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Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer
Name
PhysRevLett.123.181102.pdf
Description
Published version
Size
352.68 KB
Format
Adobe PDF
Checksum (MD5)
ac1762ef101ff8f726070dfb3734f1fa
Date Issued
2019
Journal
Physical Review Letters
Publisher
American Physical Society (APS)
Version
Final published version
Abstract
© 2019 authors. Published by the American Physical Society. Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of He3 and He4 fluxes are presented. The measurements are based on 100 million He4 nuclei in the rigidity range from 2.1 to 21 GV and 18 million He3 from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the He3 and He4 fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the He3/He4 flux ratio is measured for the first time. Below 4 GV, the He3/He4 flux ratio was found to have a significant long-term time dependence. Above 4 GV, the He3/He4 flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law ∈RΔ with Δ=-0.294±0.004. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.
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Creative Commons Attribution 4.0 International license
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DOI of Published Version
10.1103/PHYSREVLETT.123.181102
