The 7 Li/ 6 Li ratio in the energy range from 150 to 1300 MeV/nucleon measured with the balloon-borne ISOMAX98 instrument in the upper atmosphere

We report on the measured 7 Li/ 6 Li ratio at an atmospheric depth of 4.6 g/cm 2 in the energy range from 183 to 1314 MeV/nucleon, using the Isotope Magnet Experi- ment (ISOMAX). This balloon-borne magnetic spectrometer in combination with a Time-of-Flight system (TOF) and a silica-aerogel Cherenkov detector was built to measure the isotopic composition of the light elements (3 Z 8) in the cosmic radiation up to several GeV/nucleon. ISOMAX was flown on August 4-5, 1998, from Lynn Lake, Manitoba, Canada. The data was collected during 13 hours at an alti- tude which corresponds to a residual atmosphere of less than 5 g/cm 2 . The results on 10 Be/ 9 Be ratio are presented in the these proceedings by Hams et al. (2001) in the TOF regime and by de Nolfo et al. (2001) in the Cherenkov regime.