Precision Measurement of Lithium Flux in Cosmic Rays with the Alpha Magnetic Spectrometer on the International Space Station

Abstract

Lithium nuclei in cosmic rays are produced by the spallation of heavier cosmic rays on the interstellar medium. Thus, the abundance of lithium constitutes a very sensitive observable for the modeling of cosmic rays propagation in the Galaxy. A precision measurement of the lithium flux with rigidities from 2 GV to 3 TV by AMS, is presented.

Latest results from the Alpha Magnetic Spectrometer on the International Space Station

“…Prior to AMS, data on the lithium flux was limited as shown in Figure 48. The current status of the AMS lithium flux measurement based on 1.5 million events is shown in Figure 49 together with the results of previous experiments [5]. …”

On the spectrum of stable secondary nuclei in cosmic rays

“…The AMS-02 measurement suggests that the B/C ratio drops with energy as E −1/3 k at high energies, in perfect agreement with the naive expectation based on a Kolmogorov spectrum of Galactic turbulence, although this conclusion depends somewhat on the threshold energy above which the fit is calculated. On the other hand, preliminary data from AMS-02 also suggest that the spectrum of lithium, a secondary nucleus that in many respects is expected to behave as boron, shows a pronounced hardening at rigidity above a few hundred GV (Derome 2016;Yan 2017), with a high energy slope of the spectrum that appears to be very similar to that of primary nuclei, in apparent contradiction with the secondary nature of lithium. Since these measurements are going to be used in the near future to test different models of CR propagation, it seems timely to make an assessment of the different reasons why the naive expectation for secondary nuclei might need to be revisited.…”