A Measurement of Cosmic Ray Deuterium from 0.2-3.0 GeV/nuc

The rare isotopes of hydrogen and helium, ^2H and ^3He, are believed to be produced predominantly from ^1H and ^4He interactions within the galactic interstellar medium. The unique history of these rare isotopes provides important constraints on galactic cosmic ray source spectra and propagation within the Galaxy. Hydrogen and helium isotopes were measured over a wide range in energy with the balloon-borne experiment, IMAX, which flew from Lynn Lake, Manitoba in 1992. Measurements of of ^1H and ^2H at balloon altitudes include a significant contribution of secondaries produced from interactions of ^1H and ^4He in the atmosphere, especially at low energies. An estimate of the atmospheric secondary ^1H and ^2H, obtained using the IMAX ascent data, is compared with previous calculations of atmospheric secondaries. The energy spectrum of ^2H, corrected for atmospheric secondaries, as well as previously published results of ^3He also obtained from IMAX measurements will be compared with predictions of cosmic ray galactic propagation models.