D. Granger

First results from ATIC beam-test at CERN

Abstract The Advanced Thin Ionization Calorimeter (ATIC) balloon-borne experiment will fly on several 10-day Long Duration Balloon (LDB) flights from McMurdo Station, Antarctica. Its main goal is cosmic-ray elemental spectra measurement from 50 GeV to 100 TeV for nuclei from hydrogen to iron. In September 1999 the ATIC detector was exposed to high-energy beams at CERNs SPS accelerator, within the framework of the development program for the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS). We present initial results from these beam-tests, including energy resolutions for electrons and protons at several beam energies from 100 GeV to 375 GeV. Results on signal linearity and collection efficiency estimates are also presented. We show how these results compare with expectations based on simulations, and their expected impacts on mission performance.

ATIC as a testbed for the ACCESS baseline calorimeter

The Advanced Thin Ionization Calorimeter (ATIC) balloon experiment is designed to measure the spectrum of individual elements from H through Fe up to a total energy >1014 eV. To accomplish this goal, ATIC incorporates a Silicon matrix detector composed of more than 4,000 pixels to measure the incident particle charge in the presence of backscatter background, three plastic scintillator hodoscopes to provide an event trigger as well as a backup measurement of the particle charge and trajectory, a 3/4 interaction length carbon target and a fully active ionization calorimeter composed of 22 radiation lengths of Bismuth Germanate (BGO) crystals. This detector complement is very similar to the baseline calorimeter for the Advanced Cosmic Ray Composition Experiment for the Space Station, ACCESS. The ATIC flights can be used to evaluate such a calorimeter in the cosmic ray “beam.” ATIC integration is currently underway with a first flight expected during 1999. This talk will discuss ATIC as it applies to ACCESS.