SuperTIGER Abundances of Galactic Cosmic Rays for the Atomic Number (Z) Interval 30 to 56





Citation of Original Publication

“SuperTIGER Abundances of Galactic Cosmic Rays for the Atomic Number (Z) Interval 30 to 56,” N. E. Walsh for the SuperTIGER Collaboration, Proceedings of Science: 37th International Cosmic Ray Conference, (Berlin, Germany), 118 (2021).


This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
Public Domain Mark 1.0



SuperTIGER (Super Trans-Iron Galactic Element Recorder) is a long-duration-balloon instrument that completed its first Antarctic flight during the 2012-2013 austral summer, spending 55 days at an average float altitude of 125,000 feet. SuperTIGER measured the relative abundances of Galactic cosmic-ray (GCR) nuclei with high statistical precision and well resolved individual element peaks from 10Ne to 40Zr. SuperTIGER also made exploratory measurements of the relative abundances up to 56Ba. Although the statistics are low for elements heavier than 40Zr, we present preliminary relative abundance measurements of charges Z=41−56 with individual element resolution. GCR measurements up to 40Zr support a source acceleration model where supernovae in OB associations preferentially accelerate refractory elements that are more readily embedded in interstellar dust grains than volatiles. In addition, injection into the GCR for both refractory and volatile elements appears to follow a charge dependence consistent with their grain sputtering cross sections. Our preliminary measurements of the Z=41−56 range suggest the existence of an alternative GCR source or acceleration model for Z>40 elements. We report progress in refining this interesting result.