A measurement of the energy spectra and relative abundance of the cosmic-ray H and He isotopes over a broad energy range

The measurements reported of these isotopes were made using two sets of detectors during the same minimum modulation period in 1977. One measurement was made with a balloon-borne telescope, the other with telescopes on the Voyager spacecraft. It is noted that together they provide the widest energy range yet available for studying these isotopes: 14-150 MeV per nucleon for H2 and 10-290 MeV per nucleon for He-3. The simultaneous helium isotope observations are used to give a mutually consistent picture of galactic propagation and solar modulation. The data define the form of the interstellar H-1 and He-4 spectra, an interstellar matter path length for both H-1 and He-4, and a total residual modulation for He-4. The H-2 observations suggest a picture that is very similar for the galactic propagation of H-1 and He-4.