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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 127 records · Page 7
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NASA NTRS1974

Fluorescence and phosphorescence of photomultiplier window materials under electron irradiation

The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation were investigated using a Sr-90/Y-90 beta emitter as the electron source. Spectral emission curves of UV grade, optical grade, and electron-irradiated samples of MGF2 and LiF, CaF2, BaF2, sapphire, fused silica, and UV transmitting glasses were obtained over the spectral range of 200 nm to 650 nm. Fluorescence yields, expressed as the number of counts in a solid angle of 2 pi steradian per 1MeV of incident electron energy deposited, were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S-20) photocathodes, respectively.

Viehmann, W.↗
NASA NTRS1974

Analysis of the Vertical Temperature Profile Radiometer (VTPR) radiometric problem

Variations in bias radiation, on the detector as a function of scan mirror position, are reported for the VTPR instruments presently in orbit. Tests in the laboratory show that this bias radiation disappears when optical baffles are added. A detailed analysis explains quantitatively the observed bias variation which is due to the extraneous field-of-view of the detector, and the variation in magnitude of the far field-of-view solid angle as a function of mirror position.

Goldberg, I. L.↗
NASA NTRS1974

Photoelectric spectrophotometry of OQ 172 and OH 471

Absolute spectral energy distributions for the large-redshift quasars OQ 172 and OH 471 are discussed along with similar data for two other quasars: 4C 05.34 and PHL 957. If the redshift are assumed to be cosmological, OQ 172 and OH 471 are not as luminous as PHL 957. If these quasars are basically similar and if radiative processes dominate, the strength of alpha and the behavior of the continuum at the Lyman limit strongly suggest that these objects consist of a central ionizing source surrounded by discrete clouds, filaments, or a gaseous structure such as a disk. This gaseous matter does not cover the whole solid angle surrounding the source.

Oke, J. B.↗
NASA NTRS1974

Calculation of the effectiveness of a gamma telescope

A calculation is given of the effectiveness of recording of gamma quanta by a gamma telescope. Consideration of the isotropic nature of the stream of gamma quanta reaching the gamma telescope revealed that low energy gamma quanta are recorded relatively more effectively, since they are recorded from a wider solid angle than higher energy gamma quanta. The problem is solved of determining the effectiveness of recording of gamma quanta and determination of their energies by a gamma telescope.

Rylov, Y. A.↗
NASA NTRS1975

Upper limits to the quiet-time solar neutron flux from 10 to 100 MeV

The UCR large area solid-angle double scatter neutron telescope was flown to search for solar neutrons on 3 balloon flights on September 26, 1971, May 14, 1972 and September 19, 1972. The first two flights were launched from Palestine, Texas and the third from Cape Girardeau, Missouri. The float altitude on each flight was at about 5 g/sq cm residual atmosphere. Neutrons from 10 to 100 MeV were measured. No solar flares occurred during the flights. Upper limits to the quiet time solar neutron fluxes at the 95% confidence level are .00028, .00046, .00096 and .00090 neutrons/sq cm-sec in the energy intervals of 10-30, 30-50, 50-100 and 10-100 MeV, respectively.

Moon, S.↗
NASA NTRS1975

An experiment to measure cosmic ray 2H and 3He in the 4-10 GV range

It is known that the mean matter traversed by cosmic rays, X, can be obtained from the observed ratio of the flux of daughter nuclei to that of the parent nuclei provided X is much less than the attenuation mean free of the daughter nuclei. This condition is well satisfied in the case of 2H and 3He. We propose to measure the 2H/1H and 3He/4He ratios, using a multiwire proportional counter array and a superconducting magnet to measure the rigidity, and a set of aerogel Cerenkov counters to measure the velocity, thus yielding the mass of the particle. Results of a Monte-Carlo calculation based on actual experimental conditions are presented to show the resolution of the instrument. The area solid angle of the telescope is 90 sq cm sr with an average maximum detectable momentum of 140 GV.

