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  • 1995-1999  (8)
  • 1995  (8)
  • 1
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    Direct production of electron-positron pairs by 200-GeV/nucleon oxygen and sulfur ions in nuclear emulsion (1995)
    American Physical Society
    Details
    Publication Date: 1995-02-01
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Physical Society
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    PAPER CURRENT
  • 2
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    Be-10 in terrestrial bauxite and industrial aluminum: An LDEF fallout (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Work has continued on the search for Be-10 on metals other than aluminum flown on LDEF. Much time-consuming extractive chemistry has been performed at Rutgers University on turnings obtained from the ends of two stainless steel trunnions from LDEF and the prepared samples will be run on the University of Pennsylvania accelerator mass spectrometer. We have continued to investigate our discovery of naturally-occurring Be-10 contamination in bauxite and industrial aluminums from different sources. Measurements of Be-10 in ores from three different sites, and from four different samples of commercial aluminum have been made. Our investigators indicate that the contamination in commercial aluminum metal originates in its principal ore, bauxite. The levels in some bauxite samples were much greater than the maximum possible for in situ production by cosmic ray secondaries. Absorption of atmospheric Be-10 by surface ores exposed to rainfall is a reasonable explanation.
    Keywords: METALLIC MATERIALS
    Type: NASA. Langley Research Center, LDEF: 69 Months in Space. Third Post-Retrieval Symposium, Part 1; p 227-230
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Absorbed dose and LET spectra measurements on LDEF (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Total absorbed doses measured with TLD's, linear energy transfer (LET) spectra measured with plastic track detectors, and low energy neutrons measured on LDEF have been compared with model calculations. The total absorbed doses measured in TLD's were higher than predicted in the calculations of Armstrong et al. and differ from the calculations of Atwell et al. LDEF LET spectra are dependent on detector orientation, shielding and experiment location. These factors need to be taken into account when modeling the LDEF LET spectra. LET spectra measured with plastic nuclear track detectors (PNTD's) also deviate significantly from calculations especially for high LET particles (LET(sub infinity) H2O greater than 100keV/micron). Modeling efforts to date do not include the contribution of proton induced secondaries. Analysis of polycarbonate PNTD's from the West-side of LDEF has revealed a very high fluence of tracks (greater than 1 x 10(exp 7) tracks/cm(exp 2) under 2 gm/cm(exp 2) shielding). Fluence drops off rapidly as shielding depth increases. Tracks only form in the region of the detector closest to the surface, not in the bulk of the detector. To date no adequate explanation for this observation has been found. We plan to measure range distribution of very high LET (LET (sub infinity) H2O greater than 500 keV/micron) secondary particles produced in silicon wafer by high energy primary cosmic ray particles. Refinements of experimental techniques and model calculations are being carried out in order to understand existing discrepancies between experimental measurements and calculations.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: NASA. Langley Research Center, LDEF: 69 Months in Space. Third Post-Retrieval Symposium, Part 1; p 135-148
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    NASA TECHNICAL REPORTS
  • 4
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    Linear Energy Transfer (LET) spectra of cosmic radiation in low Earth orbit (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Integral linear energy transfer (LET) spectra of cosmic radiation (CR) particles were measured on five Cosmos series spacecraft in low Earth orbit (LEO). Particular emphasis is placed on results of the Cosmos 1887 biosatellite which carried a set of joint U.S.S.R.-U.S.A. radiation experiments involving passive detectors that included thermoluminescent detectors (TLD's), plastic nuclear track detectors (PNTD's), fission foils, nuclear photo-emulsions, etc. which were located both inside and outside the spacecraft. Measured LET spectra are compared with those theoretically calculated. Results show that there is some dependence of LET spectra on orbital parameters. The results are used to estimate the CR quality factor (QF) for the COSMOS 1887 mission.
