ISOMAX: Flight Performance of the Isotope Magnet Experiment

ISOMAX, a new balloon-borne cosmic ray instrument developed to measure the isotopic composition of the light elements in the cosmic radiation, was flown for the first time on August 4-5, 1998, from Lynn Lake, Manitoba, Canada. The main purpose of the ISOMAX program is to obtain the ratio of radioactive 10Be to stable 9Be over a wide range of energies, and consequently a wide range of time-dilation factors. Configured for its first flight, ISOMAX has a geometry factor of 450 cm^2sr and uses a large, high-field, superconducting magnet in conjunction with state-of-the-art tracking, time-of-flight, and Cherenkov detectors to measure light isotopes with a mass resolution better than 0.25 amu over the ~0.2-1.7 Ge V /nucleon energy range. In the 1998 flight, the maximum detectable rigidity of the ISO MAX magnetic spectrometer was 970 GV/c for He at 60% of the full magnetic field. ISOMAX returned over 16 hours of data from altitudes of more than 36 km as well as considerable data from lower altitudes. In this paper, a description of the instrument and initial isotopic results will be presented. The performance and results from the individual detector systems are discussed in other papers presented at this meeting