Analysis Progress: SuperTIGER Abundances of Galactic Cosmic Rays for the Atomic Number (Z) Interval 40 to 56

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. 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. Although statistics are low for elements heavier than ₄₀Zr, our preliminary measurements of the ₄₀Zr to ₅₆Ba range suggest the existence of an alternative GCR source or acceleration model for these rare elements. We report progress in refining this interesting result.