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Results for “Pulse shaping”

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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

The UHURU X-ray instrument.

On Dec. 12, 1970, the UHURU X-ray observatory was launched into equatorial orbit with the prime mission of conducting an all-sky survey of astronomical X-ray sources with intensities of 0.00005 Sco-X1 or greater. The X-ray detection system contains 12 gas-filled proportional counters, 6 behind each collimator. The aspect system is discussed together with the structure, the pulse height analyzer, the command system, the calibration system, and the power distribution system. Pulse shape discrimination circuits used on UHURU use the same technique that was used on the system originally developed for large area proportional counters described by Gorenstein and Mickiewicz (1968).

Jagoda, N.↗
NASA NTRS1972

Response of TlCl /I,Be/ crystals to energetic ionizing radiation.

The response of a 3.8-cm TlCl(I,Be) crystal to 8 GeV negative pions is reported. A comparison is also made with the response of a similar CsI(Tl) crystal to the same incident radiation. In addition, the pulse shape and resolution characteristics of a 7.6-cm TlCl(I,Be) crystal, excited by positrons in the energy range 50 to 130 MeV, are reviewed. It is concluded that thallous chloride shows promise of being an excellent scintillating material for the detection and energy determination of high energy photons and charged particles.

Farukhi, M. R.↗
NASA NTRS1972

Artificial laser intensity oscillations associated with beam splitters.

Investigation of the interference-fringe jitter, due to wavelength instability in a laser, that gives rise to pulse-shape blurring intensity variations. The obtained results suggest that the problem can be controlled by using a perfectly flat splitter, or more easily by using a large-angle wedged splitter that either casts many fringes upon the detector element or casts none if the detector is sufficiently far from the splitter.

Kuehn, D. M.↗
NASA NTRS1972

Response of a seat-passenger system to impulsive loading.

This paper presents a summary of a study of the dynamic response of an aircraft seat-passenger system to impulsive loading typical of aircraft crash situations. A brief description of the computer model SIMULA is presented, and selected data from 305 separate cases which have been studied are discussed. Maximum system forces, displacements, velocities, and accelerations are presented as functions of velocity change, aircraft deceleration, crash pulse shape, passenger weight, and seat belt slack. Data from both single and coupled parameter studies are included. A correlation of SIMULA results with experimentally obtained data is made.

Collins, J. A.↗
NASA NTRS1972

Explosive shock damage potential in space structures

The effects of a pulse shape on the transient response of a cylindrical shell are presented. Uniaxial, membrane, and bending theories for isotropic shells were used in this study. In addition to the results of the analytical study, the preliminary results of an experimental study into the generation and measurement of shear waves in a cylindrical shell are included.

Mortimer, R. W.↗
NASA NTRS1973

Si(Li) position sensitive detector

A position sensitive detector was made using the lithium diffused layer of a lithium-drifted-silicon detector as the uniform resistive layer. An expression is derived for estimating the resistance from the thickness of the lithium layer. Expressions for the noise and ballistic deficit for single differentiation-double integration pulse shaping are presented. Room temperature data for a 1 Mev proton beam on a 45 mm long detector shows that the linearity is better than .05% and that the position resolution is 1.06 + or - .05 mm.

Gigante, J. R.↗
NASA NTRS1973

A position-sensitive X-ray detector for the HEAO-A satellite.

A position-sensitive, low-energy proportional counter system is described which will be used on the High-Energy Astronomical Observatory, Mission A, spacecraft. The associated system incorporates the capability to employ pulse-shape discrimination for background rejection and interpolation circuitry to locate the centroid of an X-ray event with an accuracy of approximately one eighth the cathode-wire spacing.

Held, D.↗
NASA NTRS1973

Pulsar detections at frequencies of 8.4 and 15.1 GHz.

Eleven pulsars were observed and five were detected at 15.1 GHz. Several exhibit strong scintillations at 8.4 GHz. Estimates are made of the spectral indices of five pulsars. Average pulse shapes are presented for the stronger signals.

Downs, G. S.↗
NASA NTRS1973

Further X-ray observations of Hercules X-1 from Uhuru.

Recent data are presented concerning the X-ray source Hercules X-1. Details of the 1.24-sec pulse shape and its variability are shown. The 1.24-sec period is observed to decrease with time, with an overall change of 4.5 microsec between January and July 1972. The X-ray intensity shows regular on states lasting 11 or 12 days followed by 24-day off states. While the source turn-on is not strictly periodic, the shape of the on state can be used to determine a period of 34.88 plus or minus 0.12 days for this cycle. The source turn-ons are found to only occur at one of two well-defined phases in the 1.7-day orbit.-

Giacconi, R.↗
NASA NTRS1973

Sensitivity of optimal control systems with bang-bang control.

The effects of small parameter variations on the performance index of optimal control systems with initial and final target manifolds, free end time, and bang-bang control are analyzed in this paper. A new approach to the sensitivity equation is presented. This approach takes into account the pulse-shaped variation produced by the parameter change on the bang-bang control. An expression, that relates the variations of the performance index, the trajectory, the final time, and the parameter, is derived. This expression extends to the class of optimal systems with bang-bang control, a result previously obtained by Courtin and Rootenberg (1971).

