Prospects for high energy light isotope measurements on balloons

A number of recent 'anomalies' detected in the cosmic-ray flux have underscored the importance of improving our understanding of cosmic-ray source and propagation processes. To this end, one of the key observational tasks is obtaining measurements of the relative abundances of the light cosmic-ray isotopes at relativistic energies (above -1 GeV/n), where existing information is extremely scarce. In particular, measurements of the clock isotope 10Be for a range of relativistic time dilations are urgently needed. However, such measurements present a severe experimental challenge. The required mass resolution can only be reached if magnetic spectrometers with strong magnetic fields are equipped with state-of-the-art high-resolution trackers, and combined with devices such as ring-imaging Cherenkov counters for precise velocity measurements. Additionally, large exposure factors are needed for good statistical accuracy. In this presentation, we will briefly review the goals and challenges of such measurements, and describe a new proposed instrument, HELIX (the High-Energy Light Isotope eXperiment), that is designed to meet these challenges on a long-duration balloon flight.