Light Isotope Measurements from the ISOMAX 98 Experiment

Measurements of light cosmic ray isotopes (2<= Z <= 8) have been carried out by the Isotope Magnet Experiment (ISOMAX) balloon-borne magnetic spectrometer, during a flight from Lynn Lake, Manitoba, Canada in August 1998. The main emphasis of the ISOMAX experiment is to determine the ratio of radioactive ^10Be to stable ^9Be at energies where time-dilation becomes significant, in order to distinguish among models of cosmic ray transport. ISOMAX employs state-of-the-art time-of-flight (TOF) and Cherenkov velocity detectors and a precision magnetic-rigidity spectrometer composed of a high-field superconducting magnet and an advanced drift-chamber tracking system. For the ISOMAX 98 flight, the maximum detectable rigidity was about 1 TV/c and the geometric acceptance was 450 cm^2sr. With a TOF resolution better than 65 ps and aerogel Cherenkov radiators with indices of refraction n=1.14, light isotopes are well resolved to more than 1.5 GeV/nucleon. ISOMAX 98 elemental and isotopic results will be presented in this paper.