This proposal seeks support for the continuation of a new suborbital program (helix the high-energy light isotope experiment) designed to make measurements of the isotopic composition of light…

This proposal seeks support for the continuation of a new suborbital program (helix the high-energy light isotope experiment) designed to make measurements of the isotopic composition of light cosmic-RAY nuclei from ~200 MEV/NUC to ~10 GEV/NUC. Past measurements of this kind have provided profound insights into the nature and origin of cosmic rays revealing for instance information on acceleration and confinement time scales and exposing some conspicuous discrepancies between solar and cosmicray abundances. The most detailed information currently available comes from the ACE/cris mission but is restricted to energies below a few 100 MEV/NUC. Helix aims at extending this energy range by over an order of magnitude where in many cases no fully resolved measurements exist and where relativistic time dilation affects the apparent lifetime of radioactive clock nuclei. The helix measurements will provide essential information for understanding the propagation history of cosmic rays in the galaxy. This is crucial for properly interpreting several intriguing anomalies reported in recent cosmic-RAY measurements pertaining to the energy spectra of protons helium and heavier nuclei and to the anomalous rise in the positron fraction at higher energy. The primary scientific goals of the full helix program are: - a high-statistics measurement of the 10BE/9BE 'clock ratio' to ~10 GEV/NUC - a high-statistics measurement of the 3HE/4HE ratio to ~12GEV/NUC - the first measurements of 22NE/20NE above 1 GEV/NUC - the first mass-resolved measurements of 7LI/6LI and 10B/11B above 1 GEV//NUC a number of secondary goals will also be pursued including the measurement of several other isotopic and elemental abundance ratios and fluxes the proposed work will be conducted by a team of US scientists and engineers with extensive experience in cosmic-RAY observations on balloons or in space and specifically in magnet spectroscopy with the smili p-bar and heat programs. Significant participation from a crew of more than 10 graduate post-graduate and undergraduate students forms an important educational element of the program.