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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Primary and secondary particle contributions to the depth dose distribution in a phantom shielded from solar flare and Van Allen protons

Calculations have been made using the nucleon-meson transport code NMTC to estimate the absorbed dose and dose equivalent distributions in astronauts inside space vehicles bombarded by solar flare and Van Allen protons. A spherical shell shield of specific radius and thickness with a 30-cm-diam. tissue ball at the geometric center was used to simulate the spacecraft-astronaut configuration. The absorbed dose and the dose equivalent from primary protons, secondary protons, heavy nuclei, charged pions, muons, photons, and positrons and electrons are given as a function of depth in the tissue phantom. Results are given for solar flare protons with a characteristic rigidity of 100 MV and for Van Allen protons in a 240-nautical-mile circular orbit at 30 degree inclination angle incident on both 20-g/sq cm-thick aluminum and polyethylene spherical shell shields.

Santoro, R. T.↗
NASA NTRS1972

A Review: Some biological effects of high LET radiations

There are qualitative and quantitative differences in the biological damage observed after exposure to high LET radiation as compared to that caused by low LET radiations. This review is concerned with these differences, which are ultimately reflected at the biochemical, cellular and even whole animal levels. In general, high LET radiations seem to produce biochemical damage which is more severe and possibly less repairable. Experimental data for those effects are presented in terms of biochemical RBE's with consideration of both early and late manifestations. An LET independent process by which significant biochemical damage may result from protons, neutrons and negative pion mesons is discussed.

Wiley, A., Jr.↗
NASA NTRS1972

Thermionic reactor power system: Effects of radiation on integration with Manned Space Station

The application of a thermionic reactor power system to the modular space station is described. The nominal net power is 40 kWe, with the power system designed to be applicable over the power range from 25 to 60 kWe. The power system is designed to be launched by the space shuttle. Radiation protection is provided by LiH neutron shielding and W gamma shielding in a shaped 4 pion configuration, i.e., the reactor is shielded on all sides but not to equal extent. Isodose contours are presented for the region around the modular space station. Levels and spectral distribution of radiation are given for later evaluation of effects on space station experiments. Parametric data on the effects of separation distance on power system mass are presented.

Gietzen, A. J.↗
NASA NTRS1972

Muon production

The production of muons by collisions of primary cosmic ray particles with air nuclei is discussed. From these collisions pions and kaons are produced which then decay into muons. Two cases, oblique incidence and vertical incidence, are analyzed theoretically. Theoretical calculations agree well with observed data.

Maeda, K.↗
NASA NTRS1972

Ultrahigh energy photons, electrons, and neutrinos, the microwave background, and the universal cosmic-ray hypothesis

The production of ultrahigh energy photons, electrons and neutrinos as the decay products of pions produced in photomeson interactions between cosmic ray nucleons and the blackbody microwave background is discussed in terms of the resultant energy spectra of these particles. Simple asymptotic formulas are given for calculating the ultrahigh energy photon spectrum predicted for the universal cosmic ray hypothesis and the resulting spectra are compared with those obtained previously by numerical means using a different propagation equation for the photons. Approximate analytic solutions for the photon spectra are given in terms of simple power-law energy functions and slowly varying logarithmic functions.

Stecker, F. W.↗
NASA NTRS1972

Energy calibration of a cosmic ray ionization spectrometer

The NASA/GSFC high energy cosmic ray experiment was calibrated during the summer of 1970 using protons and pions with energies from 9.3 GeV to 17.6 GeV. The best measure found for the energy E of an incoming primary particle is sigma I, the total number of ionizing particles observed in the instrument, summed over the various iron modules. The resolution in the calibration energy range is about + or - 30 percent (s.d.) over a wide range of incident angles and positions. The calibration function may be parameterized as e = sigma I/K, where K is predominantly a function of the location of the first interaction and the trajectory of the incoming particle.

Whiteside, H.↗
NASA NTRS1972

Calculation of the lunar photon albedo from galactic and solar proton bombardment.

The lunar photon albedo due to cosmogenic and primordial photon sources has been calculated. The individual photon leakage spectra from prompt photons produced by galactic cosmic ray (GCR) and solar cosmic ray (SCR) induced nuclear interactions, from the decay of GCR- and SCR-induced radionuclides, and from the decay of naturally occurring radionuclides are given. An approximate estimate of the leakage from the photon-electron cascade initiated by the decay of neutral pions is also given. Monte Carlo methods have been used to determine the nucleon-meson cascade, and discrete-ordinates methods were used for the photon and low-energy neutron transport.

Armstrong, T. W.↗
NASA NTRS1972

Balloon measurements of the energy spectrum of cosmic electrons between 1 and 25 GeV.

During three balloon flights made in 1966 and 1967, cosmic electrons were investigated with the aid of a hodoscope detector that provided extensive and detailed information on each cosmic-ray event triggering the apparatus. Similar information obtained during calibration exposures to protons and pions as well as to electrons was used to provide identification of cosmic electrons and to determine their energies. Differential primary electron intensities measured in the range from 1 to 25 GeV were substantially larger than some earlier measurements. In conjunction with existing measurements at energies above 100 GeV, this finding indicates that the energy spectrum of cosmic electrons is steeper than that of cosmic-ray nuclei and consequently suggests that Compton/synchrotron energy loss plays a significant role in shaping the electron spectrum.

