Measurement of Cosmic-Ray Nuclei with the Third Flight of the CREAM Balloon-Borne Experiment

Abstract

. CREAM-III was designed to directly measure the elemental spectra of cosmic-ray nuclei from Hydrogen to Iron in the energy range from 10 12 to 10 15 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. Conference -ICRC2017 10-20 July, 2017 Bexco, Busan, Korea † Speaker 35th International Cosmic Ray PoS(ICRC2017)198Cosmic-Ray Nuclei with CREAM-III J. R. Smith 2 1. Introduction CREAM (Cosmic Ray Energetics And Mass) is a balloon experiment designed to perform direct measurements of cosmic-ray composition and energy spectra above the atmosphere. The goal of this multi-mission experiment is to collect sufficient statistics to explore the region of energies up to 10 15 eV and test the current models of cosmic-ray acceleration and propagation in the Galaxy. The third CREAM payload (CREAM-III) was launched from McMurdo on December 19, 2007 and landed on January 17 2008, for a 29 day flight. The balloon circumnavigated the Antarctic continent twice and floated at an altitude ~38 km with an atmospheric overburden of 3.9 ± 0.4 g/cm 2 . One of the primary scientific goals of the CREAM project is the measurement of secondary cosmic-ray nuclei at high energies. Secondary nuclei are those which are produced predominantly through spallation interactions of primary nuclei, those produced in the cosmicray source regions. Because these spallation interactions are thought to occur primarily during the propagation of primary nuclei in the interstellar medium, a measurement of the ratio of secondary to primary fluxes reveals information about the propagation history (e.g., the amount of material traversed) of the primary particles In this paper, results from the on-going analysis of the data from the third flight are reported. The results presented in this paper are preliminary.