All-particle spectrum measured by ATIC-1
The Advanced Thin Ionization Calorimeter (ATIC), a balloon-borne experiment, is designed to investigate the composition and energy spectra of cosmic rays of charge Z = 1 to 26 over the energy range 1011 - 1014 eV. The instrument consists of a silicon matrix charge detector, plastic scintillator strip hodoscopes interleaved with graphite interaction targets, and an 18 radiation length deep, fully active bismuth germanate (BGO) calorimeter. ATIC has had two successful long-duration balloon (LDB) flights launched from McMurdo Station, Antarctica in 2000 and 2002. In this paper, we present the all-particle spectrum and the average mass number spectrum extracted from data collected during the first flight, and compare them with results from other direct and indirect experiments.