Earl, J. A.↗
NASA NTRS1972

Pionic X-ray yields and 2p-level widths in Li6, Be9, C12 and O16.

Measurement of the intensities of 2p-1s pionic X-ray transitions in Li6, Be9, C12 and O16 by using an absolute-efficiency technique. Population probability predictions for the mesonic levels, and values for the strong-interaction levels widths are obtained by pion-cascade calculations. Numerical values are also obtained for the 2p-level absorption broadening.

Sapp, W. W., Jr.↗
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

Diffuse cosmic gamma rays: Present status of theory and observation

Positive diffuse gamma ray flux measurements now exist for energies up to the 100 MeV range. The totality of the observations in the 0.001 to 100 MeV range follow an E to the minus 2nd power trend in the differential isotropic photon spectrum but significant features appear. Possible theoretical interpretations of these features are discussed. New results on the diffuse flux from the galaxy substantiate the pion-decay origin hypothesis for gamma radiation above 100 MeV.

Stecker, F. W.↗
NASA NTRS1973

Ultrahigh Energy Gamma-rays

An analysis is made of the interactions of very high energy cosmic ray protons with the relict radiation in extragalactic space. Two situations are examined: gamma rays derived from neutral pions -mesons produced in collisions in a nonevolutionary situation and gamma rays from electron pairs produced at early epochs. It is shown that the ultrahigh energy gamma rays could conceivably be of high enough intensity to be detected. The flux of gamma rays from the second process is not far from the diffuse background that was reported.

Strong, A. W.↗
NASA NTRS1973

The Deuterium Puzzle in the Symmetric Universe

The examination of the experimental data concerning the reaction antiproton + He-4 yields pions + nuclei shows that the low abundance of D 2 can be explained only by assuming a low He abundance at the beginning of the radiative era. This is a completely independant confirmation of the evasion of neutrons (and antineutrons) from the emulsion before the end of the epoch where nucleogenesis might have taken place, and leads to an estimate of the size of the emulsion when T = 1 MeV.

Leroy, B.↗
NASA NTRS1973

Monte Carlo simulation of the nuclear-electromagnetic cascade development and the energy response of ionization spectrometers

Modifications to the basic computer program for performing the simulations are reported. The major changes include: (1) extension of the calculations to include the development of cascades initiated by heavy nuclei, (2) improved treatment of the nuclear disintegrations which occur during the interactions of hadrons in heavy absorbers, (3) incorporation of accurate multi-pion final-state cross sections for various interactions at accelerator energies, (4) restructuring of the program logic so that calculations can be made for sandwich-type detectors, and (5) logic modifications related to execution of the program.

Jones, W. V.↗
NASA NTRS1973

SAS-2 observations of gamma rays from the galactic plane

The SAS-2 gamma ray experiment has made measurements on the high energy gamma rays coming from the galactic center region. The gamma radiation in this region is very much more intense than in the anticenter region, in agreement with the observations made with the OSO-3 experiment of Kraushaar et al. (1973); and exhibits a narrow distribution along the plane which is nearly uniform in intensity from 330 deg to 30 deg. The energy spectrum in the range from 35 MeV to 210 MeV is quite flat, consistent with a cosmic ray-interstellar matter interaction pion-decay spectrum, or a mixture of this spectrum and a spectrum formed by Compton radiation from cosmic ray electrons. The intensity of the radiation in the anticenter direction is consistent with that expected from the cosmic ray-interstellar matter interaction origin, namely 0.000.002 photons.

Kniffen, D. A.↗
NASA NTRS1973

Cosmic ray electrons of E greater than 1 Gev - Some new measurements and interpretations.

In the summer of 1971 new measurements were made of the primary electron spectrum from 1 to 20 GeV with an electron spectrometer telescope at Fort Churchill. This telescope has been calibrated by using electrons and pions of 0.5 to 15 GeV at the Stanford Linear Accelerator in early 1971 and again in 1972. The calibration results suggest that the events observed are due to interactions of high-energy protons. The measured primary electron spectrum is uncomfortably close to that calculated for secondary electrons produced by the interaction of cosmic ray nuclei with interstellar hydrogen in the Galaxy, and therefore the question of the origin of the high-energy electrons is reopened. The problem of the age of cosmic ray electrons must also be reexamined if the measured spectrum is found to extend to still higher energies.

Webber, W. R.↗
NASA NTRS1973

The astrophysics of the diffuse background of X-rays and gamma rays

The orgin of diffuse X-ray and gamma ray background and some of the astrophysical implications of such a radiation background are discussed. Data show that gamma and X-rays come from thermal bremsstrahlung, neutral pion decay, and compton scattering of thermal protons. The range of energies studied extend from approximately 10 0 eV to approximately 10 to the 8th power eV.

Cowsik, R.↗