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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

An investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances

An instrument, the Caltech High Energy Isotope Spectrometer Telescope was developed to measure isotopic abundances of cosmic ray nuclei by employing an energy loss - residual energy technique. A detailed analysis was made of the mass resolution capabilities of this instrument. A formalism, based on the leaky box model of cosmic ray propagation, was developed for obtaining isotopic abundance ratios at the cosmic ray sources from abundances measured in local interstellar space for elements having three or more stable isotopes, one of which is believed to be absent at the cosmic ray sources. It was shown that the dominant sources of uncertainty in the derived source ratios are uncorrelated errors in the fragmentation cross sections and statistical uncertainties in measuring local interstellar abundances. These results were applied to estimate the extent to which uncertainties must be reduced in order to distinguish between cosmic ray production in a solar-like environment and in various environments with greater neutron enrichments.

Wiedenbeck, M. E.↗
NASA NTRS1978

A cosmic ray isotope spectrometer

The paper describes a new instrument to be flown on ISEE-C which is optimized to measure the isotopic composition of solar and galactic cosmic rays in the 5-250 MeV/nucleon range. A mass resolution of not greater than 0.3 AMU should be achieved for all elements with charge Z not exceeding 30.

Althouse, W. E.↗
NASA NTRS1979

Cometary particulate analyzer

A concept for determining the relative abundance of elements contained in cometary particulates was evaluated. The technique utilizes a short, high intensity burst of laser radiation to vaporize and ionize collected particulate material. Ions extracted from this laser produced plasma are analyzed in a time of flight mass spectrometer to yield an atomic mass spectrum representative of the relative abundance of elements in the particulates. Critical aspects of the development of this system are determining the ionization efficiencies for various atomic species and achieving adequate mass resolution. A technique called energy-time focus, which utilizes static electric fields to alter the length of the ion flight path in proportion to the ion initial energy, was used which results in a corresponding compression to the range of ion flight times which effectively improves the inherent resolution. Sufficient data were acquired to develop preliminary specifications for a flight experiment.

Friichtenicht, J. F.↗
NASA NTRS1978

Small mass spectrometer with extended measurement capabilities at high pressures

For the in situ investigation of planetary atmospheres a small Mattauch-Herzog mass spectrometer has been developed. Its high-pressure performance has been improved by incorporating differential pumping between the ion source and the analyzing fields, shortening the path-length as well as increasing the extraction field in the ion source. In addition doubly ionized and dissociated ions are used for mass analysis. These measures make possible operation up to 0.01 millibars. Results of laboratory tests related to linearity, dynamic range, and mass resolution are presented, in particular for CO2.

Von Zahn, U.↗
NASA NTRS1978

Measurements of the isotopic composition of cosmic-ray nuclei with Z=10-14

Measurements are reported of the isotopic composition of cosmic-ray nuclei with Z=10-14 using a Cerenkov x total energy technique. These measurements are for an energy interval 40-120 MeV/nuc at a typical energy of about 500 MeV/nuc at the top of the atmosphere. The mass resolution sigma varies between 0.4 and 0.5 AMU in this charge range. A total of about 450 events are analyzed for their isotopic composition. These studies indicate that the isotopic composition of these elements at the source must be very similar to the known solar abundances.

Simpson, G. A.↗
NASA NTRS1979

The isotopic composition of solar flare accelerated neon

The individual isotopes of neon in energetic solar-flare particles have been clearly resolved with a rms mass resolution of 0.20 amu. The ratios found are Ne-20/Ne-22 = 7.6 (+2.0, -1.8) and Ne-21/Ne-22 of no more than about 0.11 in the 11-26 MeV per nucleon interval. This isotopic composition is essentially the same as that of meteoritic planetary neon-A and is significantly different from that of the solar wind.

