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Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of $^3\mathrm{He}$ and $^4\mathrm{He}$ fluxes are presented. The measurements are based on 100 million $^4\mathrm{He}$ nuclei in the rigidity range from 2.1 to 21 GV, and 18 million $^3\mathrm{He}$ from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the $^3\mathrm{He}$ and $^4\mathrm{He}$ fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the $^3\mathrm{He}/^4\mathrm{He}$ flux ratio is measured for the first time. Below 4 GV, the $^3\mathrm{He}/^4\mathrm{He}$ flux ratio was found to have a significant long-term time dependence. Above 4 GV, the $^3\mathrm{He}/^4\mathrm{He}$ flux ratio was found to be time independent and its rigidity dependence is well described by a single power law ${\propto R^{\Delta}}$ with ${\Delta = -0.294 \pm 0.004}$. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.

 

Phys. Rev. Lett. 123, 181102 (2019)
(a) The time-averaged $^3\mathrm{He}/^4\mathrm{He}$ flux ratio as a function of rigidity R (red points) with statistical and uncorrelated systematic errors added in quadrature. (b) The $^3\mathrm{He}/^4\mathrm{He}$ flux ratio spectral index (red points) as a function of R.

AMS-02 Publications

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Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer
Phys. Rev. Lett. 123, 181102 (2019), View supplemental material and data
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Towards Understanding the Origin of Cosmic-Ray Electrons
Phys. Rev. Lett.122, 101101 (2019), Citations: 10, View supplemental material and data
Published on: Editors' Suggestion
Towards Understanding the Origin of Cosmic-Ray Positrons
Phys. Rev. Lett. 122, 041102 (2019), Citations: 32, View supplemental material and data
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Precision Measurement of Cosmic-Ray Nitrogen and its Primary and Secondary Components with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett.121, 051103 (2018), Citations: 19, View supplemental material and data
Published on: Editors' Suggestion
Observation of Complex Time Structures in the Cosmic-Ray Electron and Positron Fluxes with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 121, 051102 (2018), Citations: 23, View supplemental material and data
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Observation of Fine Time Structures in the Cosmic Proton and Helium Fluxes with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 121, 051101 (2018), Citations: 26, View supplemental material and data
Published on: Editors' Suggestion Featured in Physics
Observation of New Properties of Secondary Cosmic Rays Lithium, Beryllium, and Boron by the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett.120, 021101 (2018), Citations: 61, View supplemental material and data
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Observation of the Identical Rigidity Dependence of He, C, and O Cosmic Rays at High Rigidities by the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 119, 251101 (2017), Citations: 66, View supplemental material and data
Published on: Editors' Suggestion Featured in Physics
Precision Measurement of the Boron to Carbon Flux Ratio in Cosmic Rays from 1.9 GV to 2.6 TV with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett.117, 231102 (2016), Citations: 166, View supplemental material and data
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Antiproton Flux, Antiproton-to-Proton Flux Ratio, and Properties of Elementary Particle Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett.117, 091103 (2016), Citations: 265, View supplemental material and data
Published on: Editors' Suggestion
Precision Measurement of the Helium Flux in Primary Cosmic Rays of Rigidities 1.9 GV to 3 TV with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett.115, 211101 (2015), Citations: 261, View supplemental material and data
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Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 114, 171103 (2015), Citations: 472, View supplemental material and data
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Precision Measurement of the (${\rm e}^+$ + ${\rm e}^−$) Flux in Primary Cosmic Rays from 0.5 GeV to 1 TeV with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 113, 221102 (2014), Citations: 236, View supplemental material and data
Published on: Editors' Suggestion Featured in Physics
Electron and Positron Fluxes in Primary Cosmic Rays Measured with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 113, 121102 (2014), Citations: 439, View supplemental material and data
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High Statistics Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5 – 500 GeV with the Alpha Magnetic Spectrometer on the International Space Station
Phys. Rev. Lett. 113, 121101 (2014), Citations: 482, View supplemental material and data
Published on: Editors' Suggestion Featured in Physics Physics Viewpoint
First Result from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5–350 GeV
Phys. Rev. Lett. 110, 141102 (2013), Citations: 983, View supplemental material and data

* Citation information from High-Energy Physics Literature Database.