ATIC EXPERIMENT: ELEMENTAL SPECTRA FROM THE FLIGHT IN 2000

The Advanced Thin Ionization Calorimeter (ATIC) program files a fully active Bismuth Germanate (BGO) calorimeter preceded by a 0.75 interaction length graphite target with a silicon charge detector, to measure the charge and energy of cosmic ray nuclei. ATIC is intended to measure elemental spectra of nuclei from hydrogen to iron, with energies from ∼ 30 GeV - 100 TeV. ATIC has been flown in two Long Duration Balloon (LDB) flights in 2000 and 2002. In this paper we present preliminary results from the first flight, which was a test flight that lasted for 16 days, starting on 12/28/00. ATIC is a balloon borne experiment designed to investigate the charge and energy spectra of Z = 1 to 28 cosmic rays over the energy range ∼ 30 GeV - 100 TeV. ATIC collected 45 GB of science data during its first LDB flight in Antarctica from 12/28/00 to 01/13/01. In this paper we present a brief description of ongoing analysis and preliminary energy spectra of protons and helium. Various issues that arose in extracting elemental spectra from the first flight are discussed.