Mewaldt, R. A.↗
NASA NTRS1979

The isotopes of neon in the galactic cosmic rays

The paper examines the results obtained by the University of Chicago instrument on board the IMP 7 satellite used to measure the abundances of Ne-20 and Ne-22 in the galactic cosmic rays during 1973-1977, over the general energy range of 60-230 MeV per nucleon. It is reported that the instrument shows a mass resolution of 0.7 amu(sigma) which was confirmed by calibrating a backup instrument at the LBL Bevalac with separated beams of neon isotopes. Through the use of standard solar modulation and cosmic-ray propagation models, the cosmic-ray source ratio inferred is Ne-22/Ne-20 = 0.38 = or -0.07 which is significantly greater than the present solar system ratio. It is concluded that propagation effects or cross-section uncertainties cannot account for such a large abundance of Ne-22, and thus this measurement provides evidence that the cosmic rays come from a source region where the Ne-22 abundance is substantially greater than in solar system material.

Garcia-Munoz, M.↗
NASA NTRS1980

A thermalized ion explosion model for high energy sputtering and track registration

A velocity spectrum of neutral sputtered particles as well as a low resolution mass spectrum of sputtered molecular ions was measured for 4.74 MeV F-19(+2) incident of UF4. The velocity spectrum is dramatically different from spectra taken with low energy (keV) bombarding ions, and is shown to be consistent with a hot plasma of atoms in thermal equilibrium inside the target. A thermalized ion explosion model is proposed for high energy sputtering which is expected to describe track formation in dielectric materials. The model is shown to be consistent with the observed total sputtering yield and the dependence of the yield on the primary ionization rate of the incident ion.

Seiberling, L. E.↗
NASA NTRS1979

Satellite measurements of the isotopic composition of galactic cosmic rays

The individual isotopes of galactic cosmic ray Ne, Mg, and Si at 100 MeV/nucleon were clearly resolved with an rms mass resolution of 0.20 amu. The results suggest the cosmic ray source is enriched in Ne-22, Mg-25, and Mg-26 when compared to the solar system. The ratio of (Mg-25)+(Mg-26) to Mg-24, which is approximately 0.49 compared to the solar system value of 0.27, suggest that the cosmic ray source and solar system material were synthesized under different conditions.

Mewaldt, R. A.↗
NASA NTRS1979

Solar and terrestrial noble gases in magnetospheric precipitation

Metal-foil collectors were installed on the external structure of Skylab to entrap precipitating magnetospheric particles. The foils were retrieved, and the entrapped helium, neon, and argon were isotopically analyzed in a high-resolution mass spectrometer. Solar and terrestrial helium and neon and terrestrial argon were detected. As expected, the isotopic composition of neon and argon in the high atmosphere was found to be strongly fractionated. Special techniques were used to estimate the initial particle energy of He-3. The measured He-3 flux is consistent with the assumption that precipitating solar He-3 is the major source of terrestrial He-3.

Lind, D. L.↗
NASA NTRS1981

A balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon and nitrogen

The isotopic compositions of galactic cosmic ray boron, carbon, and nitrogen were measured at energies near 300 MeV amu, using a balloon-borne instrument at an atmospheric depth of approximately 5 g/sq cm. The calibrations of the detectors comprising the instrument are described. The saturation properties of the cesium iodide scintillators used for measurement of particle energy are studied in the context of analyzing the data for mass. The achieved rms mass resolution varies from approximately 0.3 amu at boron to approximately 0.5 amu at nitrogen, consistent with a theoretical analysis of the contributing factors. Corrected for detector interactions and the effects of the residual atmosphere the results are B-10/B=0.33 (+0.17, -0.11), C-13/C=0.06 (+0.13, -0.11), and N-15/N=0.42 (+0.19, -0.17). A model of galactic propagation and solar modulation is described. Assuming a cosmic ray source composition of solar-like isotopic abundances, the model predicts abundances near Earth consistent with the measurements.

Zumberge, J. F.↗
NASA NTRS1980

A measurement of the isotopic composition of galactic cosmic ray carbon, nitrogen and oxygen

The paper reports the results of an investigation of the isotopic composition of galactic cosmic ray carbon, nitrogen and oxygen (80-230 MeV/amu) made using the U.C. Berkeley HKH instrument aboard the ISEE-3 spacecraft. The combination of high mass resolution and a large statistical sample makes possible a precise determination of the relative isotopic abundances for these elements. In local interplanetary space the following values are found: C-13/C = 0.067 + or - 0.008, N-15/N = 0.54 + or - 0.03, O-17/O less than 0.027, and O-18/O - 0.019 + or - 0.003.