Badhwar, G. D.↗
NASA NTRS1976

Upper limits to the quiet-time solar neutron flux from 10 to 100 MeV

A large-area solid-angle double-scatter neutron telescope was flown to search for solar neutrons on three balloon flights in 1971 and 1972. The first two flights were launched from Palestine, Texas, and the third from Cape Girardeau, Missouri. The float altitude on each flight was at about 5 g/sq cm residual atmosphere. Neutrons from 10 to 100 MeV were measured. No solar flares occurred during the flights. Upper limits to the quiet-time solar neutron fluxes at the 95-per cent confidence level are 2.8, 4.6, 9.6, and 9.0 x 10 to the -4th power neutron/sq cm/sec in the energy intervals of 10-30, 30-50, 50-100, and 10-100 MeV, respectively.

Moon, S.↗
NASA NTRS1976

Three-dimensional structure of the extended solar magnetic field and the sunspot cycle variation in cosmic ray intensity

A principal cause for the eleven-year sunspot cycle variation in the primary cosmic ray intensity observed at earth may be a variation in the solid angle of the heliosphere occupied by the extended solar polar magnetic field. Galactic cosmic rays have relatively easy access to the inner solar system through the regular extended solar polar fields, and relatively difficult access through the irregular extended solar sector structure fields.

Svalgaard, L.↗
NASA NTRS1975

A balloon-borne Ge/Li/ spectrometer for gamma-ray astronomy

On June 10, 1974, a new high-resolution gamma ray spectrometer operating in the energy range of 0.05 to 10 MeV was successfully balloon-flight tested. This system uses four 40 cu cm Ge(Li) crystals in a single cryostat as prime sensors. A 6.35 cm thick CsI (Na) shield provides background rejection and collimation, defining a solid angle of 0.095 sr. Cooling is provided by a liquid-nitrogen dewar. The system was highly stable with spectral resolution of better than 2.5 keV at 1 MeV for the flight duration. The background total count rate was about 20 counts/sec. Numerous lines were observed, most of which originated from secondary neutron interactions in the spectrometer. The sensitivity of the system to line emissions originating in cosmic point sources is 0.0001 to 0.001 photons per sq cm s over the energy range.

Jacobson, A. S.↗
NASA NTRS1976

Recent advances in birefringent filters

In the past several years, important developments have been made in the construction and theory of birefringent filters. Tunable filters that operate from 4500 to 7000 A with full widths at half maximum of 0.05 A and maximum transmissions of almost 20 percent have been constructed. Inexpensive large-aperture (at least 15 cm) achromatic waveplates have been fabricated which allow full use of resolution-solid angle products that are 100 times that of Fabry-Perots and 10,000 times that of grating systems.

Title, A. M.↗
NASA NTRS1977

The angular distribution of auroral kilometric radiation

A study based on data from Hawkeye 1, Imp 6 and Imp 8 satellites has shown that the intense kilometric radio emissions generated over the nightside auroral regions are beamed into a cone-shaped region whose axis of symmetry is tilted away from the magnetic axis of the earth, toward evenings, by about 20 deg. The solid angle of this emission cone increases systematically with increasing frequency, varying from about 1.1 sr at 56.2 kHz to about 3.5 sr at 178 kHz.

Green, J. L.↗
NASA NTRS1977

Structure of the iron fluorescence line in X-ray binaries

The paper presents an approximate solution to the iron K alpha line transfer problem in a stellar atmosphere illuminated by an external X-ray source as in a binary X-ray system. The emergent Comptonized line profile can independently yield information on the abundance of heavy elements in the primary atmosphere and on the solid angle subtended by the primary at the X-ray source.

Hatchett, S.↗
NASA NTRS1978

Theory of flux anisotropies in a guiding center plasma

The one particle distribution function f on the scale of the bounce motion of particles in a magnetic field B is considered. The Vlasov equation is expanded through O(epsilon) in the adiabatic parameter which is the ratio of particle gyroradius to scale length of the magnetic field. Because f is directly proportional to particle flux differential in kinetic energy and solid angle, f is in principle measurable in space experiments, and the analysis is tailored to be explicitly applicable to space problems. To O(1), f is gyrotropic; its first velocity moment is (if non-vanishing) parallel to B, and hence macroscopic parallel flow is included in this term. The O(epsilon) contribution is non-gyrotropic and macroscopic flow parallel to B plus additional parallel flow results from these terms. The degree of non-gyrotropy and the amount of cross-field macroscopic flow depend on the perpendicular component of the electric field, on curvature and shear in the magnetic field, and on the spatial gradient, pitch angle derivative, and speed derivative of the lowest order distribution function.

