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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Analysis of flight effects on noise radiation from jet flow using a convecting quadrupole model

The effects of flight on noise radiation from convecting quadrupoles in a jet flow are examined. The analysis shows that as flight velocity increases there is a steadily increasing amplification of the sound that is radiated into the forward arc and a large reduction of the sound that is radiated into the rearward arc. The analysis also shows the same trend when there is a reduction in the exhaust velocity with, however, a further rise in amplification in the forward quadrant and a drop in attenuation in the aft quadrant. Finally, it is concluded that there is a transmission effect tending to enhance the sound radiation by a density ratio pf/pj which increases with increasing jet temperature.

Dash, R.↗
NASA NTRS1978

Nuclear quadrupole resonance studies project

The participation of undergraduates in nuclear quadrupole resonance research at Grambling University was made possible by NASA grants. Expanded laboratory capabilities include (1) facilities for high and low temperature generation and measurement; (2) facilities for radio frequency generation and measurement with the modern spectrum analyzers, precision frequency counters and standard signal generators; (3) vacuum and glass blowing facilities; and (4) miscellaneous electronic and machine shop facilities. Experiments carried out over a five year period are described and their results analyzed. Theoretical studies on solid state crystalline electrostatic fields, field gradients, and antishielding factors are included.

Murty, A. N.↗
NASA NTRS1979

Dipole and quadrupole synthesis of electric potential fields

A general technique for expanding an unknown potential field in terms of a linear summation of weighted dipole or quadrupole fields is described. Computational methods were developed for the iterative addition of dipole fields. Various solution potentials were compared inside the boundary with a more precise calculation of the potential to derive optimal schemes for locating the singularities of the dipole fields. Then, the problem of determining solutions to Laplace's equation on an unbounded domain as constrained by pertinent electron trajectory data was considered.

Tilley, D. G.↗
NASA NTRS1979

The performance of primary Cs beam clocks using quadrupole and hexapole deflection systems. Consequences for time keeping

Since 1978 the time-and-frequency standard CS1 of the Physikalisch-Technische Bundesanstalt (PTB) has operated continuously as a 'primary clock'. Its uncertainty (7.1 to the negative 15th power) is considerably smaller than that of the other existing primary standards. The CS1 is equipped with a combination of quadrupole and hexapole magnets and uses a longitudinal C-field. Consequences of utilizing primary clocks of this quality for the generation of the International Atomic Time Scale TAI are discussed.

Becker, G.↗
NASA NTRS1980

Measurements of the H2 4-0 quadrupole bands of Uranus and Neptune

It is found that the equivalent widths of the lines of the 4-0 H2 quadrupole band on Uranus and Neptune are substantially smaller than the values found by some previous observers. An analysis of the results based on a range of atmospheric models yields H2 abundances of 240 + or - 60 km-amagats for Uranus and greater than approximately 200 km amagats for Neptune.

Smith, W. H.↗
NASA NTRS1980

Gravitational radiation quadrupole formula is valid for gravitationally interacting systems

An argument is presented for the validity of the quadrupole formula for gravitational radiation energy loss in the far field of nearly Newtonian (e.g., binary stellar) systems. This argument differs from earlier ones in that it determines beforehand the formal accuracy of approximation required to describe gravitationally self-interacting systems, uses the corresponding approximate equation of motion explicitly, and evaluates the appropriate asymptotic quantities by matching along the correct space-time light cones.

Walker, M.↗
NASA NTRS1980

Interference with negative particle sampling due to formation of positive ions in a quadrupole mass spectrometer

A quadrupole mass spectrometer has been utilized to study active discharges containing Cs vapor. Production of positive ions by electron impact within the mass spectrometer and subsequent secondary electron emission from cesiated surfaces produced spurious or pseudonegative ion signals which interfered with attempts to sample negative ions from the plasma. These effects may also occur in other gas discharge systems.

