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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Atmospheric interactions detected in both the upper and the lower chambers at Chacaltaya

The cosmic ray interactions in the energy region 10 to the 13th power to 10 to the 17th power eV were studied by emulsion chambers exposed at Chacaltaya, 5220 m above sea-level. The chambers have a two-storied structure, and the events observed in both chambers give important informations on these phenomena. The first Centauro event was detected as a small shower at the bottom of the upper chamber and as a big fraction of energy deposit in the lower chamber, which indicates a high contribution of hadronic showers. Results of the events with continuation in the rather low energy region are described.

Amato, N. M.↗
NASA NTRS1985

Size distributions of air showers accompanied with high energy gamma ray bundles observed at Mt. Chacaltaya

Size distributions of air showers accompanied with bundle of high energy gamma rays and/or large size bursts under emulsion chambers, to study the composition of primary cosmic rays and also characteristics of high energy nuclear interaction. Air showers initiated by particles with a large cross section of interaction may develop from narrow region of the atmosphere near the top. Starting levels of air showers by particles with smaller cross section fluctuate in wider region of the atmosphere. Air showers of extremely small size accompanied with bundle of gamma rays may be ones initiated by protons at lower level after penetrating deep atmosphere without interaction. It is determined that the relative size distribution according to the total energy of bundle of gamma rays and the total burst size observed under 15 cm lead absorber.

Matano, T.↗
NASA NTRS1985

Gamma-hadron families and scaling violation

For three different interaction models we have simulated gamma-hadron families, including the detector (Pamir emulsion chamber) response. Rates of gamma families, hadrons, and hadron-gamma ratios were compared with experiments.

Gaisser, T. K.↗
NASA NTRS1985

Mini-clusters

Experimental results of mini-clusters observed in Chacaltaya emulsion chamber no.19 are summarized. The study was made on 54 single core shower upper and 91 shower clusters of E(gamma) 10 TeV from 30 families which are visible energy greater than 80 TeV and penetrate through both upper and lower detectors of the two-story chamber. The association of hadrons in mini-cluster is made clear from their penetrative nature and microscopic observation of shower continuation in lower chamber. Small P sub t (gamma) of hadrons in mini-clusters remained in puzzle.

Chinellato, J. A.↗
NASA NTRS1985

Extremely high energy hadron and gamma-ray families(3). Core structure of the halo of superfamily

The study of the core structure seen in the halo of Mini-Andromeda 3(M.A.3), which was observed in the Chacaltaya emulsion chamber, is presented. On the assumption that lateral distribution of darkness of the core is exponential type, i.e., D=D0exp(-R/r0), subtraction of D from halo darkness is performed until the cores are gone. The same quantity on cores obtained by this way are summarized. The analysis is preliminary and is going to be developed.

Yamashita, S.↗
NASA NTRS1985

Intensities of high-energy cosmic rays at Mount Kanbala

General features of family events with Summary E sub gamma 200 TeV, observed by the emulsion chambers at Mt. Kanbala, are presented in comparison with the Monte Carlo simulation. The lateral and cluster structure, and the energy spectra of constituent gamma-rays and hadrons are shown to be consistent with the Monte Carlo results calculated under the assumption of heavy-enriched primary, scaling, QCD jets and increasing cross-section.

Ren, J. R.↗
NASA NTRS1985

On method of muon spectrum measurements by the scintillation detectors of a large thickness T4t sub o

Various methods for the study of muon spectrum are presented. The direct ones include the muon energy measurements by magnetic spectrometers. The indirect ones deal with the reconstruction of the muon spectrum from the spectrum of secondary particles obtained by burst or calorimeter technique. The burst technique is based on the measurement of the number of cascade particles, mainly in the cascade maximum, by the detectors of small thickness T sub 0. The calorimeter method consist in determination of the cascade energy with help of the cascade curve shape. The multilayer detectors are used for this purpose. They are usually comprised of proportional counters, X-ray emulsion chambers or scintillation counters with the target material placed between them. The scintillation detectors of a large thickness measures the total cascade energy directly and the detector works as a true calorimeter. When the total energy is detected, the cascade spectrum differs from the muon one.

Ryazhskaya, O. G.↗
NASA NTRS1985

Detection threshold energy of high energy cascade showers using thermoluminescence PTFE-sheet and hot-gas reader

A new thermoluminescence (TL) sheet was developed as a detector for high energy components in air showers. For the investigation of detection threshold energy for a cascade showeer, TL sheets were exposed at Mt. Fuji with X ray films in emulsion chambers and were scanned by a hot-gas reader. It is concluded that if a gamma ray whose energy is more than 6 TeV enters vertically into lead chambers, the resulting cascade shower is readily detectable at maximum development.

Kino, S.↗
NASA NTRS1985

Undercooling, Remelting, and Coarsening

Solidification of metal alloys with initial high undercoolings occurs with rapid recalescence due to rapid heat release of the latent heat of fusion. The recalescence temperature is usually higher than the solidus and/or the thermodynamic T sub o temperature of the alloy, depending on the initial undercooling and alloy composition. The rapid heating during recalescence alters the initially solidified structures, in ways that must include partial remelting, ripening, coarsening, and decomposition of the rapidly solidified primary metastable or supersaturated phases. New ways to study the solidification and remelting phenomena associated with the rapid heating during recalescence of undercooled alloys were developed. The phenomena are studied by using: (1) emulsions of iron and nickel base alloys in viscous liquid carriers; and (2) rapid heating of metal samples by electric discharge, using a technique similar to the exploding wire process (EWP), except with less power input. Experimental results are combined with theoretical analyses to better understand the solidification of levitated metal droplets with high undercooling, which relates to the solidification process.

