Constraints on Cosmic-Ray Acceleration and Transport from Isotope Observations
M. E. Wiedenbeck1, W. R. Binns2, E. R. Christian3, A. C. Cummings4, 
J. S. George4, P. L. Hink2, J. Klarmann2, R. A. Leske4, M. Lijowski2, 
R. A. Mewaldt4, S. M. Niebur2, E. C. Stone4, T. T. von Rosenvinge3, 
and N. E. Yanasak4

1 Jet Propulsion Laboratory, Pasadena, CA, USA
2 Washington University, St. Louis, MO, USA
3 NASA/Goddard Space Flight Center, Greenbelt, MD, USA
4 California Institute of Technology, Pasadena, CA, USA

The Cosmic Ray Isotope Spectrometer (CRIS) on ACE is providing isotopically-resolved measurements of essentially all nuclides in the range 2<=Z<=30 at energies of a few hundred MeV/nucleon. In most cases, statistics are sufficient to permit investigations of the energy dependence of the composition as well. This data set is being used to address a variety of topics related to the acceleration and transport of galactic cosmic rays. The elemental source composition is being investigated to probe the fractionation process that leads to the preferential enhancement of refractory (or low-FIP) elements in the accelerated material. Radioactive isotopes are being used to determine the residence time of nuclei in the interstellar medium before acceleration to high energies and the confinement time of the accelerated particles prior to escape from the Galaxy. Electron- capture secondary nuclides are being used as indicators of energy- changing processes that may affect the cosmic ray spectra after the main phase of acceleration has occurred. Stable secondaries are being studied for the information they can provide on the distribution of the matter traversed by cosmic rays during transport. We will discuss recent progress that has been made in a number of these areas through the use of ACE/CRIS data.