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The Cosmic-Ray 3He/4He Ratio from 200 MeV per Nucleon−1 to 3.7 GeV per Nucleon−1

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© 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation O. Reimer et al 1998 ApJ 496 490 DOI 10.1086/305358

0004-637X/496/1/490

Abstract

The abundances of cosmic-ray helium isotopes between 0.2 and 3.7 GeV nucleon-1 were measured by the Isotope Matter Antimatter Experiment (IMAX) during a flight from Lynn Lake, Manitoba, Canada on 1992 July 16-17. The IMAX balloon-borne magnetic spectrometer realized a direct measurement of the charge, the velocity, and the rigidity of cosmic rays using plastic scintillators, a high-resolution time-of-flight system, and two silica-aerogel Cerenkov counters in conjunction with a drift chamber/multiwire proportional chamber tracking system. About 75,000 helium isotopes are identified by their mass using the velocity versus magnetic rigidity technique. The measured 3He/4He ratios are corrected to the top of the atmosphere, and a comparison with previous data is given. The observed isotopic composition is found to be generally consistent with the predictions of a standard leaky box model of cosmic-ray transport in the Galaxy.

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10.1086/305358