A balloon measurement of the isotopic composition of galactic cosmic ray iron
The isotopic composition of galactic cosmic ray iron in the energy interval of approximately 1550 to 2200 MeV/nucleon was measured using a balloon-borne mass spectrometer. The instrument was flown from Palestine, Texas, in May 1984 for greater than 35 hours at an atmospheric depth of approximately 6 g/sq cm. Masses were derived by the Cerenkov-Energy technique. The Cerenkov counter employed a silica aerogel radiator with an index of refraction n = 1.1. Particle energies were measured in a stack of NaI(Tl) scintillators, which also provided particle trajectories. A detailed discussion of the sources of mass uncertainty is presented, including an analytic model of the contribution from fluctuations in the Cerenkov yield from knock-on electrons. The achieved mass resolution is approximately 0.65 amu, which is consistent with the theoretical estimate. An Fe-54/Fe-56 abundance ratio of 0.14(sup +0.18)(sub -0.11) and an 84 percent confidence upper limit of Fe-58/Fe-56 is less than or = to 0.07 at the top of the atmosphere is reported. Combining the data with those of precious measurements of the composition of iron at lower energies, and using a model of the galactic propagation, cosmic-ray source abundance ratios of Fe-54/Fe-56 = 0.064(sup +0.032)(sub -0.027) and Fe-58/F3-56 is less than or = to 0.062 were derived. These values are consistent with the composition of solar system iron and place restrictions on the conditions under which cosmic-ray iron is synthesized.
- Research Organization:
- California Inst. of Tech., Pasadena, CA (USA)
- OSTI ID:
- 6719929
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
COSMIC NUCLEI
ISOTOPE RATIO
MASS SPECTRA
ABUNDANCE
CHEMICAL COMPOSITION
CHERENKOV RADIATION
ELECTRONS
EXPERIMENTAL DATA
IRON
MATHEMATICAL MODELS
REFRACTIVITY
SOLAR SYSTEM
COSMIC RADIATION
DATA
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
INFORMATION
IONIZING RADIATIONS
LEPTONS
METALS
NUCLEI
NUMERICAL DATA
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SPECTRA
TRANSITION ELEMENTS
640105* - Astrophysics & Cosmology- Galaxies