Joint Astrophysics Colloquium

Unraveling the Cosmic-ray Spectrum : Measurements with high altitude Balloons

Patrick (Jojo) Boyle

McGill University

The balloon-borne cosmic-ray detector TRACER (“Transition Radiation for Cosmic Radiation”) was designed to measure cosmic-ray nuclei with single element resolution up to high energies, and to facilitate a large geometric aperture by utilizing a transition radiation detector. TRACER was launched in two long-duration balloon flights, in Antarctica (2003), and subsequently, after significant upgrades, from Kiruna, Sweden (2006). The data cover the elements from boron (Z=5) to iron (Z=26), and reach energies in excess of 10¹⁴ eV/particle. The results provide constraints on the elemental abundance and spectral slope at the cosmic-ray source and on the propagation of cosmic rays through the interstellar medium.

Here, I will discuss what it takes to fly the largest and heaviest cosmic-ray detector ever flown on a high-altitude balloon. I will present new results on the abundance of secondary elements such as boron, and will discuss our results with an eye on the recent gamma-ray measurements of supernova remnants by FERMI and VERITAS. Finally, I will briefly discuss the potential of the TRACER technique for future investigations.