Kuehn, D. G.↗
NASA NTRS1982

Quadrupole distortions of the heliospheric current sheet in 1976 and 1977

Latitudinal variations in the position of the heliospheric current sheet were investigated using interplanetary measurements from Helios A, Helios B, IMP 8, and white light corona measurements in the period May 1976 to May 1977. The latitude of the heliospheric current sheet between 0.3 AU and I AU is consistent with that of the maximum brightness curve of white light polarization brightness at 1.75 solar radii within approximately + or - 7 deg. The combined data sets show that the four-sector magnetic sector pattern observed in the ecliptic plane for most of this epoch could be attributed to a warped current sheet whose shape near the sun resembles a saddle surface that is nearly symmetrical about the equatorial plane. The latitudinal extent of the current sheet is on the average 8 deg and the maximum extent is 15 deg (except on one rotation, when it is 20 deg). These results can be interpreted as a consequence of the solar magnetic field, the dominant components of the field being due to a dipole nearly aligned with the sun's spin axis and a quadrupole component whose strength is about 17 percent of the dipole.

Bruno, R.↗
NASA NTRS1983

Desaturation of H2 quadrupole lines in the atmospheres of the outer planets

The vibrational dependence of self-broadening of molecular hydrogen lines results in a desaturation of quadrupole absorption lines long thought to be highly saturated in planetary atmospheres. This desaturation significantly alters H2 abundances in the atmospheres of Uranus and Neptune. Baseline models are presented to illustrate the effects of the revision of this fundamental H2 parameter.

Cochran, W. D.↗
NASA NTRS1986

The quadrupole ionosphere

The principal features that might exist in the terrestrial paleoionosphere, if the geomagnetic field were to assume a quadrupole form during a polarity reversal are discussed. Complicated phenomena would be expected to occur at magnetic equators and magnetospherically-driven plasma convection might occur at latitudes where the magnetic field is steeply inclined. The influence of magnetic field strength on ionospheric structure is considered in general terms.

Rishbeth, H.↗
NASA NTRS1986

The ortho-para H2 distribution on Uranus: Constraints from the collision-induced 3-0 dipole band and 4-0 S(0) and S(1) quadrupole line profiles

Recent high quality spectral observations have allowed the derivation of constraints on the atmospheric structure of Uranus. The present analysis, which is based on the detailed modeling of a broadband geometric albedo spectrum and high resolution observations of the H2 4-0 quadrupole and 6818.9-A CH4 features, yields (1) a family of models which parameterize an upper tropospheric haze layer, (2) a lower, optically infinite cloud at a given pressure level, (3) the cloud-level methane molar fraction, and (4) the mean ortho/para ratio in the visible atmosphere. The single scattering albedo of atmospheric aerosols exhibits a steep darkening between 5890 and 6040 A.

Baines, K. H.↗
NASA NTRS1986

Quadrupole mass spectrometer for Space Shuttle applications - Flight capabilities and ground calibration

The AFGL Quadrupole Ion/Neutral Mass Spectrometer (QINMS), its flight capabilities, and a few examples of QINMS data from the STS-4 flight are discussed in addition to the beam facility and calibration procedures used at the Los Alamos National Laboratory facility. A 5-eV atomic oxygen beam is produced using a continuous optical discharge technique, and the resulting pumped beam has sufficient high flux and velocity to simulate orbital conditions. The calibrated instrument will be used in the NASA Johnson Space Center Evaluation of Oxygen Interactions with Materials experiment to measure the density of ambient oxygen and to identify the products of oxygen-surface reactions.

Hunton, D. E.↗
NASA NTRS1987

Uranus' (3-0) H2 quadrupole line profiles

Spectra of Uranus' S3(0) and S3(1) H2 quadrupole lines, obtained during the 1978-1980 apparitions, are analyzed, and are found to require the presence of a deep cloud. Modifications of the Baines and Bergstralh (1986) standard model, including an additional haze layer above the 16-km-am H2 level which contains strongly absorbing particles, are needed to fit the observations. For a Rayleigh phase function, such a haze (uniformly mixed with the gas above this level) would have an absorption optical depth of 0.16 and a single scattering particle albedo of 0.30. This modification would imply a fraction of normal H2 equal to 0.25 + or - 0.10, in agreement with the Baines and Bergstralh standard model.

