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Published 1999 | Published
Book Section - Chapter Open

Radioactive Clock Isotope Abundance Measurements from the CRIS Experiment aboard the ACE Spacecraft


Radioactive cosmic ray nuclei produced by nuclear interactions during cosmic ray propagation through the galaxy can be used to study the mean interstellar gas density in the propagation volume and the time scales associated with the propagation process. The Cosmic Ray Isotope Spectrometer (CRIS) aboard the Advanced Composition Explorer (ACE) has made high-resolution abundance measurements of the beta-decay secondary isotopes ^(10)Be, ^(26)Al, ^(36)Cl, and ^(54)Mn over the energy range 70-400 MeV/nuc. The large geometrical factor of CRIS (~250 cm^2sr) and the 20 months of data collection at near solar minimum conditions have made it possible since launch in August, 1997 to accumulate data samples considerably larger than previous missions. The isotopic abundances derived from these data are presented and compared with previous measurements.

Additional Information

© University of Utah. Provided by the NASA Astrophysics Data System. This research was supported by NASA at California Institute of Technology (grant NAGS-6912), Jet Propulsion Laboratory, Goddard Space Flight Center, and Washington University.

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