Boron Isotopes in the PAMELA Experiment

Abstract

Analysis of the isotope composition of nuclei in galactic cosmic rays (GCR) in the PAMELA orbital international experiment allows studying the problems of cosmic-ray origin and propagation in our Galaxy. PAMELA magnetic spectrometer data provided the significant progress in the study of the light nuclei isotope composition of GCR from H to Be in the energy range ∼0.1–1 GeV/nucleon. This makes it possible to estimate the contribution of local (∼100 pc) young (∼106 years) interstellar sources (LISS) into GCR fluxes from supernova explosions. The analysis of boron (B) isotope fluxes in the GCR has so far been carried out only in the energy range ∼0.08–0.17 GeV/nucleon in the space experiments Voyager, Ulysses, ACE. In the present contribution the attempt was done to determine the 11B/10B ratio in the energy range ∼0.1–1.0 GeV/nucleon for the first time on the base of 2006–2014 PAMELA data using the measurements of the detected nuclei rigidities, velocities and ionization losses in a multilayer calorimeter. The new PAMELA results are consistent with existing as experimental data and those expected from simulations. However the statistical and systematic measurement uncertainties do not allow to separate the local boron source contributions into GCR fluxes. The preliminary results of the boron isotope flux analysis in GCR (10B, 11B spectra and 11B/10B ratio dependences on the rigidity and energy) are presented as well as the existing measurement data and simulation results.