Ultra-Heavy Galactic Cosmic Ray Propagation and Atmospheric Corrections for SuperTIGER

SuperTIGER (Super Trans-Iron Galactic Element Recorder) is a balloon-borne instrument designed to directly measure ultra-heavy galactic cosmic-ray (UHGCR) nuclei. SuperTIGER had two successful Antarctic flights with float altitudes between ~36-40 km. Galactic cosmic-ray source (GCRS) abundances can be obtained by correcting SuperTIGER measured abundances to top-of-atmosphere (TOA) ones and propagating those through the interstellar medium. To obtain TOA abundances of UHGCR nuclei, the observed measurements are corrected using Geant4 simulations to understand the nuclear interactions and energy losses cosmic-ray nuclei experience propagating through the atmosphere. Results from these simulations are used to create a response matrix to describe the charge-changing losses or gains of cosmic-ray nuclei species. The simulation results are also used to obtain TOA energy thresholds of cosmic-ray nuclei to trigger SuperTIGER's detectors. These results are compared to the previous atmospheric propagation model used for TIGER and SuperTIGER TOA abundances. GCRS abundances are derived from TOA abundances by propagating assumed GCRS abundances through the interstellar medium via the leaky-box model with a Fisk-model correction for solar modulation and comparing the results with SuperTIGER TOA abundances. The assumed GCRS abundances are modified based on the results and this process is performed iteratively until the GCRS abundances produce TOA abundances that match SuperTIGER's.