The High Energy Light Isotope eXperiment (HELIX) project is a new NASA supported instrument aiming to make definitive measurements of rare nuclear isotopes in the flux of energetic cosmic rays impinging the earth. Of special interest are the 10Be and 9Be isotopes of beryllium, which track the production and propagation of “secondary” cosmic rays, produced by interactions of heavier elements during propagation through the Milky Way Galaxy. Understanding these isotopes will lead to refinements of models of secondary processes, which are critical in interpreting the apparent excess of cosmic antimatter reported by space-borne instruments in recent years (and in particular the possibility that this excess may be due to dark matter particles). The HELIX payload is under assembly at the University of Chicago with a system of time-of-flight detectors contributed by Penn State’s group of S. Coutu (these are used to measure the charge and relativistic speed of incident nuclei). Other state-of-the-art instruments on this payload include a superconducting magnet spectrometer (University of Michigan and Indiana University) and a ring-imaging Cherenkov detector (University of Chicago, Chiba University, McGill University and Queen’s University), with trigger detectors contributed by Northern Kentucky University and data acquisition electronics by Ohio State University. The instrument is slated to fly by high-altitude balloon in Antarctica in late 2021. See http://helix.uchicago.edu/ .

P. Allison et al., “Cosmic Ray Isotope Measurement with HELIX,” Proceedings of the 36th International Cosmic Ray Conference, Madison, WI (2019), https://pos.sissa.it/358/121/pdf