Trafton, L.↗
NASA NTRS1987

Research relative to an advanced rod control system for quadrupole mass spectrometry applications

The design of a suitable amplifier output stage using available transistors and passive components is summarized. All of the analysis and calculation confirm that it is feasible to design the amplifier and quadrupole coupling circuit needed for the Advanced Rod Control System. The progress obtained so far concerning the three frequency tank circuits to be used in the oscillator for the mass spectrometer of the Cometary Rendezvous Asteroid Flyby (CRAF) project is presented. Results from this study look promising. However, it is not known what minimum impedance levels are required to make it possible for the oscillator to work properly. Therefore, it is necessary to construct a prototype circuit in the laboratory which can be measured and tested in an oscillator circuit. Continued attempts will be made to develop a useful inductor motor with better characteristics than the one being used at the moment. It is important that such a model be found if computer simulation is to reflect reality more closely.

Carignan, George R.↗
NASA NTRS1988

A possible detection of Jupiter's northern auroral S1(1) H2 quadrupole line emission

An upper limit is presently determined for the mean intensity of the Jupiter northern Auroral UV/thermal hot spot's S1(1) H2 quadrupole emission, over an 8 sq arcsec illuminated beam; the value obtained is 4.2 X 10 to the -6th W/sq m per sr. It is suggested that the nonradiative deexitation of the H2 molecules via collisions with H may have been underestimated by Kim and Maguire (1986), due to uncertainties concerning auroral H density.

Trafton, L.↗
NASA NTRS1990

Development of a quadrupole-based Secondary-Ion Mass Spectrometry (SIMS) system at Lewis Research Center

The design, construction, and initial use of an ion microprobe to carry out secondary ion mass spectrometry (SIMS) of solid samples is reported. The system is composed of a differentially pumped custom-made UHV (Ultra High Vacuum) chamber, a quadrupole mass spectrometer and a telefocus A-DIDA ion gun with the capability of producing beams of Cesium, as well as inert and reactive gases. The computer control and acquisition of the data were designed and implemented using a personal computer with plug-in boards, and external circuitry built as required to suit the system needs. The software is being developed by using a FORTH-like language. Initial tests aimed at characterizing the system, as well as preliminary surface and depth-profiling studies are presently underway.

Vargas-Aburto, Carlos↗
NASA NTRS1991

Dynamics of charged particles in a Paul radio-frequency quadrupole trap

A molecular-dynamics simulation of hundreds of ions confined in a Paul trap has been performed. The simulation includes the trapped particles' micromotion and interparticle Coulomb interactions. A random walk in velocity was implemented to bring the secular motion to a given temperature which was numerically measured. When the coupling Gamma is large the ions from concentric shells which undergo a quadrupole oscillation at the RF frequency, while the ions within a shell form a 2D hexagonal lattice. Ion clouds at 5 mK show no RF heating for q(z) less than about 0.6, whereas rapid heating is seen for qz = 0.8.

Prestage, J. D.↗
NASA NTRS1991

Determination of absolute strengths of N2 quadrupole lines from high-resolution ground-based IR solar observations

The strength of S-branch lines of the N2 (1-0) electric quadrupole vibration-rotation band are determined by an analysis of solar absorption spectra. The solar data were recorded with a Fourier transform spectrometer and are characterized by high resolution, and a high signal-to-noise ratio. By extrapolating equivalent width measurements of the lines from varying air masses to zero air mass, the line strengths are found for the transitions from S7 to S10. The results presented do not include half widths and are found to be accurate to within 5 percent, and following a redetermination the N2 transitions are accurate to within 0.0002/cm. Line-of-sight atmospheric air masses associated with remotely sensed IR spectroscopic observations can be determined directly by utilizing the highly accurate data.

Demoulin, P.↗