Cosmic ray tracks in the Shalka meteorite |
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Authors: | R.K. Bull S.A. Durrani |
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Affiliation: | Department of Physics, University of Birmingham, Birmingham Great Britain |
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Abstract: | Track densities of heavy cosmic rays have been studied in hypersthene crystals taken from seven known depths below a fusion crust in the Shalka meteorite. By comparing these with a theoretical model, a preatmospheric radius of 20 ± 2cm has been estimated for the meteorite, assuming it to have been originally spherical. The fossil track-length distributions show a prominent peak in the region of 12–15 μm; and this has been attributed, on the basis of accelerated-ion calibration experiments, to cosmic ray Fe ions. The value (≥0.38 ± 0.04) of relative abundance of Fe ions to the total Fe-group ions (20 ≤ Z. ≤ 28) found in the cosmic ray flux averaged over the last ~19 m.y. is shown to be broadly similar to those given by present-day measurements. |
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