GALACTIC COSMIC-RAY CONFINEMENT TIME - ULYSSES HIGH-ENERGY TELESCOPE MEASUREMENTS OF THE SECONDARY RADIONUCLIDE BE-10

We report new measurements of the isotopic abundances of the Galactic cosmic-ray isotopes Be-7, Be-9, and radioactive Be-10. These measureme nts from the Ulysses High Energy Telescope (HET) combine exceptional m ass resolution with superior statistics. Measurements of radioisotopes produced as secondaries during cosmic-ray propagation provide estimat es of the average density of material traversed by the cosmic rays and , within the context of the ''leaky box'' model, the confinement time of cosmic rays in the Galaxy. Be-10, with its long lifetime (tau(1/2) = 1.6 x 10(6) yr by beta(-) decay) and pure secondary origin, is parti cularly well suited to this purpose. The HET measurement yields a dens ity of rho = 0.19 +/- 0.03 atoms cm(-3), corresponding to a confinemen t time of 26(-5)(+4) Myr. Measurements of the shorter lived cosmic-ray radioisotopes Al-26 and Cl-36, including the results from the HET rep orted elsewhere (by Connell ansi coworkers), complement these Be-10 re sults and provide a broader view of cosmic-ray propagation.