| The Cosmic Ray Energetics And Mass (CREAM) experiment is a balloon-borne, high energy particle detector designed to measure cosmic ray nuclei from protons through Iron at energies up to 1015 eV. It has succeeded in measuring this broad range of charge and energy through multiple Antarctic flights, data from the first of which will be presented here, using complementary charge and energy detectors. These included a Timing Charge Detector (TCD), a Transition Radiation Detector (TRD), a Silicon Charge Detector (SCD), and a Calorimeter. The TRD and Calorimeter provide both tracking and an energy determination. The TCD and SCD provide excellent charge resolution, of order 0.2 e. Together, these have enabled us to construct absolute spectra for individual primary nuclei, Carbon, Oxygen, Neon, Magnesium, Silicon, and Iron, as well as the less abundant secondary, Nitrogen. Our spectra agree well with previous measurements, and for several nuclei extend to the highest energies yet measured. The well-resolved charge species have also permitted us to form the secondary to primary ratios of Boron to Carbon and Nitrogen to Oxygen, also up to the highest energies measured and in agreement with previous data. Since charged particles like cosmic rays bend in magnetic fields which permeate our galaxy, traditional pointing astronomy is not possible. Instead, we use the spectra and ratios to provide us with clues to cosmic rays' origins, acceleration mechanism, and propagation history. In particular, the CREAM I Boron to Carbon ratio fits a propagation model with index of delta = 0.5 - 0.6 while the CREAM II primary nuclei spectra all have an index of 2.66 +/- 0.04. This last suggests that they all have the same acceleration mechanism, and after accounting for propagation energy loss consistent with the Boron to Carbon ratio, that the mechanism is likely Fermi first order acceleration. Finally, Nitrogen serves as a particularly useful test bed for these findings. Its ratio with Oxygen is consistent with a small amount of Nitrogen existing in the cosmic ray source, ∼ 10% with respect to the source's Oxygen content, given propagation conditions again based on the Boron to Carbon ratio. At the highest energies, this source flux is seen, as expected, to emerge over the secondary flux in the Nitrogen spectrum itself. |