Wiedenbeck, M. E.↗
NASA NTRS1980

Satellite measurements of the isotopic composition of galactic cosmic rays

The individual isotopes of galactic cosmic ray Ne, Mg, and Si at about 100 MeV/nucleon have been resolved with an rms mass resolution of about 0.20 amu. The results suggest that the cosmic ray source is enriched in Ne-22, Mg-25, and Mg-26 when compared to the solar system. It is suggested that the cosmic ray source and solar system material were synthesized under different conditions.

Mewaldt, R. A.↗
NASA NTRS1981

Development of a fast ion mass spectrometer for space research

An ion mass spectrometer having a cylindrical E bar x B bar analyzer and either a cylindrical or spherical electrostatic analyzer is described. The instrument has two nested channels and a postacceleration between the electrostatic and E bar x B bar analyzers for wide ranges of energy and mass responses. It is noted that the dual-channel construction not only doubles the data acquisition rate but also permits a reversal of the electrostatic field orientation in the inner channel for lighter ions. The outer channel is then optimized for ions of medium to high mass numbers, resulting in increased mass resolution for such heavy ions. When combined with a cylindrical E bar x B bar analyzer, a 90-deg-deflection angle spherical electrostatic analyzer provides an extremely wide viewing angle. The angular distribution of ions can be derived from such geometry if a position-sensitive resistive anode or a detector array is used at the exit aperture. Details on the principles of operation, the instrument design, and calibration are presented.

Hahn, S. F.↗
NASA NTRS1982

The isotopes of H through C in galactic cosmic rays

The charge, energy spectra, and isotopic composition of hydrogen through nitrogen have been studied with the GSFC/UNH cosmic ray experiments on board the Pioneer 10 and 11 spacecraft. Good charge and mass resolution have been obtained by utilizing three parameter analysis (i.e., two measurements of delta E and a measurement of the residual kinetic energy of stopping particles). This method allows isotopic resolution for the High Energy Telescope (HET) which operates over a typical energy range of 30-56-MeV/nuc for He. The observations will be over solar quiet times from September 1976-September 1977. The resolution, methods of analysis, spectra, and isotopic composition will be presented and discussed where the statistical significance of H to C isotopes is meaningful.

Smith, B.↗
NASA NTRS1982

Magnetic deflection ion mass spectrometer experiment for atmosphere explorer

The magnetic ion mass spectrometer was carried aboard Atmosphere Explorer C and Atmosphere Explorer D. The instrument measures the relative abundance of ionic species with very high sensitivity and very high mass resolution. Thus isotopic ratios for various ion species can be examined and minor ion species such as O(++), N(++), and H(+) can be detected when their relative abundance is very small. These instruments functioned with no critical internal failures but the premature loss of the AE-D spacecraft after only a few months of operation has led to an emphasis of scientific achievement from AE-C. The very long lifetime of AE-C coupled with the prolonged time that this spacecraft spent near the F-region peak led to the accumulation of very large count numbers in the channeltron detectors.

Hoffman, J. H.↗
NASA NTRS1983

An accelerator test of semi-empirical cross-sections

Experimentally measured yields of isotopes of elements from Mg to K resulting from the fragmentation of Ar-40 are compared with calculated yields based on semiempirical cross-section formulas. Excellent mass resolution is obtained in measurements using a beam of 287 MeV/amu Ar-40 incident on a CH2 target. The resolution is made possible by an Si(Li) detector telescope. Whereas the general agreement between calculation and experiment is good, with an rms difference of approximately 24 percent, attention is called to certain significant differences. It is found that important information for refining the semiempirical calculation of fragmentation cross sections can be obtained from data collected during the calibration of cosmic ray detector systems when such calibrations are performed under suitable conditions.

Lau, K. H.↗