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MEASUREMENTS OF THE RELATIVE ABUNDANCES OF HIGH-ENERGY COSMIC-RAY NUCLEI IN THE TeV/NUCLEON REGION
Ahn, H. S.,Allison, P. S.,Bagliesi, M. G.,Barbier, L.,Beatty, J. J.,Bigongiari, G.,Brandt, T. J.,Childers, J. T.,Conklin, N. B.,Coutu, S.,DuVernois, M. A.,Ganel, O.,Han, J. H.,Jeon, J. A.,Kim, K. C.,L IOP Publishing 2010 The Astrophysical journal Vol.715 No.2
<P>We present measurements of the relative abundances of cosmic-ray nuclei in the energy range of 500-3980 GeV/nucleon from the second flight of the Cosmic Ray Energetics And Mass balloon-borne experiment. Particle energy was determined using a sampling tungsten/scintillating-fiber calorimeter, while particle charge was identified precisely with a dual-layer silicon charge detector installed for this flight. The resulting element ratios C/O, N/O, Ne/O, Mg/O, Si/O, and Fe/O at the top of atmosphere are 0.919 +/- 0.123(stat) +/- 0.030(syst), 0.076 +/- 0.019(stat) +/- 0.013(syst), 0.115 +/- 0.031(stat) +/- 0.004(syst), 0.153 +/- 0.039(stat) +/- 0.005(syst), 0.180 +/- 0.045(stat) +/- 0.006(syst), and 0.139 +/- 0.043(stat) +/- 0.005(syst), respectively, which agree with measurements at lower energies. The source abundance of N/O is found to be 0.054 +/- 0.013(stat) +/- 0.009(-0.017)(syst+0.010esc). The cosmic-ray source abundances are compared to local Galactic (LG) abundances as a function of first ionization potential and as a function of condensation temperature. At high energies the trend that the cosmic-ray source abundances at large ionization potential or low condensation temperature are suppressed compared to their LG abundances continues. Therefore, the injection mechanism must be the same at TeV/nucleon energies as at the lower energies measured by HEAO-3, CRN, and TRACER. Furthermore, the cosmic-ray source abundances are compared to a mixture of 80% solar system abundances and 20% massive stellar outflow (MSO) as a function of atomic mass. The good agreement with TIGER measurements at lower energies confirms the existence of a substantial fraction of MSO material required in the similar to TeV per nucleon region.</P>
ENERGY SPECTRA OF COSMIC-RAY NUCLEI AT HIGH ENERGIES
Ahn, H. S.,Allison, P.,Bagliesi, M. G.,Barbier, L.,Beatty, J. J.,Bigongiari, G.,Brandt, T. J.,Childers, J. T.,Conklin, N. B.,Coutu, S.,DuVernois, M. A.,Ganel, O.,Han, J. H.,Jeon, J. A.,Kim, K. C.,Lee, IOP Publishing 2009 The Astrophysical journal Vol.707 No.1
<P>We present new measurements of the energy spectra of cosmic-ray (CR) nuclei from the second flight of the balloon-borne experiment Cosmic-Ray Energetics And Mass (CREAM). The instrument included different particle detectors to provide redundant charge identification and measure the energy of CRs up to several hundred TeV. The measured individual energy spectra of C, O, Ne, Mg, Si, and Fe are presented up to similar to 10(14) eV. The spectral shape looks nearly the same for these primary elements and it can be fitted to an E(-2.66 +/- 0.04)power law in energy. Moreover, a new measurement of the absolute intensity of nitrogen in the 100-800 GeV/n energy range with smaller errors than previous observations, clearly indicates a hardening of the spectrum at high energy. The relative abundance of N/O at the top of the atmosphere is measured to be 0.080 +/- 0.025 (stat.) +/- 0.025 (sys.) at similar to 800 GeV/n, in good agreement with a recent result from the first CREAM flight.</P>
Performance of the CREAM-III Calorimeter
Moo Hyun Lee,Ho Seok Ahn,Ganel, O.,Ji Hye Han,Jeon, J.A.,Chan Ho Kim,Ki Chun Kim,Lutz, L.,Malinin, A.,GoWoon Na,Shinwoo Nam,Park, I.H.,Na Hee Park,Eun-Suk Seo,Vartanyan, A.,Walpole, P.,Jayoung Wu,Jong IEEE 2009 IEEE transactions on nuclear science Vol.56 No.3
<P>Cosmic Ray Energetics And Mass (CREAM) is a balloon-borne experiment to directly measure the elemental spectra of protons to iron nuclei with energies up to ~ 10<SUP>15</SUP> eV. Energies of these cosmic-ray particles are measured by an ionization calorimeter comprised of 20 layers of 1 radiation length thick tungsten plates and 20 layers of 0.5 mm diameter scintillating fibers. Each tungsten plate is 500 times 500 times 3.5 mm<SUP>3</SUP> and the fibers are grouped into fifty 1 cm wide ribbons. After construction, the CREAM-III calorimeter was tested at CERN, the European high energy physics lab, in the H2 beam line of the SPS. Following the CERN test, the calorimeter was integrated into the CREAM-III instrument, and flown successfully in the 3rd flight of the project, during the 2007/8 Antarctic campaign. We present the performance of the CREAM-III calorimeter in lab and beam tests.</P>