Rootenberg, J.↗
NASA NTRS1974

The Apollo X-ray fluorescence spectrometer

The Apollo X-ray fluorescence spectrometer was a part of a geochemical package flown on the Apollo 15 and 16 missions. The device was to map the concentrations of aluminum, magnesium, and silicon in the lunar regolith along the spacecraft ground track. A functional description of the spectrometer is given and the telemetry data format is discussed together with the pulse height analyzer, the pulse shape discriminator, questions of in-flight calibration, and the flight results.

Jagoda, N.↗
NASA NTRS1975

Lunar motion analysis

The results of raw data tapes on lunar motion recorded at McDonald Observatory from January 1 through June 30, 1975 are presented. The direct use of laser pulse shape information in the filtering of return photon data is suggested, together with an extensive revision of the environment record. The absence of archive parameters, including clock epoch offset, atmospheric seeing, and shot-by-shot resolution is noted. Programming problems involving photoelectric occultation observations are also examined.

Mulholland, J. D.↗
NASA NTRS1976

Ames collaborative study of cosmic ray neutrons

The results of a collaborative study to define both the neutron flux and the spectrum more precisely and to develop a dosimetry package that can be flown quickly to altitude for solar flare events are described. Instrumentation and analysis techniques were used which were developed to measure accelerator-produced radiation. The instruments were flown in the Ames Research Center high altitude aircraft. Neutron instrumentation consisted of Bonner spheres with both active and passive detector elements, threshold detectors of both prompt-counter and activation-element types, a liquid scintillation spectrometer based on pulse-shape discrimination, and a moderated BF3 counter neutron monitor. In addition, charged particles were measured with a Reuter-Stokes ionization chamber system and dose equivalent with another instrument. Preliminary results from the first series of flights at 12.5 km (41,000 ft) are presented, including estimates of total neutron flux intensity and spectral shape and of the variation of intensity with altitude and geomagnetic latitude.

Hewitt, J. E.↗
NASA NTRS1975

Strong scintillations in astrophysics. II - A theory of temporal broadening of pulses

A theory of temporal broadening of pulses propagating in a turbulent medium is developed on the basis of the Markov approximation. The theory may be applied to quite general turbulence spectra and to thin or thick turbulent regions. Since the basis of the theory is the wave equation, no reliance is placed on geometrical optics and no assumptions are made about the scattered angular spectrum. The observed smearing is found to be the combination of three effects: the dispersion effect, the pure refractive effect, and the diffraction effect. The last of these dominates for typical pulsar parameters. Pulse shapes are calculated for both Gaussian and Kolmogorov turbulence spectra and it is shown how these scale with the various turbulence parameters.

Lee, L. C.↗
NASA NTRS1977

X-ray spectra of Hercules X-1. 2: Intrinsic beam

The X-ray spectrum of Hercules X-1 was observed in the energy range 2-24 keV with sufficient temporal resolution to allow detailed study of spectral correlations with the 1.24 sec pulse phase. A region of spectral hardening which extends over approximately the 1/10 pulse phase may be associated with the underlying beam. The pulse shape stability and its asymmetry relative to this intrinsic beam are discussed.

Pravdo, S. H.↗
NASA NTRS1976

Magnetostrictive ultrasonic probes

The principles underlying the design and use of magnetostrictive ultrasonic probes is illustrated by oscillograms and sketches. Attention is given to such concepts as magnetostrictive transduction, broadband pulse shaping, guided wave propagation, wave impedance, reflection, transmission, and attenuation coefficients, coupling methods, and impulse-induced resonance. A number of applications of such probes are discussed including the measurement of elastic moduli, temperature, and acoustic emission and resonance studies.

Lynnworth, L. C.↗
NASA NTRS1977

The HEAO-A Scanning Modulation Collimator instrument

The Scanning Modulation Collimator X-ray instrument for the HEAO-A satellite was designed to measure celestial radiation in the range between 1 and 15 KeV and to resolve, and correlate, the position of X-ray sources with visible light sources on the celestial sphere to within 5 arc seconds. The positional accuracy is made possible by mechanical collimation of the X-ray sources viewed by the instrument. High sensitivity is provided from two systems each containing four gas filled proportional counters followed by preamplification, signal summing, pulse height analysis, pulse shape discrimination, X-ray event accumulators and telemetry processing electronics.

Roy, A.↗
NASA NTRS1977

Spectrally efficient modulation

Spectrally efficient modulation, involving the maximization of the transmitted data rate through a specified bandwidth, may aid in alleviating the problem of spectral congestion in the electromagnetic spectrum. Attention is given to pulse-shaping and nonbinary modulation, and particularly to combined amplitude- and phase-modulation. Theoretical performance limits, such as Shannon's bound, are used to assess the effectiveness of the systems described. Consideration is also allotted to spectrally efficient modulation for terrestrial microwave systems, required to provide 1000 voice channels in the 4- and 6-GHz band.

Smith, J. G.↗