Cosmic rays are energetic particles from extraterrestrial sources traveling very close to the speed of light. They are undoubtedly produced from energetic processes in the universe, but their origin is not completely understood more than 100 years after their discovery. The IPST Cosmic Physics Group develops particle detectors for balloon-borne and space-based experiments to investigate cosmic ray origin, acceleration and propagation. They provide direct measurements of cosmic rays over more than six orders of magnitude (factor of a million) in energy. These instruments have been used to search for exotic sources, such as dark matter and antimatter, and to explore a possible limit to particle acceleration in supernova. The in-house laboratory for the Cosmic Ray Energetics and Mass (CREAM) instrument development, integration, and flight operations provide valuable hands-on training for undergraduate and graduate students as well as young scientists and engineers. Building on the six successful balloon flights of CREAM over Antarctica for a record-breaking 161 days of exposure, the payload has been transformed for exposure on the International Space Station (ISS). This project, dubbed ISS-CREAM (pronounced “ice cream”) would increase our data collection by an order of magnitude to reach the highest energy practical with direct measurements.
Our other projects include the Advanced Thin Ionization Calorimeter (ATIC) long-duration balloon experiment, the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) study, the Balloon-borne Experiment with a Superconducting magnet Spectrometer (BESS), and the Alpha Magnet Spectrometer (AMS) on the ISS. The latter has been taking data successfully at the rate of ~16 billion events per year since its launch to the ISS in 2011. One highlight of the AMS results is the puzzling excess of high-energy positrons. The possibility of this excess coming from the annihilation of dark matter particles has generated a lot of excitement, but currently other astrophysical explanations cannot be ruled out. In order to characterize the excess, it is critical to extend precise measurements to higher energies, and understand cosmic ray propagation and acceleration.
