Li and Be Isotopes in the PAMELA Experiment from Flight Data for 2006–2014

Abstract

The results are presented from measuring the isotopic composition of lithium and beryllium nuclei in galactic cosmic rays with energies of up to ~1 GeV/nucleon, obtained with the best statistical and methodical reliability in the PAMELA orbital experiment in 2006–2014. The time-of-flight analysis of nuclei in a scintillation telescope and an analysis of the distributions of ionization losses of the nuclei in the tracker and multilayer calorimeter of the PAMELA magnetic spectrometer with the rigidity known from measuring the path in the magnet gap are used. The analysis uses the results from GEANT4 modeling of the distribution of the time of flight and the ionization losses of nuclear isotopes in the calorimeter with a rigidity step of 0.2 GV, which are in good agreement with the corresponding experimental distributions. Nuclear charges are determined from the scintillation telescope data of the PAMELA magnetic spectrometer. The spectra of ⁶Li, ⁷Li, ⁷Be, ⁹Be, and ¹⁰Be isotopes are obtained, depending on their rigidity, energy, and ratios. The results from measurements are compared to existing experimental and calculated data. Based on new data on the isotopic composition of Li and Be nuclei, the contribution from local light-nucleus sources from recent (~1 million years) nearby (~100 ps) supernova explosions to the intensity of galactic cosmic rays is estimated for the first time.