Flemings, M. C.↗
NASA NTRS1985

Impurity Extraction by Droplets

The goals are to model and to measure the phase equilibrium properties of a finely divided fluid containing a large number of chemically similar species. The objective is to develop an accurate, usable model for such phenomena as pollutant extraction of rain clouds, industrial separation in spray towers, and separation in emulsions. The project was designed as a hierarchy of complementary theoretical and experimental steps. A theory was developed to describe the segregation of complex impurities at the interface of a solvent. This phenomenon is important in phase behavior when a large fraction of molecules in a material are near an interface, the situation in a finely divided material. The theory will be modified to account for the effect of surface curvature on the surface tension. The study of mixtures differs from pure fluids not only because of the surface effects but also because composition differences between the droplet and the surrounding vapor can stabilize a droplet with respect to a bulk phase.

Morrison, G.↗
NASA NTRS1985

High dispersion observations of Epsilon Aur from Sept. 1982 to March 1983

Between September 1982 and March 1983 I obtained high dispersion spectra of epsilon Aur in selected regions using the Palomar 200-inch coude spectrograph and the Dominion Astrophysical Observatory 48-coude spectrograph. All spectra were taken with the 90-mm ITT image tube and IIa-D emulsion. Radial velocities are listed for the sodium D lines, KI lines, H alpha, and a few other features. While most of the sodium and potassium features are surely circumstellar there is certainly an interstellar component present. In the direction of epsilon Aur interstellar gas is seen mostly with radial velocities between +5 and +10 km s(-1). The sodium D lines and potassium lines show incipient resolution which may involve the interstellar components. The equivalent widths of the sodium and potassium lines are given. For potassium, blending with atmospheric O2 makes the line at lambda 7664 unmeasurable on the dates of these observations. The increase in equivalent widths already noted by Pathasarathy and Lambert is evident. Blending and partial resolution of the circumstellar and interstellar features may account for much of the velocity structure which is only partially discernable at the available resolution.

Wallterstein, G.↗
NASA NTRS1985

Undercooling and solidification behavior in the InSb-Sb system

Use of the droplet emulsion technique has been successful in studying the undercooling and crystallization behavior of Sb, InSb, and an InSb-Sb eutectic alloy. Both droplet size and imposed cooling rate were influential in controlling the extent of liquid undercooling. The droplet surface coating was of significant importance in determining the resultant solidification product structure through its effect on nucleation kinetics. The maximum undercooling for pure Sb was extended from 0.08 to 0.23 T sub m. While simple crushing techniques provided a dramatic increase in droplet undercooling over the bulk material, emulsification treatments both enhanced this undercooling and allowed successful formation of a metastable simple cubic Sb phase. This phase was stable to temperatures approaching the melting point. The simple cubic phase was detected in droplet samples processed using DTA, air and water quenching, and drop tube processing under a helium gas atmosphere. A deviation in the InSb parent ingot composition limited interpretation of the line compound results, however, emulsification techniques extended the undercooling of this material to 0.17 T sub L and provided a stable, protective surface coating for the droplets. Emulsification of the eutectic alloy was effective at producing various levels of undercooling from 0.1 to 0.2 T sub E. Microstructural examination revealed a normal-type eutectic structure in the undercooled droplets indicating that solidification occurred within the coupled zone and that this zone is somewhat symmetric about the eutectic composition.

Graves, J. A.↗
NASA NTRS1986

Fluidized-bed reactor modeling for production of silicon by silane pyrolysis

An ideal backmixed reactor model (CSTR) and a fluidized bed bubbling reactor model (FBBR) were developed for silane pyrolysis. Silane decomposition is assumed to occur via two pathways: homogeneous decomposition and heterogeneous chemical vapor deposition (CVD). Both models account for homogeneous and heterogeneous silane decomposition, homogeneous nucleation, coagulation and growth by diffusion of fines, scavenging of fines by large particles, elutriation of fines and CVD growth of large seed particles. At present the models do not account for attrition. The preliminary comparison of the model predictions with experimental results shows reasonable agreement. The CSTR model with no adjustable parameter yields a lower bound on fines formed and upper estimate on production rates. The FBBR model overpredicts the formation of fines but could be matched to experimental data by adjusting the unkown jet emulsion exchange efficients. The models clearly indicate that in order to suppress the formation of fines (smoke) good gas-solid contacting in the grid region must be achieved and the formation of the bubbles suppressed.

Dudukovic, M. P.↗
NASA NTRS1986

Meson multiplicity versus energy in relativistic nucleus-nucleus collisions

A systematic study of meson multiplicity as a function of energy at energies up to 100 GeV/u in nucleus-nucleus collisions has been made, using cosmic-ray data in nuclear emulsion. The data are consistent with simple nucleon-nucleon superposition models. Multiplicity per interacting nucleon in AA collisions does not appear to differ significantly from pp collisions.

Atwater, T. W.↗
NASA NTRS1986

On the biological hazard of galactic antinuclei

The interaction of antinuclei in the galactic cosmic-ray beam with biological systems is studied. A nuclei-antinuclei annihilation event observed in nuclear emulsion near the end of the slowing-down trajectories of singly charged particle is discussed. An annihilation event that occurred by capture of the antinucleus into an atomic orbital followed by cascade to or near the ground atomic state and subsequent annihilation with the nuclear material of the atom is described. Microdosimetric quantities relevant to potential biological hazards are estimated. The average linear-energy-transfer spectrum for galactic cosmic ray antinuclei annihilation events in tissues is presented. It is observed that the annihilation in tissues occurs mainly in O and the heavier elements around K.

Wilson, J. W.↗