Since the discovery of cosmic rays in 1911, studies to unravel the sources, acceleration, and propagation of cosmic rays have long captivated the field of astrophysics. Among these cosmic rays, the rare beryllium (7Be, 9Be, 10Be) and lithium isotopes (6Li, 7Li) hold a special place. These light nuclei are secondaries, which mainly originate from the interaction of carbon, nitrogen, and oxygen nuclei with the interstellar medium (ISM). Therefore, measurements of the spectra or the isotopic composition of beryllium and lithium provide significant constraints on CRs source composition, acceleration, and CRs transport in the Galaxy.
The Alpha Magnetic Spectrometer (AMS) operating on the International Space Station (ISS) is a cutting-edge detector that can measure quantities including the charge, velocity, and rigidity of cosmic rays, enabling the measurements of light isotope compositions. Understanding the abundance of lithium and beryllium isotopes is crucial for studying cosmic ray (CR) propagation models due to their distinct characteristics. In space, (7Be) remains stable as the electron density in the galaxy is not sufficient for it to capture an electron and dacay. (9Be) is stable, but (10Be) has a half-life of 1.387 ±0.012 (0.87%) Ma., comparable to the expected cosmic-ray residence time in the galaxy. The knowledge of the relative abundance of 10 Be/9 Be determines galactic halo size. This characteristic of beryllium isotopes provide valuable insights into CR propagation models. (6Li) is believed to be produced purely by interactions between galactic CRs and the interstellar medium (ISM), while it is thought that (7Li) might have additional sources such as stellar production and primordial nucleosynthesis. The knowledge of the abundance of lithium isotopes will shed light on the origin of lithium in CRs.
In this thesis, the measurement of the beryllium isotope fluxes from 0.51 GeV/n to 12.1 GeV/n and lithium isotope fluxes from 0.41 GeV/n to 11.5 GeV/n, based on events collected during the first 11.5 years (May 2011 to November 2022) operations of AMS are presented.
