: Ultralow contact angle and nanoscale thickness measurement

Recently, reflection interference fringe (RIF) and transmission fringe (TIF) techniques have been introduced to investigate the origin of far-field interference fringe (IF) formation and to determine a droplet's contact angle and thickness by measuring the fringe radius. In this study, characteristics of the IF technique are analyzed based on the RIF and TIF by varying the schematics, such as configuration (transmission/reflection), the droplet's side (left-hand side/right-hand side), and the substrate types (flat/prism). The analysis also investigates the refraction effect at the droplet edge and the maximum incidence and contact angles. The schematic variation shows that the widest contact angle range can be measured in a transmission configuration with droplet's right-hand side, and that the fringe radius decreases with incidence angles on a prism substrate, consistent with the recent observation. Refraction at the droplet edge causes the fringe radius to increase or decrease depending on the degree of refraction. Based on the characteristics study, it is revealed that the IF technique can determine nanometer-scale thicknesses below 100 nm on droplets, corresponding to ultra-small contact angles of less than 0.01°, with an extended working distance of 3000 mm and an optimized incidence angle, assuming a spherical profile. This finding is significant, as it demonstrates that the nanoscale thickness can be determined in situ under ambient conditions using a simple optical configuration, without requiring a sophisticated setup, such as a microscope. It is anticipated that the IF technique can be combined with other nanoscale thickness measurement techniques to enhance its measurement reliability.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Transmission interference fringe ( TIF ) technique for the dynamic visualization of evaporating droplet

Here, the transmission interference fringe (TIF) technique was developed to visualize the dynamics of evaporating droplets based on the Reflection Interference Fringe (RIF) technique for micro-sized droplets. The geometric formulation was conducted to determine the contact angle (CA) and height of macro-sized droplets without the need for the prism used in RIF. The TIF characteristics were analyzed through experiments and simulations to demonstrate a wider range of contact angles from 0 to 90°, in contrast to RIF's limited range of 0–30°. TIF was utilized to visualize the dynamic evaporation of droplets in the constant contact radius (CCR) mode, observing the droplet profile change from convex-only to convex-concave at the end of dry-out from the interference fringe formation. The TIF also observed the contact angle increase from the fringe radius increase. This observation is uniquely reported as the interference fringe (IF) technique can detect the formation of interference fringe between the reflection from the center convex profile and the reflection from the edge concave profile on the far-field screen. Unlike general microscopy techniques, TIF can detect far-field interference fringes as it focuses beyond the droplet-substrate interface. The formation of the convex-concave profile during CCR evaporation is believed to be influenced by the non-uniform evaporative flux along the droplet surface.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