    Keywords: SPACE RADIATION
    Type: San Francisco Univ., High LET, Passive Space Radiation Dosimetry and Spectrometry; 6 p
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    NASA TECHNICAL REPORTS
  • 5
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    Space radiation dosimetry on US and Soviet manned missions (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Radiation measurements obtained on board U.S. and Soviet spacecraft are presented and discussed. A considerable amount of data has now been collected and analyzed from measurements with a variety of detector types in low-Earth orbit. The objectives of these measurements have been to investigate the dose and Linear Energy Transfer (LET) spectra within the complex shielding of large spacecraft. The shielding modifies the external radiation (trapped protons, electrons, cosmic ray nuclei) which, in turn, is quite dependent on orbital parameters (altitude, inclination). For manned flights, these measurements provide a crew exposure record and a data base for future spacecraft design and flight planning. For the scientific community they provide useful information for planning and analyzing data from experiments with high sensitivity to radiation. In this paper, results of measurements by both passive and active detectors are described. High-LET spectra measurements were obtained by means of plastic nuclear track detectors (PNTD's) while thermoluminescent dosimeters (TLD's) measured the dose.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: San Francisco Univ., High LET, Passive Space Radiation Dosimetry and Spectrometry; 68 p
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    NASA TECHNICAL REPORTS
  • 6
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    Cosmic ray LET spectra and doses on board Cosmos-2044 biosatellite (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Results of the experiments on board Cosmos-2044 (Biosatellite 9) are presented. Various nuclear track detectors (NTD) (dielectric, AgCl-based, nuclear emulsions) were used to obtain the Linear Energy Transfer (LET) spectra inside and outside the satellite. The spectra from the different NTDs have proved to be in general agreement. The results of LET spectra calculations using two different models are also presented. The resultant LET distributions are used to calculate the absorbed and equivalent doses and the orbit-averaged quality factors (QF) of the cosmic rays (CR). Absorbed dose rates inside (approximately 20 g cm (exp -2) shielding) and outside (1 g cm(exp -2) the spacecraft, omitting electrons, were found to be 4.8 and 8.6 mrad d (exp -1), respectively, while the corresponding equivalent doses were 8.8 and 19.7 mrem d(exp -1). The effects of the flight parameters on the total fluence of, and on the dose from the CR particles are analyzed. Integral dose distributions of the detected particles are also determined. The LET values which separate absorbed and equivalent doses into 50% intervals are estimated. The CR-39 dielectric NTD is shown to detect 20-30% of the absorbed dose and 60-70% of the equivalent dose in the Cosmos-2044 orbit. The influence of solar activity phase on the magnitude of CR flux is discussed.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: San Francisco Univ., High LET, Passive Space Radiation Dosimetry and Spectrometry; 8 p
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    NASA TECHNICAL REPORTS
  • 7
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    Depth distribution of absorbed dose on the external surface of Cosmos 1887 biosatellite (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Significant absorbed dose levels exceeding 1.0 Gy day(exp -1) have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLD's) made in U.S.S.R. and U.S.A. The dose was found to decrease rapidly with increasing absorber thickness, thereby indicating the presence of intensive fluxes of low-energy particles. Comparison between the U.S.S.R. and U.S.A. results and calculations based on the Vette Model environment are in satisfactory agreement. The major contribution to the dose under thin shielding thickness is shown to be from electrons. The fraction of the dose due to protons and heavier charged particles increases with shielding thickness.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: San Francisco Univ., High LET, Passive Space Radiation Dosimetry and Spectrometry; 4 p
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    NASA TECHNICAL REPORTS
  • 8
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    Direct Production of Electron-Positron Pairs by 200-GeV/Nucleon Oxygen and Sulfur Ions in Nuclear Emulsion (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Measurements of direct Coulomb electron-positron pair production have been made on the tracks of relativistic heavy ions in nuclear track emulsion. Tracks of 0(16) and S(32) at 200 GeV/nucleon were studied. The measured total cross sections and energy and emission angle distributions for the pair members are compared to theoretical predictions. The data are consistent with some recent calculations when knock-on electron contamination is accounted for.
    Keywords: Atomic and Molecular Physics
    Type: NASA-TM-111920 , NAS 1.15:111920 , Physical Review A; 51; 2; 1253-1259
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    NASA TECHNICAL REPORTS
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