Measurement of light isotopes ratios in the cosmic rays with the IMAX balloon experiment

This thesis is dedicated to the measurement of hydrogen isotopic abundances in the cosmic rays with energies between 0.2 to 1.8 GeV/nuc. The data for the analysis discussed here were obtained during a high-altitude balloon flight of the Isotope Matter Antimatter eXperiment (IMAX), on 16-17 July 1992 from Lynn Lake, Canada. The results that this analysis aims to provide should enlarge the data basis for distinguishing among various models about galactic cosmic rays propagation. From this perspective, the deuteron-to-helium and deuteron-to-proton ratios are resolved from the flight data, as it is generally believed that the cosmic deuterons are mainly created from the interaction of the helium and proton nuclei with the interstellar medium. Another result of interest provided by this work is the ratio triton-to-helium, measured at 5 g · cm −2 atmospheric overburden. Tritium is considered as being produced in the atmosphere mainly from the spallation of helium nuclei. Thus, the 3 H/ 4 He ratio can serve as test for the present calculations about atmospheric secondary tritons. IMAX measurement technique employs a simultaneous determination of charge, velocity and magnetic rigidity. The analysis of the separate detectors is concentrated on rigidity determination, Time-of-Flight calibration and charge selection. Ratios of the light isotopes in the instrument are obtained by means of mass histograms simulations. Further instrumental and atmospheric corrections are applied to the measured ratios and the results at the top of the atmosphere are compared with predictions from theoretical models.