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Observation of ^(60)Fe in the Galactic Cosmic Rays

Israel, M. H. and Binns, W. R. and Christian, E. R. and Cummings, A. C. and de Nolfo, G. A. and Lave, K. A. and Leske, R. A. and Mewaldt, R. A. and Stone, E. C. and von Rosenvinge, T. T. and Wiedenbeck, M. E. (2015) Observation of ^(60)Fe in the Galactic Cosmic Rays. In: 34th International Cosmic Ray Conference (ICRC2015). Proceedings of Science. No.236. SISSA , Trieste, Italy, Art. No. 275.

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The Cosmic Ray Isotope Spectrometer (CRIS) on the ACE spacecraft has been measuring the isotopic composition of Galactic Cosmic Rays (GCRs) since August 1997. Using selected data from the past seventeen years, we have a set of 2.95 x 10^5 ^(56)Fe nuclei in the energy interval ~240 to ~470 MeV/nucleon with excellent mass resolution characterized by σ = 0.24 amu. In this data set we have detected fifteen well resolved ^(60)Fe nuclei. ^(60)Fe is β^- unstable with a half-life of 2.6 million years. The detection of these radioactive nuclei permits us to set an upper limit of a few million years on the time between nucleosynthesis of these nuclei and their acceleration to cosmic-ray energies. A lower limit of ~10^5 years was established by the CRIS observation that the electron-capture isotope ^(59)Ni is essentially absent in the GCRs. These two limits bracket the nucleosynthesis-to-acceleration time to a range that is consistent with the emerging evidence that the bulk of GCRs are accelerated in associations of massive stars (OB associations).

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Israel, M. H.0000-0002-8104-208X
Binns, W. R.0000-0001-6110-3407
Christian, E. R.0000-0003-2134-3937
Cummings, A. C.0000-0002-3840-7696
de Nolfo, G. A.0000-0002-3677-074X
Leske, R. A.0000-0002-0156-2414
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Wiedenbeck, M. E.0000-0002-2825-3128
Alternate Title:Observation of 60Fe in the Galactic Cosmic Rays
Additional Information:Copyright owned by the author(s) under the term of the Creative Commons Attribution-NonCommercial-ShareAlike.
Group:Space Radiation Laboratory
Series Name:Proceedings of Science
Issue or Number:236
Record Number:CaltechAUTHORS:20180828-122925311
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89237
Deposited By: George Porter
Deposited On:30 Aug 2018 21:58
Last Modified:16 Nov 2021 00:33

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