L.A. Khein

Advanced Thin Ionization Calorimeter (ATIC) balloon experiment: expected performance

An advanced thin ionization calorimeter (ATIC) will be used to investigate the charge composition and energy spectra of ultrahigh energy primary cosmic rays in a series of long- duration balloon flights. While obtaining new high priority scientific results, this balloon payload can also serve as a proof of concept for a BGO calorimeter-based instrument on the International Space Station. The ATIC technical details are presented in a companion paper at this conference. Here we discuss the expected performance of the instrument based on a GEANT code developed for simulating nuclear- electromagnetic cascades initiated by protons. For simulations of helium and heavy nuclei, a nucleus-nucleus interaction event generator LUCIAE was linked to the GEANT based program. Using these models, the design of the ATIC detector system has been optimized by simulating the instrument response to particles of different charges over the energy range to be covered. Results of these simulations are presented and discussed.

Advanced thin ionization calorimeter to measure ultrahigh energy cosmic rays

Abstract An Advanced Thin Ionization Calorimeter (ATIC) will be used to investigate the charge composition and energy spectra of primary cosmic rays over the energy range from about 10 10 to >10 14 eV in a series of long-duration balloon flights. The totally active BGO calorimeter, 22 radiation length thick, will measure the electromagnetic energy ensuing from nuclear interactions in a one interaction length thick carbon target. Trajectory information will be obtained from the location of the cascade axis in the BGO calorimeter and in the segmented scintillator layers of the upstream carbon target. The highly segmented charge module comprised of scintillator strips, a silicon matrix, and a Cherenkov array will minimize the effect of backscattered particles on primary charge measurements. While obtaining new high priority scientific results, the ATIC balloon payload can also serve as a proof of concept, or engineering model, for a BGO calorimeter-based instrument on the International Space Station. We examine the added advantage of locating such an experiment for long durations on a platform such as the Space Station.

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.