We report abundances of elements from 26 Fe to 40 Zr in the cosmic radiation measured by the SuperTIGER (TransIron Galactic Element Recorder) instrument during 55 days of exposure on a long-duration balloon flight over Antarctica. These observations resolve elemental abundances in this charge range with single-element resolution and good statistics. These results support a model of cosmic ray origin in which the source material consists of a mixture of -+ 19 6 11 % material from massive stars and ∼81% normal interstellar medium material with solar system abundances. The results also show a preferential acceleration of refractory elements (found in interstellar dust grains) by a factor of ∼4 over volatile elements (found in interstellar gas) ordered by atomic mass (A). Both the refractory and volatile elements show a mass-dependent enhancement with similar slopes.

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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 10 Ne to 40 Zr. SuperTIGER also made exploratory measurements of the relative abundances up to 56 Ba. Although the statistics are low for elements heavier than 40 Zr, we present preliminary relative abundance measurements of charges = 41 − 56 with individual element resolution. GCR measurements up to 40 Zr 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 = 41 − 56 range suggest the existence of an alternative GCR source or acceleration model for > 40 elements. We report progress in refining this interesting result.

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TIGERISS is an Ultra-Heavy Galactic Cosmic Ray (UHGCR) detector to be proposed to the NASA Astrophysics Pioneers Program capable of measuring the abundance relative to 26 Fe of every element from 5 B to 82 Pb. It is evolved from the LDB TIGER and SuperTIGER balloon instruments and the Heavy-Nuclei Explorer SMEX, and compared to its predecessors, TIGERISS will have a greatly improved capability to definitively identify UHGCR nuclei. This has been demonstrated in component accelerator tests at CERN, including silicon strip detectors in place of scintillators. The geometry factor for TIGERISS is estimated to be from 1.1 to 1.7 m 2 sr depending on the ISS attachment point, compared to 0.6 m 2 sr for TIGER. Within one-year TIGERISS would observe ∼27 56 Ba nuclei, a 20% statistically significant result comparable to the current SuperTIGER data set. Not requiring corrections for atmospheric interactions and scintillator saturation effects the TIGERISS results would be cleaner, and they would also make preliminary measurements to higher charges that will test models for cosmic-ray origins and acceleration. TIGERISS will measure UHGCR nuclei resulting from neutron-capture nucleosynthesis in heavy stars, supernovae, and binary neutron-star mergers and will probe the relative contribution of r-process elements to the cosmic rays.