Birmingham, T. J.↗
NASA NTRS1978

Design and performance of a modularized NaI/Tl/ detector /The Crystal Ball prototype/

A prototype NaI(Tl) detector (the Cluster of 54) of spherical geometry subtending a solid angle of 7.5% of 4pi at its center, has recently been assembled and tested. This detector consists of 54 close-packed but optically isolated NaI(Tl) modules and the associated electronic circuitry. The Cluster of 54 is the predecessor of an almost complete spherical detector, the Crystal Ball, which will cover 94% of 4pi. The latter detector is now under construction and is especially designed for the study of gamma-rays produced in electron-positron collisions at colliding beam facilities. This article outlines the mechanical, optical, and electronic assembly of the prototype system.

Chan, Y.↗
NASA NTRS1978

Spectral irradiance standard for the ultraviolet - The deuterium lamp

A set of deuterium lamps is calibrated as spectral irradiance standards in the 200-350-nm spectral region utilizing both a high accuracy tungsten spectral irradiance standard and a newly developed argon mini-arc spectral radiance standard. The method which enables a transfer from a spectral radiance to a spectral irradiance standard is described. The following characteristics of the deuterium lamp irradiance standard are determined: sensitivity to alignment; dependence on input power and solid angle; reproducibility; and stability. The absolute spectral radiance is also measured in the 167-330-nm region. Based upon these measurements, values of the spectral irradiance below 200 nm are obtained through extrapolation.

Saunders, R. D.↗
NASA NTRS1978

Quadrispherical LEPEDEAS for ISEE's-1 and -2 plasma measurements

A new generation of spaceflight instrumentation for comprehensive measurements of plasmas within the earth's magnetosphere and its environs is described. These quadrispherical low energy proton and electron differential energy analyzers (LEPEDEAS) for the ISEE's-1 and -2 spacecraft are capable of determining the directional intensities of positive ions and electrons over all but 2 percent of the 4 pi sr solid angle for charged-particle velocity vectors at the spacecraft positions. The energy range of this instrumentation is E/Q of 1 eV to 45 keV with good energy and angular resolutions. An example of inflight observations within the earth's magnetosheath is presented.

Frank, L. A.↗
NASA NTRS1978

Radiative cooling in shock-heated hydrogen-helium plasmas

Axial and off-axis radiative cooling of cylindrical shock-heated hydrogen-helium plasmas is investigated theoretically and experimentally. The coupled fluid dynamic-radiative transfer equations are solved by a combination of approximation techniques aimed at simplifying the computation of the flux divergence term, namely, the quasi-isothermal approximation and the exponential approximation developed for the solid angle integration. The accuracy of the approximation schemes has been assessed and found acceptable for applying the methods to the rapid computation of the radiatively coupled flow problem. Radiative cooling experiments were conducted in a 6-inch annular arc accelerator shock tube (ANAA) for an initial pressure of 1 torr and shock speeds from 35 to 45 Km/sec. The results indicate that the lateral cooling is small compared with the axial cooling, and that better agreement is achieved between the data and the theoretical results by inclusion of the lateral temperature gradient.

Poon, P. T. Y.↗
NASA NTRS1978

A new concept for solar pumped lasers

A new approach is proposed in which an intermediate body heated by sunlight is used as the pumping source for IR systems, i.e., concentration solar radiation is absorbed and reradiated via an intermediate blackbody. This body is heated by focused sunlight to a high temperature and its heat losses are engineered to be small. The cooled laser tube (or tubes) is placed within the cavity and is pumped by it. The advantage is that the radiation spectrum is like a blackbody at the intermediate temperature and the laser medium selectively absorbs this light. Focusing requirements, heat losses, and absorption bandwidths of laser media are examined, along with energy balance and potential efficiency. The results indicate that for lasers pumped through an IR absorption spectrum, the use of an intermediate blackbody offers substantial and important advantages. The loss in radiative intensity for optical pumping by a lower-temperature body is partly compensated by the increased solid angle of exposure to the radiative environment.

Christiansen, W. H.↗