Measurement of cosmic-ray nuclei with the third flight of the CREAM balloon-borne experiment

Abstract

The balloon-borne Cosmic Ray Energetics And Mass experiment had its third flight (CREAM-III) over Antarctica for 29 days from December 17, 2007 to January 19, 2008. CREAM-III was designed to directly measure the elemental spectra of cosmic-ray nuclei from Hydrogen to Iron in the energy range from 1012 to 1015 eV. Energy of incident cosmic rays was measured with a calorimeter that consisted of a densified carbon target directly above a stack of 20 alternating layers of tungsten and scintillating fiber ribbons. Multiple charge measurements were independently made with the silicon charge detector (SCD), Cherenkov Camera (CherCam), and a Timing Charge Detector (TCD) in order to identify particles and minimize backscattering effects from the calorimeter. Compared to previous CREAM flights, the electronic noise of CREAM-III was reduced, significantly lowering the energy threshold. Results from on-going analysis of the energy spectra will be presented.