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

Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer / Aguilar, M., Ali Cavasonza, L., Ambrosi, G., Arruda, L., Attig, N., Bachlechner, A., Barao, F., Barrau, A., Barrin, L., Bartoloni, A., Basegmez-Du Pree, S., Battiston, R., Becker, U., Behlmann, M., Beischer, B., Berdugo, J., Bertucci, B., Bindi, V., De Boer, W., Bollweg, K., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 123:18(2019). [10.1103/PhysRevLett.123.181102]

Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer

Rozza D.;
2019-01-01

Abstract

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of He-3 and He-4 fluxes are presented. The measurements are based on 100 million He-4 nuclei in the rigidity range from 2.1 to 21 GV and 18 million He-3 from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the He-3 and He-4 fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the He-3/He-4 flux ratio is measured for the first time. Below 4 GV, the He-3/He-4 flux ratio was found to have a significant long-term time dependence. Above 4 GV, the He-3/He-4 flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law proportional to R-Delta with Delta = 0.294 0.004. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.
2019
Properties of Cosmic Helium Isotopes Measured by the Alpha Magnetic Spectrometer / Aguilar, M., Ali Cavasonza, L., Ambrosi, G., Arruda, L., Attig, N., Bachlechner, A., Barao, F., Barrau, A., Barrin, L., Bartoloni, A., Basegmez-Du Pree, S., Battiston, R., Becker, U., Behlmann, M., Beischer, B., Berdugo, J., Bertucci, B., Bindi, V., De Boer, W., Bollweg, K., et al.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 123:18(2019). [10.1103/PhysRevLett.123.181102]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11388/232935
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